Cycles : Correct setting of background light's lightgroup

Changes.md

@@ -5,6 +5,7 @@ Fixes
 -----
 
 - DisplayTransform : Fixed missing `view` presets when `display` is at the default value (#5392).
+- Cycles : The background light's lightgroup is now being set correctly as well as adding a way to set a lightgroup from CyclesOptions when a CyclesBackground is being used instead.
 
 1.3.0.0 (relative to 1.2.10.0)
 =======

python/GafferCyclesTest/IECoreCyclesPreviewTest/RendererTest.py

@@ -1128,7 +1128,7 @@ def testShaderSubstitutions( self ) :
 		self.assertEqual( self.__colorAtUV( image, imath.V2f( 0.48, 0.5 ) ), imath.Color4f( 1, 0, 0, 1 ) )
 		self.assertEqual( self.__colorAtUV( image, imath.V2f( 0.52, 0.5 ) ), imath.Color4f( 0, 1, 0, 1 ) )
 
-	def __colorAtUV( self, image, uv, channelName = "" ) :
+	def __colorAtUV( self, image, uv, channelName = "", alpha = True ) :
 
 		dimensions = image.dataWindow.size() + imath.V2i( 1 )
 
@@ -1140,7 +1140,11 @@ def __colorAtUV( self, image, uv, channelName = "" ) :
 		if c != "":
 			c = "%s." % channelName
 
-		return imath.Color4f( image[c+"R"][i], image[c+"G"][i], image[c+"B"][i], image[c+"A"][i] )
+		a = 1
+		if alpha:
+			a = image[c+"A"][i]
+
+		return imath.Color4f( image[c+"R"][i], image[c+"G"][i], image[c+"B"][i], a )
 
 	def __testCustomAttributeType( self, primitive, prefix, customAttribute, outputPlug, data, expectedResult, maxDifference = 0.0 ) :
 
@@ -1823,5 +1827,86 @@ def testUnsupportedShaderParameters( self ) :
 			"Unsupported socket type `transform` for socket `ob_tfm` on node .*"
 		)
 
+	def testBackgroundLightgroup( self ) :
+
+		renderer = GafferScene.Private.IECoreScenePreview.Renderer.create(
+			"Cycles",
+			GafferScene.Private.IECoreScenePreview.Renderer.RenderType.Interactive,
+		)
+
+		renderer.output(
+			"testOutput",
+			IECoreScene.Output(
+				"test",
+				"ieDisplay",
+				"rgba",
+				{
+					"driverType" : "ImageDisplayDriver",
+					"handle" : "testOutput",
+				}
+			)
+		)
+
+		renderer.output(
+			"testEnvOutput",
+			IECoreScene.Output(
+				"env",
+				"ieDisplay",
+				"lg env",
+				{
+					"driverType" : "ImageDisplayDriver",
+					"handle" : "testEnvOutput",
+				}
+			)
+		)
+
+		renderer.light(
+			"/light",
+			None,
+			renderer.attributes( IECore.CompoundObject ( {
+				"cycles:light" : IECoreScene.ShaderNetwork(
+					shaders = {
+						"output" : IECoreScene.Shader( "background_light", "cycles:light", { "color" : imath.Color3f( 0, 1, 0 ), "lightgroup" : "env" } ),
+					},
+					output = "output",
+				),
+			} ) )
+		)
+
+		plane = renderer.object(
+			"/plane",
+			IECoreScene.MeshPrimitive.createPlane(
+				imath.Box2f( imath.V2f( -1 ), imath.V2f( 1 ) ),
+			),
+			renderer.attributes( IECore.CompoundObject ( {
+				"cycles:surface" : IECoreScene.ShaderNetwork(
+					shaders = {
+						"output" : IECoreScene.Shader(
+							"principled_bsdf", "cycles:shader",
+							{ "base_color" : imath.Color3f( 1, 1, 1 ) }
+						),
+					},
+					output = "output",
+				)
+			} ) )
+		)
+		## \todo Default camera is facing down +ve Z but should be facing
+		# down -ve Z.
+		plane.transform( imath.M44f().translate( imath.V3f( 0, 0, 1 ) ) )
+
+		renderer.render()
+		time.sleep( 2 )
+
+		image = IECoreImage.ImageDisplayDriver.storedImage( "testEnvOutput" )
+		self.assertIsInstance( image, IECoreImage.ImagePrimitive )
+
+		# Slightly off-centre, to avoid triangle edge artifact in centre of image.
+		testPixel = self.__colorAtUV( image, imath.V2f( 0.55 ), "env", False )
+		self.assertEqual( testPixel.r, 0 )
+		self.assertGreater( testPixel.g, 0.99 )
+		self.assertEqual( testPixel.b, 0 )
+
+		del plane
+
 if __name__ == "__main__":
 	unittest.main()

python/GafferCyclesUI/CyclesOptionsUI.py

@@ -302,6 +302,9 @@ def __backgroundSummary( plug ) :
 	if plug["bgTransparentRoughnessThreshold"]["enabled"].getValue() :
 		info.append( "Roughness Threshold {}".format( plug["bgTransparentRoughnessThreshold"]["value"].getValue() ) )
 
+	if plug["bgLightgroup"]["enabled"].getValue() :
+		info.append( "Lightgroup {}".format( plug["bgLightgroup"]["value"].getValue() ) )
+
 	for childName in ( "Camera", "Diffuse", "Glossy", "Transmission", "Shadow", "Scatter" ) :
 		if plug["bg" + childName + "Visibility"]["enabled"].getValue() :
 			info.append( IECore.CamelCase.toSpaced( childName ) + ( " On" if plug["bg" + childName + "Visibility"]["value"].getValue() else " Off" ) )
@@ -1309,6 +1312,20 @@ def __devicesPreset() :
 
 		],
 
+		"options.bgLightgroup" : [
+
+			"description",
+			"""
+			The background lightgroup name. This will only be set if a
+			CyclesBackground is used instead of a background light,
+			otherwise it will use the lightgroup name from the light itself.
+			""",
+
+			"layout:section", "Background",
+			"label", "Lightgroup",
+
+		],
+
 		# Film
 
 		"options.exposure" : [

src/GafferCycles/CyclesOptions.cpp

@@ -144,6 +144,8 @@ CyclesOptions::CyclesOptions( const std::string &name )
 
 	options->addChild( new Gaffer::NameValuePlug( "cycles:background:volume_step_size", new IECore::FloatData( 0.1f ), false, "volumeStepSize" ) );
 
+	options->addChild( new Gaffer::NameValuePlug( "cycles:background:lightgroup", new IECore::StringData( "" ), false, "bgLightgroup" ) );
+
 	// Film
 	options->addChild( new Gaffer::NameValuePlug( "cycles:film:exposure", new IECore::FloatData( 1.0f ), false, "exposure" ) );
 	options->addChild( new Gaffer::NameValuePlug( "cycles:film:pass_alpha_threshold", new IECore::FloatData( 0.5f ), false, "passAlphaThreshold" ) );

src/GafferCycles/IECoreCyclesPreview/Renderer.cpp

@@ -2459,8 +2459,9 @@ IECore::InternedString g_numBvhTimeStepsOptionName( "cycles:scene:num_bvh_time_s
 IECore::InternedString g_hairSubdivisionsOptionName( "cycles:scene:hair_subdivisions" );
 IECore::InternedString g_hairShapeOptionName( "cycles:scene:hair_shape" );
 IECore::InternedString g_textureLimitOptionName( "cycles:scene:texture_limit" );
-// Background shader
+// Background
 IECore::InternedString g_backgroundShaderOptionName( "cycles:background:shader" );
+IECore::InternedString g_backgroundLightgroupOptionName( "cycles:background:lightgroup" );
 //
 IECore::InternedString g_useFrameAsSeedOptionName( "cycles:integrator:useFrameAsSeed" );
 IECore::InternedString g_seedOptionName( "cycles:integrator:seed" );
@@ -2524,6 +2525,7 @@ class CyclesRenderer final : public IECoreScenePreview::Renderer
 #ifdef WITH_CYCLES_TEXTURE_CACHE
 				m_textureCacheParams( ccl::TextureCacheParams() ),
 #endif
+				m_backgroundLightgroup( ccl::ustring( "" ) ),
 				m_deviceName( g_defaultDeviceName ),
 				m_renderType( renderType ),
 				m_frame( 1 ),
@@ -2959,6 +2961,17 @@ class CyclesRenderer final : public IECoreScenePreview::Renderer
 							m_backgroundShader = nullptr;
 						}
 					}
+					else if( name == g_backgroundLightgroupOptionName )
+					{
+						if( value == nullptr )
+						{
+							m_backgroundLightgroup = ccl::ustring( "" );
+						}
+						else if ( const StringData *data = reportedCast<const StringData>( value, "option", name ) )
+						{
+							m_backgroundLightgroup = ccl::ustring( data->readable() );
+						}
+					}
 					else if( const Data *data = reportedCast<const Data>( value, "option", name ) )
 					{
 						SocketAlgo::setSocket( (ccl::Node*)background, input, data );
@@ -3387,11 +3400,14 @@ class CyclesRenderer final : public IECoreScenePreview::Renderer
 			}
 
 			ccl::Shader *lightShader = nullptr;
+			ccl::ustring lightGroup = ccl::ustring("");
+
 			for( ccl::Light *light : m_scene->lights )
 			{
 				if( light->get_light_type() == ccl::LIGHT_BACKGROUND )
 				{
 					lightShader = light->get_shader();
+					lightGroup = light->get_lightgroup();
 					break;
 				}
 			}
@@ -3403,14 +3419,17 @@ class CyclesRenderer final : public IECoreScenePreview::Renderer
 			if( m_backgroundShader )
 			{
 				background->set_shader( m_backgroundShader->shader() );
+				background->set_lightgroup( m_backgroundLightgroup );
 			}
 			else if( lightShader )
 			{
 				background->set_shader( lightShader );
+				background->set_lightgroup( lightGroup );
 			}
 			else
 			{
 				background->set_shader( m_scene->default_background );
+				background->set_lightgroup( m_backgroundLightgroup );
 			}
 
 			if( integrator->is_modified() )
@@ -3895,8 +3914,9 @@ class CyclesRenderer final : public IECoreScenePreview::Renderer
 		ccl::Background m_background;
 		ccl::Film m_film;
 
-		// Background shader
+		// Background
 		CyclesShaderPtr m_backgroundShader;
+		ccl::ustring m_backgroundLightgroup;
 
 		// Defaults
 		ccl::Camera m_cameraDefault;