From 38c5e9e4cbe52c8693b11608cd850385716845e1 Mon Sep 17 00:00:00 2001
From: Laura Kasian <lkasian@synopsys.com>
Date: Fri, 28 Aug 2026 12:11:51 -0700
Subject: [PATCH 1/8] add per-part write path to the dataset registry

---
 .../viewer/vtk/datasets/visor_dataset.py      |  14 +-
 .../vtk/datasets/visor_dataset_registry.py    | 180 ++++++++++++++++-
 .../datasets/test_visor_dataset_registry.py   | 190 ++++++++++++++++++
 3 files changed, 382 insertions(+), 2 deletions(-)

diff --git a/src/ansys/visor/viewer/vtk/datasets/visor_dataset.py b/src/ansys/visor/viewer/vtk/datasets/visor_dataset.py
index 8ba4b8d3..b91ff35a 100644
--- a/src/ansys/visor/viewer/vtk/datasets/visor_dataset.py
+++ b/src/ansys/visor/viewer/vtk/datasets/visor_dataset.py
@@ -88,7 +88,19 @@ def list_variables(self) -> List[VisorPartVariables]:
         return result
 
     def set_state(self, new_state: PersistedDatasetState) -> None:
-        """Set the state of the dataset."""
+        """
+        Set the state of the dataset from persisted, name-keyed part state.
+
+        This is the persisted-state conversion path: it converts
+        new_state.parts (keyed by part name) into this dataset's runtime
+        state (keyed by part ID) via persisted_to_runtime_state.
+
+        Note: a second, id-keyed replacement path also exists, on the
+        registry rather than here: VisorDatasetRegistry.replace_part_states
+        replaces a dataset's .state directly with an already-runtime,
+        id-keyed RuntimeDatasetState, without going through this method or
+        its name-to-id conversion.
+        """
         self.state = self.persisted_to_runtime_state(new_state.parts)
 
     def mark_clean(self) -> None:
diff --git a/src/ansys/visor/viewer/vtk/datasets/visor_dataset_registry.py b/src/ansys/visor/viewer/vtk/datasets/visor_dataset_registry.py
index 0b7e4d90..1ada79a5 100644
--- a/src/ansys/visor/viewer/vtk/datasets/visor_dataset_registry.py
+++ b/src/ansys/visor/viewer/vtk/datasets/visor_dataset_registry.py
@@ -6,7 +6,10 @@
 from ansys.visor.viewer.core.metadata import ExtendedMetadata
 from ansys.visor.viewer.core.visor_logging import VisorDefaultLogger
 from ansys.visor.viewer.core.visor_types import VisorDatasetType
-from ansys.visor.viewer.models.runtime.dataset.runtime_dataset_state import RuntimeDatasetState
+from ansys.visor.viewer.models.runtime.dataset.runtime_dataset_state import (
+    RuntimeDatasetState,
+    RuntimePartProperties,
+)
 from ansys.visor.viewer.vtk.datasets.visor_dataset import VisorDataset
 from ansys.visor.viewer.vtk.variables.visor_part_variables import VisorPartVariables
 from ansys.visor.viewer.vtk.variables.visor_variable_update import VisorVariableUpdate
@@ -106,6 +109,181 @@ def remove(self, dataset_id: int) -> None:
         if dataset_id in self.datasets:
             self.datasets.pop(dataset_id)
 
+    # ------------------------------------------------------------------
+    # Per-part state: write path
+    # ------------------------------------------------------------------
+
+    def find_dataset_id_for_part(self, part_id: int) -> int | None:
+        """
+        Find the ID of the dataset that owns the given part.
+
+        Args:
+            part_id (int): The scene-graph node ID identifying the part.
+
+        Returns:
+            int | None: The dataset ID that owns the part, or None if no
+            dataset in the registry has this part_id in its PartIndex.
+        """
+        for dataset_id, dataset in self.datasets.items():
+            if part_id in dataset.part_index.part_ids:
+                return dataset_id
+        return None
+
+    def get_part_state(self, part_id: int) -> RuntimePartProperties | None:
+        """
+        Get the current runtime state record for a single part.
+
+        This is a read-only lookup: unlike the setters, it does not upsert
+        a record for a part that has no state yet.
+
+        Args:
+            part_id (int): The scene-graph node ID identifying the part.
+
+        Returns:
+            RuntimePartProperties | None: The live state record for the
+            part, or None if part_id resolves to no dataset, or the owning
+            dataset has no recorded state for it.
+        """
+        dataset_id = self.find_dataset_id_for_part(part_id)
+        if dataset_id is None:
+            return None
+        return self.datasets[dataset_id].state.part_states.get(part_id)
+
+    def _get_or_create_part_state(self, part_id: int) -> RuntimePartProperties | None:
+        """
+        Resolve the live part-state record for part_id, upserting if needed.
+
+        If the owning dataset has no part_states entry yet for part_id (e.g.
+        a freshly added dataset with no persisted part state), a
+        RuntimePartProperties(id=part_id) record is created and inserted
+        into the dataset's part_states dict first. This is mandatory: a
+        freshly added dataset has an empty part_states dict, so without
+        this upsert every setter would silently no-op for it.
+
+        Returns:
+            RuntimePartProperties | None: The live state record, or None if
+            part_id resolves to no dataset.
+        """
+        dataset_id = self.find_dataset_id_for_part(part_id)
+        if dataset_id is None:
+            return None
+        dataset = self.datasets[dataset_id]
+        part_state = dataset.state.part_states.get(part_id)
+        if part_state is None:
+            part_state = RuntimePartProperties(id=part_id)
+            dataset.state.part_states[part_id] = part_state
+        return part_state
+
+    def set_part_visibility(self, part_id: int, visible: bool) -> bool:
+        """
+        Set whether a part is visible.
+
+        Returns:
+            bool: True when the record was written, False when part_id
+            resolves to no dataset. Never raises.
+        """
+        part_state = self._get_or_create_part_state(part_id)
+        if part_state is None:
+            return False
+        part_state.visible = visible
+        return True
+
+    def set_part_opacity(self, part_id: int, opacity: float) -> bool:
+        """
+        Set a part's opacity.
+
+        Returns:
+            bool: True when the record was written, False when part_id
+            resolves to no dataset. Never raises.
+        """
+        part_state = self._get_or_create_part_state(part_id)
+        if part_state is None:
+            return False
+        part_state.opacity = opacity
+        return True
+
+    def set_part_diffuse_color(self, part_id: int, diffuse_rgb: list[float] | None) -> bool:
+        """
+        Set a part's custom diffuse colour, or clear it with None.
+
+        Returns:
+            bool: True when the record was written, False when part_id
+            resolves to no dataset. Never raises.
+        """
+        part_state = self._get_or_create_part_state(part_id)
+        if part_state is None:
+            return False
+        part_state.diffuse_rgb = diffuse_rgb
+        return True
+
+    def set_part_selected(self, part_id: int, selected: bool) -> bool:
+        """
+        Set whether a part is selected.
+
+        Returns:
+            bool: True when the record was written, False when part_id
+            resolves to no dataset. Never raises.
+        """
+        part_state = self._get_or_create_part_state(part_id)
+        if part_state is None:
+            return False
+        part_state.selected = selected
+        return True
+
+    def set_part_color_variable(self, part_id: int, variable_id: str, component: int | None) -> bool:
+        """
+        Set the variable a part is coloured by, and its component.
+
+        variable_id and component are set together, atomically, in this one
+        call, mirroring clear_part_color_variable's atomic clear.
+
+        Returns:
+            bool: True when the record was written, False when part_id
+            resolves to no dataset. Never raises.
+        """
+        part_state = self._get_or_create_part_state(part_id)
+        if part_state is None:
+            return False
+        part_state.spectrum_id = variable_id
+        part_state.spectrum_component = component
+        return True
+
+    def clear_part_color_variable(self, part_id: int) -> bool:
+        """
+        Clear the variable a part is coloured by.
+
+        Sets spectrum_id and spectrum_component to None together, in one
+        call — the compound class is only ever set or cleared atomically,
+        never field by field.
+
+        Returns:
+            bool: True when the record was written, False when part_id
+            resolves to no dataset. Never raises.
+        """
+        part_state = self._get_or_create_part_state(part_id)
+        if part_state is None:
+            return False
+        part_state.spectrum_id = None
+        part_state.spectrum_component = None
+        return True
+
+    def replace_part_states(self, dataset_states: Dict[int, RuntimeDatasetState]) -> None:
+        """
+        Replace the runtime state of registered datasets in bulk.
+
+        For each dataset ID present in both dataset_states and the
+        registry, that dataset's .state is replaced directly with the
+        supplied RuntimeDatasetState (already-runtime, id-keyed input).
+        Dataset IDs in dataset_states that are not present in the registry
+        are skipped silently; processing continues for the remaining
+        entries. Never raises.
+        """
+        for dataset_id, runtime_state in dataset_states.items():
+            dataset = self.datasets.get(dataset_id)
+            if dataset is None:
+                continue
+            dataset.state = runtime_state
+
     def _get_unique_dataset_name(self, name: str) -> str:
         """
         Rename the dataset by appending a suffix to ensure uniqueness.
diff --git a/tests/unit/vtk/datasets/test_visor_dataset_registry.py b/tests/unit/vtk/datasets/test_visor_dataset_registry.py
index d55ee2d6..15296e9e 100644
--- a/tests/unit/vtk/datasets/test_visor_dataset_registry.py
+++ b/tests/unit/vtk/datasets/test_visor_dataset_registry.py
@@ -3,6 +3,10 @@
 
 import pytest
 
+from ansys.visor.viewer.models.runtime.dataset.runtime_dataset_state import (
+    RuntimeDatasetState,
+    RuntimePartProperties,
+)
 from ansys.visor.viewer.vtk.datasets.visor_dataset_registry import VisorDatasetRegistry
 
 
@@ -23,6 +27,19 @@ def make_mock_dataset(name="ds", info_dict=None, parts=None, variables=None):
     return mock
 
 
+def make_part_dataset(dataset_id, part_ids, part_states=None):
+    """
+    Build a dataset stand-in with a real PartIndex.part_ids list and a real
+    RuntimeDatasetState (not MagicMock), so the per-part write path can
+    mutate and be read back through actual object identity.
+    """
+    dataset = MagicMock()
+    dataset.part_index = MagicMock()
+    dataset.part_index.part_ids = list(part_ids)
+    dataset.state = RuntimeDatasetState(id=dataset_id, part_states=part_states or {})
+    return dataset
+
+
 def test_count_returns_number_of_datasets(registry):
     """Verify that count returns the number of registered datasets."""
     assert registry.count == 0
@@ -180,3 +197,176 @@ def test_update_unit_matches_keeps_unit(registry):
 
     registry._update_unit(metadata)
     assert registry.unit == "m"
+
+
+# ================================================================== #
+# Per-part write path (Story 3.1, increment I1)
+# ================================================================== #
+
+def test_find_dataset_id_for_part_selects_between_multiple_datasets(registry):
+    """Verify the correct dataset id is returned when several datasets are registered."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10, 11])
+    ds_b = make_part_dataset(dataset_id=2, part_ids=[20, 21])
+    registry.datasets = {1: ds_a, 2: ds_b}
+
+    assert registry.find_dataset_id_for_part(20) == 2
+    assert registry.find_dataset_id_for_part(11) == 1
+
+
+def test_find_dataset_id_for_part_not_found_returns_none(registry):
+    """Verify an unknown part_id resolves to no dataset."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10, 11])
+    registry.datasets = {1: ds_a}
+
+    assert registry.find_dataset_id_for_part(999999) is None
+
+
+def test_get_part_state_returns_existing_record(registry):
+    """Verify get_part_state returns the recorded state for a known part."""
+    existing = RuntimePartProperties(id=10, opacity=0.7)
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={10: existing})
+    registry.datasets = {1: ds_a}
+
+    result = registry.get_part_state(10)
+    assert result is existing
+    assert result.opacity == 0.7
+
+
+def test_get_part_state_known_dataset_missing_part_returns_none(registry):
+    """Verify get_part_state does not upsert: a part with no record returns None."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10])
+    registry.datasets = {1: ds_a}
+
+    assert registry.get_part_state(10) is None
+    assert ds_a.state.part_states == {}
+
+
+def test_get_part_state_unknown_part_id_returns_none(registry):
+    """Verify get_part_state returns None, without raising, for an unknown part_id."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10])
+    registry.datasets = {1: ds_a}
+
+    assert registry.get_part_state(999999) is None
+
+
+def test_set_part_visibility_mutates_record_and_rejects_unknown_part(registry):
+    """Verify set_part_visibility writes True/False, and False + no raise for unknown part_id."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={10: RuntimePartProperties(id=10)})
+    registry.datasets = {1: ds_a}
+
+    assert registry.set_part_visibility(10, False) is True
+    assert registry.get_part_state(10).visible is False
+
+    assert registry.set_part_visibility(999999, True) is False
+
+
+def test_set_part_opacity_mutates_record_and_rejects_unknown_part(registry):
+    """Verify set_part_opacity writes the value, and False + no raise for unknown part_id."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={10: RuntimePartProperties(id=10)})
+    registry.datasets = {1: ds_a}
+
+    assert registry.set_part_opacity(10, 0.4) is True
+    assert registry.get_part_state(10).opacity == 0.4
+
+    assert registry.set_part_opacity(999999, 0.4) is False
+
+
+def test_set_part_diffuse_color_mutates_and_clears(registry):
+    """Verify set_part_diffuse_color writes an RGB list, clears with None, and rejects unknown parts."""
+    ds_a = make_part_dataset(
+        dataset_id=1, part_ids=[10],
+        part_states={10: RuntimePartProperties(id=10, diffuse_rgb=[1.0, 0.0, 0.0])},
+    )
+    registry.datasets = {1: ds_a}
+
+    assert registry.set_part_diffuse_color(10, [0.0, 1.0, 0.0]) is True
+    assert registry.get_part_state(10).diffuse_rgb == [0.0, 1.0, 0.0]
+
+    assert registry.set_part_diffuse_color(10, None) is True
+    assert registry.get_part_state(10).diffuse_rgb is None
+
+    assert registry.set_part_diffuse_color(999999, [1.0, 1.0, 1.0]) is False
+
+
+def test_set_part_selected_mutates_record_and_rejects_unknown_part(registry):
+    """Verify set_part_selected writes the value, and False + no raise for unknown part_id."""
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={10: RuntimePartProperties(id=10)})
+    registry.datasets = {1: ds_a}
+
+    assert registry.set_part_selected(10, True) is True
+    assert registry.get_part_state(10).selected is True
+
+    assert registry.set_part_selected(999999, True) is False
+
+
+def test_set_part_color_variable_sets_id_and_component_together(registry):
+    """Verify set_part_color_variable sets spectrum_id and spectrum_component in one call."""
+    seed = RuntimePartProperties(id=10)
+    assert seed.spectrum_id is None
+    assert seed.spectrum_component is None
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={10: seed})
+    registry.datasets = {1: ds_a}
+
+    assert registry.set_part_color_variable(10, "POINT::pressure::1", 2) is True
+
+    result = registry.get_part_state(10)
+    assert result.spectrum_id == "POINT::pressure::1"
+    assert result.spectrum_component == 2
+
+    assert registry.set_part_color_variable(999999, "POINT::x::1", 0) is False
+
+
+def test_clear_part_color_variable_clears_id_and_component_together(registry):
+    """Verify clear_part_color_variable clears spectrum_id and spectrum_component in one call."""
+    seed = RuntimePartProperties(id=10, spectrum_id="POINT::pressure::1", spectrum_component=2)
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={10: seed})
+    registry.datasets = {1: ds_a}
+
+    assert registry.clear_part_color_variable(10) is True
+
+    result = registry.get_part_state(10)
+    assert result.spectrum_id is None
+    assert result.spectrum_component is None
+
+    assert registry.clear_part_color_variable(999999) is False
+
+
+def test_setter_upserts_part_state_when_part_id_known_but_absent_from_part_states(registry):
+    """
+    Verify the upsert path: a part_id present in PartIndex.part_ids but absent
+    from part_states gets a RuntimePartProperties(id=part_id) created on first
+    write, rather than silently no-op-ing.
+    """
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10], part_states={})
+    registry.datasets = {1: ds_a}
+    assert ds_a.state.part_states == {}
+
+    assert registry.set_part_opacity(10, 0.6) is True
+
+    created = ds_a.state.part_states.get(10)
+    assert created is not None
+    assert isinstance(created, RuntimePartProperties)
+    assert created.id == 10
+    assert created.opacity == 0.6
+
+
+def test_replace_part_states_replaces_known_and_skips_unknown_without_aborting(registry):
+    """
+    Verify replace_part_states replaces the state of a known dataset id and
+    silently skips an unknown dataset id in the same call, without aborting
+    partway (the known replacement still lands).
+    """
+    ds_a = make_part_dataset(dataset_id=1, part_ids=[10])
+    original_state = ds_a.state
+    registry.datasets = {1: ds_a}
+
+    new_state_for_known = RuntimeDatasetState(id=1, part_states={10: RuntimePartProperties(id=10, opacity=0.9)})
+    new_state_for_unknown = RuntimeDatasetState(id=999, part_states={})
+
+    registry.replace_part_states({1: new_state_for_known, 999: new_state_for_unknown})
+
+    assert ds_a.state is new_state_for_known
+    assert ds_a.state is not original_state
+    assert 999 not in registry.datasets
+
+

From ac71d50afe0ec18df6e323b1d079a49cf318e00b Mon Sep 17 00:00:00 2001
From: Laura Kasian <lkasian@synopsys.com>
Date: Fri, 28 Aug 2026 12:44:15 -0700
Subject: [PATCH 2/8] remove story/increment reference in comment

---
 tests/unit/vtk/datasets/test_visor_dataset_registry.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/unit/vtk/datasets/test_visor_dataset_registry.py b/tests/unit/vtk/datasets/test_visor_dataset_registry.py
index 15296e9e..19047df9 100644
--- a/tests/unit/vtk/datasets/test_visor_dataset_registry.py
+++ b/tests/unit/vtk/datasets/test_visor_dataset_registry.py
@@ -200,7 +200,7 @@ def test_update_unit_matches_keeps_unit(registry):
 
 
 # ================================================================== #
-# Per-part write path (Story 3.1, increment I1)
+# Per-part write path
 # ================================================================== #
 
 def test_find_dataset_id_for_part_selects_between_multiple_datasets(registry):

From ee0b843048017803824b01dd20354cff01e7082d Mon Sep 17 00:00:00 2001
From: pyansys-ci-bot <92810346+pyansys-ci-bot@users.noreply.github.com>
Date: Fri, 28 Aug 2026 19:46:24 +0000
Subject: [PATCH 3/8] chore: adding changelog file 50.added.md
 [dependabot-skip]

---
 doc/changelog.d/50.added.md | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 doc/changelog.d/50.added.md

diff --git a/doc/changelog.d/50.added.md b/doc/changelog.d/50.added.md
new file mode 100644
index 00000000..947c8ced
--- /dev/null
+++ b/doc/changelog.d/50.added.md
@@ -0,0 +1 @@
+Remote rendering 3.1 - add per-part write path to the dataset registry

From ff688aa122dd96fe2b38e8ea8dc8d951e7cc4457 Mon Sep 17 00:00:00 2001
From: pyansys-ci-bot <92810346+pyansys-ci-bot@users.noreply.github.com>
Date: Fri, 28 Aug 2026 20:02:36 +0000
Subject: [PATCH 4/8] chore: adding changelog file 50.added.md
 [dependabot-skip]

---
 doc/changelog.d/50.added.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/changelog.d/50.added.md b/doc/changelog.d/50.added.md
index 947c8ced..86f36f04 100644
--- a/doc/changelog.d/50.added.md
+++ b/doc/changelog.d/50.added.md
@@ -1 +1 @@
-Remote rendering 3.1 - add per-part write path to the dataset registry
+Remote rendering 3.1a - add per-part write path to the dataset registry

From ccc2f0f78fa4df1ad843f126276b25c4185925a7 Mon Sep 17 00:00:00 2001
From: Laura Kasian <lkasian@synopsys.com>
Date: Fri, 28 Aug 2026 12:18:46 -0700
Subject: [PATCH 5/8] implement visibility, opacity and diffuse-color applies
 on the local renderer

---
 .../visor/viewer/renderer/local_renderer.py   |  39 +++-
 tests/unit/renderer/test_local_renderer.py    | 167 ++++++++++++++++--
 2 files changed, 191 insertions(+), 15 deletions(-)

diff --git a/src/ansys/visor/viewer/renderer/local_renderer.py b/src/ansys/visor/viewer/renderer/local_renderer.py
index 4d07003a..b334fa3d 100644
--- a/src/ansys/visor/viewer/renderer/local_renderer.py
+++ b/src/ansys/visor/viewer/renderer/local_renderer.py
@@ -158,15 +158,48 @@ def deregister_all(self) -> None:
     # ------------------------------------------------------------------
 
     def apply_visibility(self, node_id: int, visible: bool) -> None:
-        """No-op in Story 1.2. Phase 3 populates."""
+        """See :meth:`IRenderer.apply_visibility`.
+
+        Mutates the actor itself, not its property.  An unknown *node_id*
+        is a logged no-op, never a raise.
+        """
+        pipe = self._pipelines.get(node_id)
+        if pipe is None:
+            logger.debug(
+                "apply_visibility: no pipeline for node %s; skipping.", node_id
+            )
+            return
+        pipe.actor.SetVisibility(1 if visible else 0)
 
     def apply_opacity(self, node_id: int, opacity: float) -> None:
-        """No-op in Story 1.2. Phase 3 populates."""
+        """See :meth:`IRenderer.apply_opacity`.
+
+        Mutates the actor's property.  An unknown *node_id* is a logged
+        no-op, never a raise.
+        """
+        pipe = self._pipelines.get(node_id)
+        if pipe is None:
+            logger.debug(
+                "apply_opacity: no pipeline for node %s; skipping.", node_id
+            )
+            return
+        pipe.actor.GetProperty().SetOpacity(opacity)
 
     def apply_diffuse_color(
         self, node_id: int, r: float, g: float, b: float
     ) -> None:
-        """No-op in Story 1.2. Phase 3 populates."""
+        """See :meth:`IRenderer.apply_diffuse_color`.
+
+        Mutates the actor property's diffuse colour only.  An unknown
+        *node_id* is a logged no-op, never a raise.
+        """
+        pipe = self._pipelines.get(node_id)
+        if pipe is None:
+            logger.debug(
+                "apply_diffuse_color: no pipeline for node %s; skipping.", node_id
+            )
+            return
+        pipe.actor.GetProperty().SetDiffuseColor(r, g, b)
 
     def apply_edge_visibility(self, node_id: int, edge_visible: bool) -> None:
         """No-op in Story 1.2. Phase 3 populates."""
diff --git a/tests/unit/renderer/test_local_renderer.py b/tests/unit/renderer/test_local_renderer.py
index c0bd33ae..038959ee 100644
--- a/tests/unit/renderer/test_local_renderer.py
+++ b/tests/unit/renderer/test_local_renderer.py
@@ -6,8 +6,9 @@
 1.  Node lifecycle  -- register_node / deregister_node (the non-trivial seam).
 2.  Interface conformance -- NullRenderer and VisorLocalRenderer both satisfy
     IRenderer's abstract contract.
-3.  Per-part visual mutations -- one focused test per property;
-    tests assert they accept their arguments and return None.
+3.  Per-part visual mutations -- visibility, opacity and diffuse colour
+    mutate the resolved pipeline's VTK objects; the remaining methods are
+    still no-ops and are asserted to accept their arguments and return None.
 4.  Camera round-trip -- reset_camera, sync_camera / get_camera_state.
 5.  Render / flush delegation.
 6.  pick_geometry -- vertex, edge, face modes.
@@ -18,6 +19,7 @@
 from unittest.mock import MagicMock, patch
 
 import pytest
+from vtkmodules.vtkRenderingCore import vtkActor
 
 from ansys.visor.viewer.renderer.base import IRenderer
 from ansys.visor.viewer.renderer.local_renderer import VisorLocalRenderer
@@ -92,6 +94,20 @@ def GetNextActor(self): # noqa: N802
         return a
 
 
+class _DummyPipeline:
+    """VtkNodePipeline stand-in holding a *real* vtkActor.
+
+    The actor is real so that a test can read the mutated value back off
+    the VTK object (``GetVisibility``, ``GetProperty().GetOpacity()``,
+    ``GetProperty().GetDiffuseColor()``) rather than merely recording that
+    some call was made -- a MagicMock would pass even if the production
+    code mutated the wrong object or the wrong field.
+    """
+
+    def __init__(self):
+        self.actor = vtkActor()
+
+
 # ---------------------------------------------------------------------------
 # Fixture: VisorLocalRenderer with all VTK infrastructure mocked
 # ---------------------------------------------------------------------------
@@ -336,16 +352,7 @@ def test_deregister_all_empties_registry_and_detaches_all_actors(self, renderer)
 # ===========================================================================
 
 class TestPerPartMutations:
-    """Each method accepts its contract arguments and returns None without raising."""
-
-    def test_apply_visibility(self, renderer):
-        assert renderer.apply_visibility(1, True) is None
-
-    def test_apply_opacity(self, renderer):
-        assert renderer.apply_opacity(1, 0.5) is None
-
-    def test_apply_diffuse_color(self, renderer):
-        assert renderer.apply_diffuse_color(1, 1.0, 0.0, 0.0) is None
+    """The methods still un-implemented accept their arguments and return None."""
 
     def test_apply_edge_visibility(self, renderer):
         assert renderer.apply_edge_visibility(1, False) is None
@@ -369,6 +376,142 @@ def test_refresh_color_variable_range(self, renderer):
         )
 
 
+# ===========================================================================
+# 3b.  Inline apply bodies: visibility, opacity, diffuse colour
+#
+#      Each mutation is read back off a real vtkActor, and each miss branch
+#      (unknown node id) is asserted separately.
+# ===========================================================================
+
+class TestInlineApplyBodies:
+
+    # ------------------------------------------------------------------
+    # visibility -- mutates the actor itself
+    # ------------------------------------------------------------------
+
+    def test_apply_visibility_shows_actor(self, renderer):
+        """apply_visibility(True) leaves the actor's visibility flag set."""
+        pipe = _DummyPipeline()
+        pipe.actor.SetVisibility(0)
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_visibility(4, True)
+
+        assert pipe.actor.GetVisibility() == 1
+
+    def test_apply_visibility_hides_actor(self, renderer):
+        """apply_visibility(False) leaves the actor's visibility flag clear."""
+        pipe = _DummyPipeline()
+        pipe.actor.SetVisibility(1)
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_visibility(4, False)
+
+        assert pipe.actor.GetVisibility() == 0
+
+    def test_apply_visibility_unknown_node_id_is_logged_no_op(self, renderer):
+        """An unregistered node id logs at debug, does not raise, mutates nothing."""
+        pipe = _DummyPipeline()
+        pipe.actor.SetVisibility(1)
+        renderer._pipelines[4] = pipe
+
+        with patch(
+            "ansys.visor.viewer.renderer.local_renderer.logger"
+        ) as mock_logger:
+            renderer.apply_visibility(9999, False)  # must not raise
+
+        mock_logger.debug.assert_called_once()
+        assert pipe.actor.GetVisibility() == 1
+
+    # ------------------------------------------------------------------
+    # opacity -- mutates the actor's property
+    # ------------------------------------------------------------------
+
+    def test_apply_opacity_sets_property_opacity(self, renderer):
+        """apply_opacity writes the requested value onto the actor property."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_opacity(4, 0.25)
+
+        assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.25)
+
+    def test_apply_opacity_does_not_touch_visibility_or_diffuse_color(self, renderer):
+        """Opacity lands on the property's opacity field and nothing else."""
+        pipe = _DummyPipeline()
+        pipe.actor.SetVisibility(0)
+        pipe.actor.GetProperty().SetDiffuseColor(0.25, 0.5, 0.75)
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_opacity(4, 0.25)
+
+        assert pipe.actor.GetVisibility() == 0
+        assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
+            (0.25, 0.5, 0.75)
+        )
+
+    def test_apply_opacity_unknown_node_id_is_logged_no_op(self, renderer):
+        """An unregistered node id logs at debug, does not raise, mutates nothing."""
+        pipe = _DummyPipeline()
+        pipe.actor.GetProperty().SetOpacity(0.75)
+        renderer._pipelines[4] = pipe
+
+        with patch(
+            "ansys.visor.viewer.renderer.local_renderer.logger"
+        ) as mock_logger:
+            renderer.apply_opacity(9999, 0.25)  # must not raise
+
+        mock_logger.debug.assert_called_once()
+        assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.75)
+
+    # ------------------------------------------------------------------
+    # diffuse colour -- mutates the actor property's DiffuseColor
+    # ------------------------------------------------------------------
+
+    def test_apply_diffuse_color_sets_property_diffuse_color(self, renderer):
+        """apply_diffuse_color writes r, g, b onto the property's diffuse colour."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_diffuse_color(4, 1.0, 0.0, 0.0)
+
+        assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
+            (1.0, 0.0, 0.0)
+        )
+
+    def test_apply_diffuse_color_does_not_touch_ambient_color_or_opacity(
+        self, renderer
+    ):
+        """SetDiffuseColor, not SetColor or SetAmbientColor, and opacity is left alone."""
+        pipe = _DummyPipeline()
+        pipe.actor.GetProperty().SetAmbientColor(0.25, 0.5, 0.75)
+        pipe.actor.GetProperty().SetOpacity(0.75)
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_diffuse_color(4, 1.0, 0.0, 0.0)
+
+        assert pipe.actor.GetProperty().GetAmbientColor() == pytest.approx(
+            (0.25, 0.5, 0.75)
+        )
+        assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.75)
+
+    def test_apply_diffuse_color_unknown_node_id_is_logged_no_op(self, renderer):
+        """An unregistered node id logs at debug, does not raise, mutates nothing."""
+        pipe = _DummyPipeline()
+        pipe.actor.GetProperty().SetDiffuseColor(0.25, 0.5, 0.75)
+        renderer._pipelines[4] = pipe
+
+        with patch(
+            "ansys.visor.viewer.renderer.local_renderer.logger"
+        ) as mock_logger:
+            renderer.apply_diffuse_color(9999, 1.0, 0.0, 0.0)  # must not raise
+
+        mock_logger.debug.assert_called_once()
+        assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
+            (0.25, 0.5, 0.75)
+        )
+
+
 # ===========================================================================
 # 4.  Camera
 # ===========================================================================

From c62294fcc98389e9adeab99d62f74ee61326658b Mon Sep 17 00:00:00 2001
From: Laura Kasian <lkasian@synopsys.com>
Date: Fri, 28 Aug 2026 12:19:37 -0700
Subject: [PATCH 6/8] move selection and color-variable applies onto
 VtkNodePipeline

---
 .../visor/viewer/renderer/local_renderer.py   |  49 +++-
 src/ansys/visor/viewer/vtk/node_pipeline.py   |  97 ++++++++
 tests/unit/renderer/test_local_renderer.py    | 127 ++++++++--
 tests/unit/vtk/test_node_pipeline.py          | 226 +++++++++++++++++-
 4 files changed, 481 insertions(+), 18 deletions(-)

diff --git a/src/ansys/visor/viewer/renderer/local_renderer.py b/src/ansys/visor/viewer/renderer/local_renderer.py
index b334fa3d..47913992 100644
--- a/src/ansys/visor/viewer/renderer/local_renderer.py
+++ b/src/ansys/visor/viewer/renderer/local_renderer.py
@@ -207,7 +207,21 @@ def apply_edge_visibility(self, node_id: int, edge_visible: bool) -> None:
     def apply_selected(
         self, node_id: int, selected: bool, diffuse_rgb: list
     ) -> None:
-        """No-op in Story 1.2. Phase 3 populates."""
+        """See :meth:`IRenderer.apply_selected`.
+
+        Resolves the pipeline and delegates to
+        :meth:`VtkNodePipeline.set_selected`.  *diffuse_rgb* is passed
+        through as given; supplying a default when the part has no stored
+        colour is the coordinator's job, not the renderer's.  An unknown
+        *node_id* is a logged no-op, never a raise.
+        """
+        pipe = self._pipelines.get(node_id)
+        if pipe is None:
+            logger.debug(
+                "apply_selected: no pipeline for node %s; skipping.", node_id
+            )
+            return
+        pipe.set_selected(selected, diffuse_rgb)
 
     def apply_color_variable(
         self,
@@ -219,10 +233,39 @@ def apply_color_variable(
         min_val: float,
         max_val: float,
     ) -> None:
-        """No-op in Story 1.2. Phase 3 populates."""
+        """See :meth:`IRenderer.apply_color_variable`.
+
+        Resolves the pipeline and delegates to
+        :meth:`VtkNodePipeline.set_color_variable`.  *array_type* must
+        already be a :class:`VisorVtkVariableType`; it is parsed at the
+        trigger boundary, never here, and the pipeline compares it by
+        identity, so any other value is a logged no-op there.
+        *spectrum_id* is not forwarded -- it is stored opaquely by the
+        registry and is not needed to configure the mapper.  An unknown
+        *node_id* is a logged no-op, never a raise.
+        """
+        pipe = self._pipelines.get(node_id)
+        if pipe is None:
+            logger.debug(
+                "apply_color_variable: no pipeline for node %s; skipping.", node_id
+            )
+            return
+        pipe.set_color_variable(array_type, array_name, component, min_val, max_val)
 
     def clear_color_variable(self, node_id: int) -> None:
-        """No-op in Story 1.2. Phase 3 populates."""
+        """See :meth:`IRenderer.clear_color_variable`.
+
+        Resolves the pipeline and delegates to
+        :meth:`VtkNodePipeline.clear_color_variable`.  An unknown
+        *node_id* is a logged no-op, never a raise.
+        """
+        pipe = self._pipelines.get(node_id)
+        if pipe is None:
+            logger.debug(
+                "clear_color_variable: no pipeline for node %s; skipping.", node_id
+            )
+            return
+        pipe.clear_color_variable()
 
     def refresh_color_variable_range(
         self,
diff --git a/src/ansys/visor/viewer/vtk/node_pipeline.py b/src/ansys/visor/viewer/vtk/node_pipeline.py
index 7adeb5ad..1e97dcc1 100644
--- a/src/ansys/visor/viewer/vtk/node_pipeline.py
+++ b/src/ansys/visor/viewer/vtk/node_pipeline.py
@@ -27,6 +27,7 @@
 from vtkmodules.vtkRenderingCore import vtkActor, vtkPolyDataMapper
 
 from ansys.visor.viewer.core.visor_colors import VisorColors
+from ansys.visor.viewer.core.visor_enums import VisorVtkVariableType
 from ansys.visor.viewer.core.visor_logging import VisorDefaultLogger
 
 logger = VisorDefaultLogger(__name__)
@@ -105,6 +106,102 @@ def update_input(
             algorithm = algorithm_filter(algorithm)
         self.mapper.SetInputConnection(algorithm.GetOutputPort())
 
+    # ------------------------------------------------------------------
+    # Per-part visual mutations
+    #
+    # These bodies live here rather than on the renderer because each is
+    # more than one VTK call, and the colour-variable body additionally
+    # reads a pipeline-internal object (``base_algorithm``).  Identity
+    # resolution (node id -> pipeline) and the miss branch stay on the
+    # renderer, which is the only holder of the id -> pipeline map.
+    # ------------------------------------------------------------------
+
+    def set_selected(self, selected: bool, diffuse_rgb: list[float]) -> None:
+        """Apply or remove the selection highlight on this part.
+
+        Parameters
+        ----------
+        selected:
+            Target state.  Absolute, never a toggle.
+        diffuse_rgb:
+            The part's diffuse colour, re-applied unconditionally on both
+            branches -- selection changes the ambient/diffuse lighting
+            terms, it does not replace the part's colour.
+        """
+        prop = self.actor.GetProperty()
+        if selected:
+            prop.SetAmbientColor(0 / 255, 62 / 255, 111 / 255)
+            prop.SetDiffuse(0.5)
+            prop.SetAmbient(0.5)
+        else:
+            prop.SetDiffuse(1.0)
+            prop.SetAmbient(0.0)
+        prop.SetDiffuseColor(*diffuse_rgb)
+
+    def set_color_variable(
+        self,
+        association: VisorVtkVariableType,
+        array_name: str,
+        component: int,
+        min_val: float,
+        max_val: float,
+    ) -> None:
+        """Colour this part by a scalar array, over an explicit range.
+
+        Configures the mapper only.  No lookup table is authored here: the
+        table belongs to a later story, and until then a reference resolves
+        against the client-held default table.
+
+        ``association`` is compared by identity against
+        :class:`VisorVtkVariableType`; it is never parsed, upper-cased or
+        string-compared.  A value that is neither member, and an array name
+        that does not exist on the input, are both logged no-ops that
+        mutate nothing.
+        """
+        in_data = self.base_algorithm.GetInput()
+        if association is VisorVtkVariableType.POINT:
+            field = in_data.GetPointData()
+        elif association is VisorVtkVariableType.CELL:
+            field = in_data.GetCellData()
+        else:
+            logger.warning(
+                "set_color_variable: association %r is not a VisorVtkVariableType; "
+                "skipping.",
+                association,
+            )
+            return
+
+        if field.GetArray(array_name) is None:
+            logger.warning(
+                "set_color_variable: array %r not found for association %s; skipping.",
+                array_name,
+                association,
+            )
+            return
+
+        mapper = self.mapper
+        if association is VisorVtkVariableType.POINT:
+            mapper.SetScalarModeToUsePointFieldData()
+        else:
+            mapper.SetScalarModeToUseCellFieldData()
+        mapper.SelectColorArray(array_name)
+        mapper.SetArrayComponent(component)
+        mapper.SetScalarRange(min_val, max_val)
+        mapper.SetColorModeToMapScalars()
+        mapper.SetScalarVisibility(True)
+        # Makes the mapper honour the range set above rather than the
+        # lookup table's own range.
+        mapper.SetUseLookupTableScalarRange(0)
+
+    def clear_color_variable(self) -> None:
+        """Stop colouring this part by a scalar array.
+
+        One call.  Does not touch a lookup table and does not restore a
+        diffuse colour -- the part's colour is whatever was last applied
+        to it.
+        """
+        self.mapper.SetScalarVisibility(False)
+
     # ------------------------------------------------------------------
     # Private helpers
     # ------------------------------------------------------------------
diff --git a/tests/unit/renderer/test_local_renderer.py b/tests/unit/renderer/test_local_renderer.py
index 038959ee..8fc9bfb2 100644
--- a/tests/unit/renderer/test_local_renderer.py
+++ b/tests/unit/renderer/test_local_renderer.py
@@ -7,8 +7,10 @@
 2.  Interface conformance -- NullRenderer and VisorLocalRenderer both satisfy
     IRenderer's abstract contract.
 3.  Per-part visual mutations -- visibility, opacity and diffuse colour
-    mutate the resolved pipeline's VTK objects; the remaining methods are
-    still no-ops and are asserted to accept their arguments and return None.
+    mutate the resolved pipeline's VTK objects directly; selection and
+    colour variable resolve the pipeline and delegate to VtkNodePipeline
+    (their VTK effects are asserted in tests/unit/vtk/test_node_pipeline.py);
+    edge visibility and the colour-variable range refresh stay no-ops.
 4.  Camera round-trip -- reset_camera, sync_camera / get_camera_state.
 5.  Render / flush delegation.
 6.  pick_geometry -- vertex, edge, face modes.
@@ -21,6 +23,7 @@
 import pytest
 from vtkmodules.vtkRenderingCore import vtkActor
 
+from ansys.visor.viewer.core.visor_enums import VisorVtkVariableType
 from ansys.visor.viewer.renderer.base import IRenderer
 from ansys.visor.viewer.renderer.local_renderer import VisorLocalRenderer
 from ansys.visor.viewer.renderer.null_renderer import NullRenderer
@@ -102,10 +105,18 @@ class _DummyPipeline:
     ``GetProperty().GetDiffuseColor()``) rather than merely recording that
     some call was made -- a MagicMock would pass even if the production
     code mutated the wrong object or the wrong field.
+
+    The three delegated mutations are MagicMocks, because from this module
+    the behaviour under test is *that the renderer resolved and delegated*.
+    Their VTK effects are asserted against real objects in
+    ``tests/unit/vtk/test_node_pipeline.py``.
     """
 
     def __init__(self):
         self.actor = vtkActor()
+        self.set_selected = MagicMock(name="set_selected")
+        self.set_color_variable = MagicMock(name="set_color_variable")
+        self.clear_color_variable = MagicMock(name="clear_color_variable")
 
 
 # ---------------------------------------------------------------------------
@@ -352,22 +363,15 @@ def test_deregister_all_empties_registry_and_detaches_all_actors(self, renderer)
 # ===========================================================================
 
 class TestPerPartMutations:
-    """The methods still un-implemented accept their arguments and return None."""
+    """The two permanently un-implemented methods accept their arguments.
+
+    Both stay no-ops beyond this story: edge visibility is a global display
+    toggle, and the colour-variable range is not held per part.
+    """
 
     def test_apply_edge_visibility(self, renderer):
         assert renderer.apply_edge_visibility(1, False) is None
 
-    def test_apply_selected(self, renderer):
-        assert renderer.apply_selected(1, True, [1.0, 0.0, 0.0]) is None
-
-    def test_apply_color_variable(self, renderer):
-        assert (
-            renderer.apply_color_variable(1, "sp-1", "POINT", "pressure", -1, 0.0, 1.0)
-            is None
-        )
-
-    def test_clear_color_variable(self, renderer):
-        assert renderer.clear_color_variable(1) is None
 
     def test_refresh_color_variable_range(self, renderer):
         assert (
@@ -512,6 +516,101 @@ def test_apply_diffuse_color_unknown_node_id_is_logged_no_op(self, renderer):
         )
 
 
+# ===========================================================================
+# 3c.  Delegated apply bodies: selection, colour variable
+#
+#      The VTK effects of these live on VtkNodePipeline and are asserted in
+#      tests/unit/vtk/test_node_pipeline.py.  What is asserted here is that
+#      the renderer resolved the pipeline and delegated with the arguments
+#      it was given, and that an unknown node id is a logged no-op.
+# ===========================================================================
+
+class TestDelegatedApplyBodies:
+
+    # ------------------------------------------------------------------
+    # apply_selected
+    # ------------------------------------------------------------------
+
+    def test_apply_selected_delegates_to_pipeline(self, renderer):
+        """Selection state and the given colour are passed straight through."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_selected(4, True, [1.0, 0.0, 0.0])
+
+        pipe.set_selected.assert_called_once_with(True, [1.0, 0.0, 0.0])
+
+    def test_apply_selected_unknown_node_id_is_logged_no_op(self, renderer):
+        """An unregistered node id logs at debug, does not raise, delegates nothing."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        with patch(
+            "ansys.visor.viewer.renderer.local_renderer.logger"
+        ) as mock_logger:
+            renderer.apply_selected(9999, True, [1.0, 0.0, 0.0])  # must not raise
+
+        mock_logger.debug.assert_called_once()
+        pipe.set_selected.assert_not_called()
+
+    # ------------------------------------------------------------------
+    # apply_color_variable
+    # ------------------------------------------------------------------
+
+    def test_apply_color_variable_delegates_with_given_arguments(self, renderer):
+        """The association is forwarded unchanged; spectrum_id is not forwarded."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        renderer.apply_color_variable(
+            4, "sp-1", VisorVtkVariableType.POINT, "pressure", 1, 0.0, 7.5
+        )
+
+        pipe.set_color_variable.assert_called_once_with(
+            VisorVtkVariableType.POINT, "pressure", 1, 0.0, 7.5
+        )
+
+    def test_apply_color_variable_unknown_node_id_is_logged_no_op(self, renderer):
+        """An unregistered node id logs at debug, does not raise, delegates nothing."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        with patch(
+            "ansys.visor.viewer.renderer.local_renderer.logger"
+        ) as mock_logger:
+            renderer.apply_color_variable(
+                9999, "sp-1", VisorVtkVariableType.POINT, "pressure", 1, 0.0, 7.5
+            )  # must not raise
+
+        mock_logger.debug.assert_called_once()
+        pipe.set_color_variable.assert_not_called()
+
+    # ------------------------------------------------------------------
+    # clear_color_variable
+    # ------------------------------------------------------------------
+
+    def test_clear_color_variable_delegates_to_pipeline(self, renderer):
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        renderer.clear_color_variable(4)
+
+        pipe.clear_color_variable.assert_called_once_with()
+
+    def test_clear_color_variable_unknown_node_id_is_logged_no_op(self, renderer):
+        """An unregistered node id logs at debug, does not raise, delegates nothing."""
+        pipe = _DummyPipeline()
+        renderer._pipelines[4] = pipe
+
+        with patch(
+            "ansys.visor.viewer.renderer.local_renderer.logger"
+        ) as mock_logger:
+            renderer.clear_color_variable(9999)  # must not raise
+
+        mock_logger.debug.assert_called_once()
+        pipe.clear_color_variable.assert_not_called()
+
+
 # ===========================================================================
 # 4.  Camera
 # ===========================================================================
diff --git a/tests/unit/vtk/test_node_pipeline.py b/tests/unit/vtk/test_node_pipeline.py
index 8443ca7a..96115c51 100644
--- a/tests/unit/vtk/test_node_pipeline.py
+++ b/tests/unit/vtk/test_node_pipeline.py
@@ -1,8 +1,9 @@
 """Unit tests for VtkNodePipeline."""
 
-from unittest.mock import MagicMock
+from unittest.mock import MagicMock, patch
 
 import pytest
+from vtkmodules.vtkCommonCore import vtkFloatArray
 from vtkmodules.vtkCommonDataModel import vtkPlane, vtkPolyData, vtkUnstructuredGrid
 from vtkmodules.vtkFiltersCore import vtkAppendPolyData
 from vtkmodules.vtkFiltersGeometry import vtkGeometryFilter
@@ -10,6 +11,7 @@
 from vtkmodules.vtkRenderingCore import vtkActor, vtkPolyDataMapper
 
 from ansys.visor.viewer.core.visor_colors import VisorColors
+from ansys.visor.viewer.core.visor_enums import VisorVtkVariableType
 from ansys.visor.viewer.vtk.node_pipeline import VtkNodePipeline
 
 
@@ -26,6 +28,38 @@ def unstructured_dataset() -> vtkUnstructuredGrid:
     return vtkUnstructuredGrid()
 
 
+@pytest.fixture
+def array_dataset() -> vtkPolyData:
+    """Sphere output carrying one named point array and one named cell array.
+
+    Each array is sized from the dataset's own counts -- the point array to
+    ``GetNumberOfPoints()`` and the cell array to ``GetNumberOfCells()`` -- so
+    the arrays are valid for the association they are attached to.  For the
+    default vtkSphereSource that is 50 points and 96 cells.
+    """
+    src = vtkSphereSource()
+    src.Update()
+    dataset = src.GetOutput()
+
+    pressure = vtkFloatArray()
+    pressure.SetName("pressure")
+    pressure.SetNumberOfComponents(1)
+    pressure.SetNumberOfTuples(dataset.GetNumberOfPoints())
+    for i in range(dataset.GetNumberOfPoints()):
+        pressure.SetTuple1(i, float(i))
+    dataset.GetPointData().AddArray(pressure)
+
+    temperature = vtkFloatArray()
+    temperature.SetName("temperature")
+    temperature.SetNumberOfComponents(1)
+    temperature.SetNumberOfTuples(dataset.GetNumberOfCells())
+    for i in range(dataset.GetNumberOfCells()):
+        temperature.SetTuple1(i, float(i))
+    dataset.GetCellData().AddArray(temperature)
+
+    return dataset
+
+
 # ---------------------------------------------------------------------------
 # from_dataset
 # ---------------------------------------------------------------------------
@@ -132,3 +166,193 @@ def algorithm_filter(base):
     assert pipe.mapper.GetInputConnection(0, 0).GetProducer() is wrapper
 
 
+# ---------------------------------------------------------------------------
+# set_selected
+#
+# The selection highlight colour is ambient RGB 0, 62, 111 out of 255.  The
+# expected values below are written as decimal literals so that the test does
+# not restate the production expression.
+# ---------------------------------------------------------------------------
+
+SELECTION_AMBIENT_COLOR = (0.0, 0.24313725490196078, 0.43529411764705883)
+
+
+def test_set_selected_true_sets_selection_ambient_color_and_lighting(poly_dataset):
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+
+    pipe.set_selected(True, [0.1, 0.2, 0.3])
+
+    prop = pipe.actor.GetProperty()
+    assert prop.GetAmbientColor() == pytest.approx(SELECTION_AMBIENT_COLOR)
+    assert prop.GetDiffuse() == pytest.approx(0.5)
+    assert prop.GetAmbient() == pytest.approx(0.5)
+
+
+def test_set_selected_true_still_applies_the_given_diffuse_color(poly_dataset):
+    """Selecting changes the lighting terms; it does not replace the colour."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+
+    pipe.set_selected(True, [1.0, 0.0, 0.0])
+
+    assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx((1.0, 0.0, 0.0))
+
+
+def test_set_selected_false_restores_lighting_defaults(poly_dataset):
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+    pipe.set_selected(True, [1.0, 0.0, 0.0])
+
+    pipe.set_selected(False, [0.0, 1.0, 0.0])
+
+    prop = pipe.actor.GetProperty()
+    assert prop.GetDiffuse() == pytest.approx(1.0)
+    assert prop.GetAmbient() == pytest.approx(0.0)
+    assert prop.GetDiffuseColor() == pytest.approx((0.0, 1.0, 0.0))
+
+
+def test_set_selected_false_leaves_ambient_color_untouched(poly_dataset):
+    """Deselecting resets the ambient *term*, not the ambient colour."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+    # Seeded ambient colour: a distinctive value neither branch writes.
+    pipe.actor.GetProperty().SetAmbientColor(0.11, 0.22, 0.33)
+
+    pipe.set_selected(False, [0.0, 1.0, 0.0])
+
+    assert pipe.actor.GetProperty().GetAmbientColor() == pytest.approx(
+        (0.11, 0.22, 0.33)
+    )
+
+
+# ---------------------------------------------------------------------------
+# set_color_variable
+# ---------------------------------------------------------------------------
+
+def test_set_color_variable_point_uses_point_field_data_and_selects_array(
+    array_dataset,
+):
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+
+    pipe.set_color_variable(VisorVtkVariableType.POINT, "pressure", 0, 0.0, 7.5)
+
+    assert pipe.mapper.GetScalarModeAsString() == "UsePointFieldData"
+    assert pipe.mapper.GetArrayName() == "pressure"
+
+
+def test_set_color_variable_cell_uses_cell_field_data(array_dataset):
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+
+    pipe.set_color_variable(VisorVtkVariableType.CELL, "temperature", 0, 0.0, 7.5)
+
+    assert pipe.mapper.GetScalarModeAsString() == "UseCellFieldData"
+    assert pipe.mapper.GetArrayName() == "temperature"
+
+
+def test_set_color_variable_sets_the_array_component(array_dataset):
+    """Component selection lives on the mapper, not on a lookup table."""
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+
+    pipe.set_color_variable(VisorVtkVariableType.POINT, "pressure", 1, 0.0, 7.5)
+
+    assert pipe.mapper.GetArrayComponent() == 1
+
+
+def test_set_color_variable_sets_exact_scalar_range(array_dataset):
+    """The mapper honours the passed range, not a table's own range.
+
+    If SetUseLookupTableScalarRange(0) were omitted the mapper would defer to
+    the lookup table and the range read back would not be what was passed.
+    """
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+
+    pipe.set_color_variable(VisorVtkVariableType.POINT, "pressure", 0, 0.0, 7.5)
+
+    assert pipe.mapper.GetScalarRange() == pytest.approx((0.0, 7.5))
+    assert pipe.mapper.GetUseLookupTableScalarRange() == 0
+
+
+def test_set_color_variable_enables_scalar_visibility_and_map_scalars(array_dataset):
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+    # Seeded scalar visibility: OFF, so an enabling call is visible.
+    pipe.mapper.SetScalarVisibility(False)
+
+    pipe.set_color_variable(VisorVtkVariableType.POINT, "pressure", 0, 0.0, 7.5)
+
+    assert pipe.mapper.GetScalarVisibility() == 1
+    assert pipe.mapper.GetColorModeAsString() == "MapScalars"
+
+
+def test_set_color_variable_unknown_point_array_warns_and_mutates_nothing(
+    array_dataset,
+):
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+    # Seeded state: scalar visibility OFF and a sentinel array name.  If the
+    # body wrongly proceeded, both would change.
+    pipe.mapper.SetScalarVisibility(False)
+    pipe.mapper.SelectColorArray("seeded-sentinel-array")
+
+    with patch("ansys.visor.viewer.vtk.node_pipeline.logger") as mock_logger:
+        pipe.set_color_variable(VisorVtkVariableType.POINT, "no-such-array", 0, 0.0, 7.5)
+
+    mock_logger.warning.assert_called_once()
+    assert pipe.mapper.GetScalarVisibility() == 0
+    assert pipe.mapper.GetArrayName() == "seeded-sentinel-array"
+
+
+def test_set_color_variable_unknown_cell_array_warns_and_mutates_nothing(array_dataset):
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+    # Seeded state, as above.  "pressure" exists but only as a *point* array,
+    # so the cell-side lookup must miss.
+    pipe.mapper.SetScalarVisibility(False)
+    pipe.mapper.SelectColorArray("seeded-sentinel-array")
+
+    with patch("ansys.visor.viewer.vtk.node_pipeline.logger") as mock_logger:
+        pipe.set_color_variable(VisorVtkVariableType.CELL, "pressure", 0, 0.0, 7.5)
+
+    mock_logger.warning.assert_called_once()
+    assert pipe.mapper.GetScalarVisibility() == 0
+    assert pipe.mapper.GetArrayName() == "seeded-sentinel-array"
+
+
+def test_set_color_variable_non_enum_association_warns_and_mutates_nothing(
+    array_dataset,
+):
+    """A bare string is not a VisorVtkVariableType and must not pick a branch."""
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+    # Seeded state: scalar visibility OFF and a sentinel array name.
+    pipe.mapper.SetScalarVisibility(False)
+    pipe.mapper.SelectColorArray("seeded-sentinel-array")
+
+    with patch("ansys.visor.viewer.vtk.node_pipeline.logger") as mock_logger:
+        pipe.set_color_variable("POINT", "pressure", 0, 0.0, 7.5)
+
+    mock_logger.warning.assert_called_once()
+    assert pipe.mapper.GetScalarVisibility() == 0
+    assert pipe.mapper.GetArrayName() == "seeded-sentinel-array"
+
+
+# ---------------------------------------------------------------------------
+# clear_color_variable
+# ---------------------------------------------------------------------------
+
+def test_clear_color_variable_disables_scalar_visibility(array_dataset):
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+    pipe.set_color_variable(VisorVtkVariableType.POINT, "pressure", 0, 0.0, 7.5)
+    assert pipe.mapper.GetScalarVisibility() == 1
+
+    pipe.clear_color_variable()
+
+    assert pipe.mapper.GetScalarVisibility() == 0
+
+
+def test_clear_color_variable_leaves_diffuse_color_untouched(array_dataset):
+    """Clearing does not restore or replace the part's diffuse colour."""
+    pipe = VtkNodePipeline.from_dataset(array_dataset)
+    # Seeded diffuse colour: distinctive, and not the default mesh colour.
+    pipe.actor.GetProperty().SetDiffuseColor(0.11, 0.22, 0.33)
+
+    pipe.clear_color_variable()
+
+    assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
+        (0.11, 0.22, 0.33)
+    )
+
+

From 361c20ec373e9d8755db50808e25f4d70d0f3aa9 Mon Sep 17 00:00:00 2001
From: pyansys-ci-bot <92810346+pyansys-ci-bot@users.noreply.github.com>
Date: Fri, 28 Aug 2026 19:51:28 +0000
Subject: [PATCH 7/8] chore: adding changelog file 51.added.md
 [dependabot-skip]

---
 doc/changelog.d/51.added.md | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 doc/changelog.d/51.added.md

diff --git a/doc/changelog.d/51.added.md b/doc/changelog.d/51.added.md
new file mode 100644
index 00000000..d9507670
--- /dev/null
+++ b/doc/changelog.d/51.added.md
@@ -0,0 +1 @@
+Remote rendering 3.1b - implement per-part apply logic on the renderer and node pipeline

From 0c503624220fca2ade48f6f713052b8a271dc6d2 Mon Sep 17 00:00:00 2001
From: Laura Kasian <lkasian@synopsys.com>
Date: Mon, 31 Aug 2026 07:14:07 -0700
Subject: [PATCH 8/8] move remaining three vtk calls to node pipeline

---
 .../visor/viewer/renderer/local_renderer.py   |  21 ++-
 src/ansys/visor/viewer/vtk/node_pipeline.py   |  43 +++++
 tests/unit/renderer/test_local_renderer.py    | 163 +++++-------------
 tests/unit/vtk/test_node_pipeline.py          |  80 +++++++++
 4 files changed, 177 insertions(+), 130 deletions(-)

diff --git a/src/ansys/visor/viewer/renderer/local_renderer.py b/src/ansys/visor/viewer/renderer/local_renderer.py
index 47913992..e0dd8670 100644
--- a/src/ansys/visor/viewer/renderer/local_renderer.py
+++ b/src/ansys/visor/viewer/renderer/local_renderer.py
@@ -160,8 +160,9 @@ def deregister_all(self) -> None:
     def apply_visibility(self, node_id: int, visible: bool) -> None:
         """See :meth:`IRenderer.apply_visibility`.
 
-        Mutates the actor itself, not its property.  An unknown *node_id*
-        is a logged no-op, never a raise.
+        Resolves the pipeline and delegates to
+        :meth:`VtkNodePipeline.set_visibility`.  An unknown *node_id* is a
+        logged no-op, never a raise.
         """
         pipe = self._pipelines.get(node_id)
         if pipe is None:
@@ -169,13 +170,14 @@ def apply_visibility(self, node_id: int, visible: bool) -> None:
                 "apply_visibility: no pipeline for node %s; skipping.", node_id
             )
             return
-        pipe.actor.SetVisibility(1 if visible else 0)
+        pipe.set_visibility(visible)
 
     def apply_opacity(self, node_id: int, opacity: float) -> None:
         """See :meth:`IRenderer.apply_opacity`.
 
-        Mutates the actor's property.  An unknown *node_id* is a logged
-        no-op, never a raise.
+        Resolves the pipeline and delegates to
+        :meth:`VtkNodePipeline.set_opacity`.  An unknown *node_id* is a
+        logged no-op, never a raise.
         """
         pipe = self._pipelines.get(node_id)
         if pipe is None:
@@ -183,15 +185,16 @@ def apply_opacity(self, node_id: int, opacity: float) -> None:
                 "apply_opacity: no pipeline for node %s; skipping.", node_id
             )
             return
-        pipe.actor.GetProperty().SetOpacity(opacity)
+        pipe.set_opacity(opacity)
 
     def apply_diffuse_color(
         self, node_id: int, r: float, g: float, b: float
     ) -> None:
         """See :meth:`IRenderer.apply_diffuse_color`.
 
-        Mutates the actor property's diffuse colour only.  An unknown
-        *node_id* is a logged no-op, never a raise.
+        Resolves the pipeline and delegates to
+        :meth:`VtkNodePipeline.set_diffuse_color`.  An unknown *node_id*
+        is a logged no-op, never a raise.
         """
         pipe = self._pipelines.get(node_id)
         if pipe is None:
@@ -199,7 +202,7 @@ def apply_diffuse_color(
                 "apply_diffuse_color: no pipeline for node %s; skipping.", node_id
             )
             return
-        pipe.actor.GetProperty().SetDiffuseColor(r, g, b)
+        pipe.set_diffuse_color(r, g, b)
 
     def apply_edge_visibility(self, node_id: int, edge_visible: bool) -> None:
         """No-op in Story 1.2. Phase 3 populates."""
diff --git a/src/ansys/visor/viewer/vtk/node_pipeline.py b/src/ansys/visor/viewer/vtk/node_pipeline.py
index 1e97dcc1..fa611e0b 100644
--- a/src/ansys/visor/viewer/vtk/node_pipeline.py
+++ b/src/ansys/visor/viewer/vtk/node_pipeline.py
@@ -127,6 +127,9 @@ def set_selected(self, selected: bool, diffuse_rgb: list[float]) -> None:
             The part's diffuse colour, re-applied unconditionally on both
             branches -- selection changes the ambient/diffuse lighting
             terms, it does not replace the part's colour.
+
+        Note: :meth:`set_diffuse_color` also writes ``SetDiffuseColor``;
+        this method is not a substitute for it and vice versa.
         """
         prop = self.actor.GetProperty()
         if selected:
@@ -138,6 +141,46 @@ def set_selected(self, selected: bool, diffuse_rgb: list[float]) -> None:
             prop.SetAmbient(0.0)
         prop.SetDiffuseColor(*diffuse_rgb)
 
+    def set_visibility(self, visible: bool) -> None:
+        """Show or hide this part.
+
+        Mutates the actor itself, not its property.
+
+        Parameters
+        ----------
+        visible:
+            Target state.  Absolute, never a toggle.
+        """
+        self.actor.SetVisibility(1 if visible else 0)
+
+    def set_opacity(self, opacity: float) -> None:
+        """Set this part's opacity.
+
+        Mutates the actor's property.
+
+        Parameters
+        ----------
+        opacity:
+            The opacity value to apply, passed through unchanged.
+        """
+        self.actor.GetProperty().SetOpacity(opacity)
+
+    def set_diffuse_color(self, r: float, g: float, b: float) -> None:
+        """Set this part's diffuse colour.
+
+        Mutates the actor property's diffuse colour only.
+
+        Parameters
+        ----------
+        r, g, b:
+            The diffuse colour components, passed through unchanged.
+
+        Note: :meth:`set_selected` also writes ``SetDiffuseColor`` on both
+        of its branches; this method is not a substitute for it and vice
+        versa.
+        """
+        self.actor.GetProperty().SetDiffuseColor(r, g, b)
+
     def set_color_variable(
         self,
         association: VisorVtkVariableType,
diff --git a/tests/unit/renderer/test_local_renderer.py b/tests/unit/renderer/test_local_renderer.py
index 8fc9bfb2..ac4c9266 100644
--- a/tests/unit/renderer/test_local_renderer.py
+++ b/tests/unit/renderer/test_local_renderer.py
@@ -6,11 +6,11 @@
 1.  Node lifecycle  -- register_node / deregister_node (the non-trivial seam).
 2.  Interface conformance -- NullRenderer and VisorLocalRenderer both satisfy
     IRenderer's abstract contract.
-3.  Per-part visual mutations -- visibility, opacity and diffuse colour
-    mutate the resolved pipeline's VTK objects directly; selection and
-    colour variable resolve the pipeline and delegate to VtkNodePipeline
-    (their VTK effects are asserted in tests/unit/vtk/test_node_pipeline.py);
-    edge visibility and the colour-variable range refresh stay no-ops.
+3.  Per-part visual mutations -- visibility, opacity, diffuse colour,
+    selection and colour variable all resolve the pipeline and delegate to
+    VtkNodePipeline (their VTK effects are asserted in
+    tests/unit/vtk/test_node_pipeline.py); edge visibility and the
+    colour-variable range refresh stay no-ops.
 4.  Camera round-trip -- reset_camera, sync_camera / get_camera_state.
 5.  Render / flush delegation.
 6.  pick_geometry -- vertex, edge, face modes.
@@ -21,7 +21,6 @@
 from unittest.mock import MagicMock, patch
 
 import pytest
-from vtkmodules.vtkRenderingCore import vtkActor
 
 from ansys.visor.viewer.core.visor_enums import VisorVtkVariableType
 from ansys.visor.viewer.renderer.base import IRenderer
@@ -97,27 +96,6 @@ def GetNextActor(self): # noqa: N802
         return a
 
 
-class _DummyPipeline:
-    """VtkNodePipeline stand-in holding a *real* vtkActor.
-
-    The actor is real so that a test can read the mutated value back off
-    the VTK object (``GetVisibility``, ``GetProperty().GetOpacity()``,
-    ``GetProperty().GetDiffuseColor()``) rather than merely recording that
-    some call was made -- a MagicMock would pass even if the production
-    code mutated the wrong object or the wrong field.
-
-    The three delegated mutations are MagicMocks, because from this module
-    the behaviour under test is *that the renderer resolved and delegated*.
-    Their VTK effects are asserted against real objects in
-    ``tests/unit/vtk/test_node_pipeline.py``.
-    """
-
-    def __init__(self):
-        self.actor = vtkActor()
-        self.set_selected = MagicMock(name="set_selected")
-        self.set_color_variable = MagicMock(name="set_color_variable")
-        self.clear_color_variable = MagicMock(name="clear_color_variable")
-
 
 # ---------------------------------------------------------------------------
 # Fixture: VisorLocalRenderer with all VTK infrastructure mocked
@@ -381,42 +359,33 @@ def test_refresh_color_variable_range(self, renderer):
 
 
 # ===========================================================================
-# 3b.  Inline apply bodies: visibility, opacity, diffuse colour
+# 3b.  Delegated apply bodies: visibility, opacity, diffuse colour,
+#      selection, colour variable
 #
-#      Each mutation is read back off a real vtkActor, and each miss branch
-#      (unknown node id) is asserted separately.
+#      The VTK effects of these live on VtkNodePipeline and are asserted in
+#      tests/unit/vtk/test_node_pipeline.py.  What is asserted here is that
+#      the renderer resolved the pipeline and delegated with the arguments
+#      it was given, and that an unknown node id is a logged no-op.
 # ===========================================================================
 
-class TestInlineApplyBodies:
+class TestDelegatedApplyBodies:
 
     # ------------------------------------------------------------------
-    # visibility -- mutates the actor itself
+    # apply_visibility
     # ------------------------------------------------------------------
 
-    def test_apply_visibility_shows_actor(self, renderer):
-        """apply_visibility(True) leaves the actor's visibility flag set."""
-        pipe = _DummyPipeline()
-        pipe.actor.SetVisibility(0)
+    def test_apply_visibility_delegates_to_pipeline(self, renderer):
+        """The visibility flag is passed straight through."""
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         renderer.apply_visibility(4, True)
 
-        assert pipe.actor.GetVisibility() == 1
-
-    def test_apply_visibility_hides_actor(self, renderer):
-        """apply_visibility(False) leaves the actor's visibility flag clear."""
-        pipe = _DummyPipeline()
-        pipe.actor.SetVisibility(1)
-        renderer._pipelines[4] = pipe
-
-        renderer.apply_visibility(4, False)
-
-        assert pipe.actor.GetVisibility() == 0
+        pipe.set_visibility.assert_called_once_with(True)
 
     def test_apply_visibility_unknown_node_id_is_logged_no_op(self, renderer):
-        """An unregistered node id logs at debug, does not raise, mutates nothing."""
-        pipe = _DummyPipeline()
-        pipe.actor.SetVisibility(1)
+        """An unregistered node id logs at debug, does not raise, delegates nothing."""
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         with patch(
@@ -425,39 +394,24 @@ def test_apply_visibility_unknown_node_id_is_logged_no_op(self, renderer):
             renderer.apply_visibility(9999, False)  # must not raise
 
         mock_logger.debug.assert_called_once()
-        assert pipe.actor.GetVisibility() == 1
+        pipe.set_visibility.assert_not_called()
 
     # ------------------------------------------------------------------
-    # opacity -- mutates the actor's property
+    # apply_opacity
     # ------------------------------------------------------------------
 
-    def test_apply_opacity_sets_property_opacity(self, renderer):
-        """apply_opacity writes the requested value onto the actor property."""
-        pipe = _DummyPipeline()
+    def test_apply_opacity_delegates_to_pipeline(self, renderer):
+        """The opacity value is passed straight through."""
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         renderer.apply_opacity(4, 0.25)
 
-        assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.25)
-
-    def test_apply_opacity_does_not_touch_visibility_or_diffuse_color(self, renderer):
-        """Opacity lands on the property's opacity field and nothing else."""
-        pipe = _DummyPipeline()
-        pipe.actor.SetVisibility(0)
-        pipe.actor.GetProperty().SetDiffuseColor(0.25, 0.5, 0.75)
-        renderer._pipelines[4] = pipe
-
-        renderer.apply_opacity(4, 0.25)
-
-        assert pipe.actor.GetVisibility() == 0
-        assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
-            (0.25, 0.5, 0.75)
-        )
+        pipe.set_opacity.assert_called_once_with(0.25)
 
     def test_apply_opacity_unknown_node_id_is_logged_no_op(self, renderer):
-        """An unregistered node id logs at debug, does not raise, mutates nothing."""
-        pipe = _DummyPipeline()
-        pipe.actor.GetProperty().SetOpacity(0.75)
+        """An unregistered node id logs at debug, does not raise, delegates nothing."""
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         with patch(
@@ -466,43 +420,24 @@ def test_apply_opacity_unknown_node_id_is_logged_no_op(self, renderer):
             renderer.apply_opacity(9999, 0.25)  # must not raise
 
         mock_logger.debug.assert_called_once()
-        assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.75)
+        pipe.set_opacity.assert_not_called()
 
     # ------------------------------------------------------------------
-    # diffuse colour -- mutates the actor property's DiffuseColor
+    # apply_diffuse_color
     # ------------------------------------------------------------------
 
-    def test_apply_diffuse_color_sets_property_diffuse_color(self, renderer):
-        """apply_diffuse_color writes r, g, b onto the property's diffuse colour."""
-        pipe = _DummyPipeline()
+    def test_apply_diffuse_color_delegates_to_pipeline(self, renderer):
+        """r, g, b are passed straight through."""
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         renderer.apply_diffuse_color(4, 1.0, 0.0, 0.0)
 
-        assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
-            (1.0, 0.0, 0.0)
-        )
-
-    def test_apply_diffuse_color_does_not_touch_ambient_color_or_opacity(
-        self, renderer
-    ):
-        """SetDiffuseColor, not SetColor or SetAmbientColor, and opacity is left alone."""
-        pipe = _DummyPipeline()
-        pipe.actor.GetProperty().SetAmbientColor(0.25, 0.5, 0.75)
-        pipe.actor.GetProperty().SetOpacity(0.75)
-        renderer._pipelines[4] = pipe
-
-        renderer.apply_diffuse_color(4, 1.0, 0.0, 0.0)
-
-        assert pipe.actor.GetProperty().GetAmbientColor() == pytest.approx(
-            (0.25, 0.5, 0.75)
-        )
-        assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.75)
+        pipe.set_diffuse_color.assert_called_once_with(1.0, 0.0, 0.0)
 
     def test_apply_diffuse_color_unknown_node_id_is_logged_no_op(self, renderer):
-        """An unregistered node id logs at debug, does not raise, mutates nothing."""
-        pipe = _DummyPipeline()
-        pipe.actor.GetProperty().SetDiffuseColor(0.25, 0.5, 0.75)
+        """An unregistered node id logs at debug, does not raise, delegates nothing."""
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         with patch(
@@ -511,21 +446,7 @@ def test_apply_diffuse_color_unknown_node_id_is_logged_no_op(self, renderer):
             renderer.apply_diffuse_color(9999, 1.0, 0.0, 0.0)  # must not raise
 
         mock_logger.debug.assert_called_once()
-        assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
-            (0.25, 0.5, 0.75)
-        )
-
-
-# ===========================================================================
-# 3c.  Delegated apply bodies: selection, colour variable
-#
-#      The VTK effects of these live on VtkNodePipeline and are asserted in
-#      tests/unit/vtk/test_node_pipeline.py.  What is asserted here is that
-#      the renderer resolved the pipeline and delegated with the arguments
-#      it was given, and that an unknown node id is a logged no-op.
-# ===========================================================================
-
-class TestDelegatedApplyBodies:
+        pipe.set_diffuse_color.assert_not_called()
 
     # ------------------------------------------------------------------
     # apply_selected
@@ -533,7 +454,7 @@ class TestDelegatedApplyBodies:
 
     def test_apply_selected_delegates_to_pipeline(self, renderer):
         """Selection state and the given colour are passed straight through."""
-        pipe = _DummyPipeline()
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         renderer.apply_selected(4, True, [1.0, 0.0, 0.0])
@@ -542,7 +463,7 @@ def test_apply_selected_delegates_to_pipeline(self, renderer):
 
     def test_apply_selected_unknown_node_id_is_logged_no_op(self, renderer):
         """An unregistered node id logs at debug, does not raise, delegates nothing."""
-        pipe = _DummyPipeline()
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         with patch(
@@ -559,7 +480,7 @@ def test_apply_selected_unknown_node_id_is_logged_no_op(self, renderer):
 
     def test_apply_color_variable_delegates_with_given_arguments(self, renderer):
         """The association is forwarded unchanged; spectrum_id is not forwarded."""
-        pipe = _DummyPipeline()
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         renderer.apply_color_variable(
@@ -572,7 +493,7 @@ def test_apply_color_variable_delegates_with_given_arguments(self, renderer):
 
     def test_apply_color_variable_unknown_node_id_is_logged_no_op(self, renderer):
         """An unregistered node id logs at debug, does not raise, delegates nothing."""
-        pipe = _DummyPipeline()
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         with patch(
@@ -590,7 +511,7 @@ def test_apply_color_variable_unknown_node_id_is_logged_no_op(self, renderer):
     # ------------------------------------------------------------------
 
     def test_clear_color_variable_delegates_to_pipeline(self, renderer):
-        pipe = _DummyPipeline()
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         renderer.clear_color_variable(4)
@@ -599,7 +520,7 @@ def test_clear_color_variable_delegates_to_pipeline(self, renderer):
 
     def test_clear_color_variable_unknown_node_id_is_logged_no_op(self, renderer):
         """An unregistered node id logs at debug, does not raise, delegates nothing."""
-        pipe = _DummyPipeline()
+        pipe = MagicMock(name="pipeline")
         renderer._pipelines[4] = pipe
 
         with patch(
diff --git a/tests/unit/vtk/test_node_pipeline.py b/tests/unit/vtk/test_node_pipeline.py
index 96115c51..5a03955a 100644
--- a/tests/unit/vtk/test_node_pipeline.py
+++ b/tests/unit/vtk/test_node_pipeline.py
@@ -222,6 +222,86 @@ def test_set_selected_false_leaves_ambient_color_untouched(poly_dataset):
     )
 
 
+# ---------------------------------------------------------------------------
+# set_visibility
+# ---------------------------------------------------------------------------
+
+def test_set_visibility_true_shows_actor(poly_dataset):
+    """set_visibility(True) leaves the actor's visibility flag set."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+    pipe.actor.SetVisibility(0)
+
+    pipe.set_visibility(True)
+
+    assert pipe.actor.GetVisibility() == 1
+
+
+def test_set_visibility_false_hides_actor(poly_dataset):
+    """set_visibility(False) leaves the actor's visibility flag clear."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+    pipe.actor.SetVisibility(1)
+
+    pipe.set_visibility(False)
+
+    assert pipe.actor.GetVisibility() == 0
+
+
+# ---------------------------------------------------------------------------
+# set_opacity
+# ---------------------------------------------------------------------------
+
+def test_set_opacity_sets_property_opacity(poly_dataset):
+    """set_opacity writes the requested value onto the actor property."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+
+    pipe.set_opacity(0.25)
+
+    assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.25)
+
+
+def test_set_opacity_does_not_touch_visibility_or_diffuse_color(poly_dataset):
+    """Opacity lands on the property's opacity field and nothing else."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+    pipe.actor.SetVisibility(0)
+    pipe.actor.GetProperty().SetDiffuseColor(0.25, 0.5, 0.75)
+
+    pipe.set_opacity(0.25)
+
+    assert pipe.actor.GetVisibility() == 0
+    assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
+        (0.25, 0.5, 0.75)
+    )
+
+
+# ---------------------------------------------------------------------------
+# set_diffuse_color
+# ---------------------------------------------------------------------------
+
+def test_set_diffuse_color_sets_property_diffuse_color(poly_dataset):
+    """set_diffuse_color writes r, g, b onto the property's diffuse colour."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+
+    pipe.set_diffuse_color(1.0, 0.0, 0.0)
+
+    assert pipe.actor.GetProperty().GetDiffuseColor() == pytest.approx(
+        (1.0, 0.0, 0.0)
+    )
+
+
+def test_set_diffuse_color_does_not_touch_ambient_color_or_opacity(poly_dataset):
+    """SetDiffuseColor, not SetColor or SetAmbientColor, and opacity is left alone."""
+    pipe = VtkNodePipeline.from_dataset(poly_dataset)
+    pipe.actor.GetProperty().SetAmbientColor(0.25, 0.5, 0.75)
+    pipe.actor.GetProperty().SetOpacity(0.75)
+
+    pipe.set_diffuse_color(1.0, 0.0, 0.0)
+
+    assert pipe.actor.GetProperty().GetAmbientColor() == pytest.approx(
+        (0.25, 0.5, 0.75)
+    )
+    assert pipe.actor.GetProperty().GetOpacity() == pytest.approx(0.75)
+
+
 # ---------------------------------------------------------------------------
 # set_color_variable
 # ---------------------------------------------------------------------------