Merge pull request #6211 from johnhaddon/contextProcessorsInShaders

Shader : Support inline ContextProcessors

Changes.md

@@ -9,6 +9,8 @@ Features
 Improvements
 ------------
 
+- Shader, ShaderPlug : Added support for ContextProcessor, Loop and Spreadsheet nodes to be used inline between shader nodes and as the terminal node connected to
+  ShaderAssignment and other shader-consuming nodes.
 - VisualiserTool : Changed `dataName` input widget for choosing the primitive variable to visualise to a list of available variable names for the current selection.
 - Tweaks nodes : Moved list of tweaks to a collapsible "Tweaks" section in the NodeEditor.
 - Viewer :
@@ -23,6 +25,9 @@ Fixes
   - Fixed bug where the value dragged from the visualiser would be slightly different from the initial value on button press. (#6191)
   - Fixed error when trying to visualise data unsupported data.
 - TweakPlug : Fixed preservation of geometric interpretation when tweaking V3f values.
+- Shader :
+  - Fixed handling of multiple consecutive Switch nodes in a shader network.
+  - Fixed leak of private `scene:shader:outputParameter` context variable.
 - ApplicationTest : Extended grace period when testing process name on slower hosts.
 - OpDialogue : Fixed `DefaultButton` handling.
 
@@ -35,6 +40,8 @@ API
   - The API is esoteric and was introduced extremely recently, so we believe nobody to be depending on it yet.
   - Without the ABI change, the API isn't usable for its original intended purpose anyway.
   - Backward compatibility is not trivial to maintain in this case.
+- PlugAlgo : Added `contextSensitiveSource()` method.
+- ShaderPlug : Added Python binding for `parameterSource()` method.
 
 1.5.2.0 (relative to 1.5.1.0)
 =======

include/Gaffer/PlugAlgo.h

@@ -48,6 +48,7 @@
 namespace Gaffer
 {
 
+IE_CORE_FORWARDDECLARE( Context )
 IE_CORE_FORWARDDECLARE( GraphComponent )
 IE_CORE_FORWARDDECLARE( ValuePlug )
 
@@ -77,6 +78,16 @@ std::invoke_result_t<Predicate, Plug *> findDestination( Plug *plug, Predicate &
 template<typename Predicate>
 std::invoke_result_t<Predicate, Plug *> findSource( Plug *plug, Predicate &&predicate );
 
+/// Similar to `Plug::source()`, but also traversing upstream through Switch,
+/// Spreadsheet, ContextProcessor and Loop nodes, taking into account their
+/// operation in the current context. Returns the source plug and also the context
+/// it is evaluated in.
+///
+/// > Note : If the current context contains a Canceller, then the returned context
+/// > will reference it too. If the context is stored for later usage, the canceller
+/// > should be removed.
+GAFFER_API std::tuple<const Plug *, ConstContextPtr> contextSensitiveSource( const Plug *plug );
+
 /// Conversion to and from `IECore::Data`
 /// =====================================
 

include/GafferScene/ShaderPlug.h

@@ -49,6 +49,8 @@
 namespace GafferScene
 {
 
+class Shader;
+
 /// Plug that accepts a Shader::outPlug() as input, and provides
 /// access to the shading network generated by the shader.
 class GAFFERSCENE_API ShaderPlug : public Gaffer::Plug
@@ -79,7 +81,8 @@ class GAFFERSCENE_API ShaderPlug : public Gaffer::Plug
 
 	private:
 
-		const Gaffer::Plug *shaderOutPlug() const;
+		struct ShaderContext;
+		const Gaffer::Plug * shaderOutPlug( ShaderContext &shaderContext ) const;
 
 };
 

python/GafferSceneTest/ShaderPlugTest.py

@@ -0,0 +1,83 @@
+##########################################################################
+#
+#  Copyright (c) 2025, Cinesite VFX Ltd. All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are
+#  met:
+#
+#      * Redistributions of source code must retain the above
+#        copyright notice, this list of conditions and the following
+#        disclaimer.
+#
+#      * Redistributions in binary form must reproduce the above
+#        copyright notice, this list of conditions and the following
+#        disclaimer in the documentation and/or other materials provided with
+#        the distribution.
+#
+#      * Neither the name of John Haddon nor the names of
+#        any other contributors to this software may be used to endorse or
+#        promote products derived from this software without specific prior
+#        written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+#  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+#  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+#  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+#  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+#  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+#  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+#  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+#  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+#  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+#  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+##########################################################################
+
+import unittest
+
+import imath
+
+import Gaffer
+import GafferScene
+import GafferSceneTest
+
+class ShaderPlugTest( GafferSceneTest.SceneTestCase ) :
+
+	def testContextProcessorInput( self ) :
+
+		shader1 = GafferSceneTest.TestShader()
+		shader1["type"].setValue( "test:surface" )
+		shader1["parameters"]["c"].setValue( imath.Color3f( 1 ) )
+		shader2 = GafferSceneTest.TestShader()
+		shader2["type"].setValue( "test:surface" )
+		shader2["parameters"]["c"].setValue( imath.Color3f( 2 ) )
+
+		nameSwitch = Gaffer.NameSwitch()
+		nameSwitch.setup( shader2["out"] )
+		nameSwitch["selector"].setValue( "${which}")
+		nameSwitch["in"][0]["name"].setValue( "one" )
+		nameSwitch["in"][0]["value"].setInput( shader1["out"] )
+		nameSwitch["in"][1]["name"].setValue( "two" )
+		nameSwitch["in"][1]["value"].setInput( shader2["out"] )
+
+		contextVariables = Gaffer.ContextVariables()
+		contextVariables.setup( nameSwitch["out"]["value"] )
+		contextVariables["in"].setInput( nameSwitch["out"]["value"] )
+		contextVariables["variables"].addChild( Gaffer.NameValuePlug( "which", "two" ) )
+
+		shaderPlug = GafferScene.ShaderPlug()
+		shaderPlug.setInput( contextVariables["out"] )
+
+		self.assertEqual( shaderPlug.attributes()["test:surface"].outputShader().parameters["c"].value, imath.Color3f( 2 ) )
+
+	def testRejectsScenePlugInputFromContextProcessor( self ) :
+
+		contextVariables = Gaffer.ContextVariables()
+		contextVariables.setup( GafferScene.ScenePlug() )
+
+		shaderPlug = GafferScene.ShaderPlug()
+		self.assertFalse( shaderPlug.acceptsInput( contextVariables["out"] ) )
+
+if __name__ == "__main__":
+	unittest.main()