fixup! 3Delight ShaderNetworkAlgo : Translate UsdPreviewSurface to 3D…

…elight

Fix opacity cutoff

python/IECoreDelightTest/ShaderNetworkAlgoTest.py

@@ -129,9 +129,10 @@ def testConvertUSDOpacity( self ) :
 		#
 		# https://github.com/usd-wg/assets/tree/main/test_assets/AlphaBlendModeTest
 		#
-		# > Note : the leftmost texture is incorrect, because USD expects the texture
-		# > (which has unpremultiplied alpha) to be loaded unmodified, but OIIO/Cycles
-		# > appear to premultiply it during loading.
+		# > Note : the "cutoff" positions are incorrect, because 3Delight's colorspace
+		# > transformation of the sRGB PNG textures also affects their alpha channel.
+		# > Loading these textures with `sourceColorSpace`=`raw` results in the correct
+		# > cutoff positions.
 
 		for opacity in ( 0.25, 1.0, None ) :
 			for opacityThreshold in ( 0.0, 0.5, None ) :
@@ -184,7 +185,7 @@ def testConvertUSDOpacity( self ) :
 					)
 					for c in "XYZ" :
 						multiplyInput = convertedNetwork.input( ( "previewSurfaceOpacityMultiply", "input2{}".format( c ) ) )
-						self.assertEqual( multiplyInput, "previewSurfaceOpacityCompare" )
+						self.assertEqual( multiplyInput, ( "previewSurfaceOpacityCompare", "success" ) )
 
 					self.assertEqual(
 						convertedNetwork.input( ( "previewSurfaceOpacityCompare", "a" ) ),

src/IECoreDelight/ShaderNetworkAlgo.cpp

@@ -470,6 +470,7 @@ const InternedString g_specularColorDelightParameter( "specular_color" );
 const InternedString g_specularIORParameter( "specular_IOR" );
 const InternedString g_specularRoughnessParameter( "specular_roughness" );
 const InternedString g_stParameter( "st" );
+const InternedString g_successParameter( "success" );
 const InternedString g_textureFileParameter( "texture:file" );
 const InternedString g_textureFormatParameter( "texture:format" );
 const InternedString g_textureOutputParameter( "outColor" );
@@ -845,9 +846,9 @@ void convertUSDShaders( ShaderNetwork *shaderNetwork )
 					ShaderPtr multiplyShader = new Shader( "multiplyDivide" );
 					const InternedString multiplyHandle = shaderNetwork->addShader( handle.string() + "OpacityMultiply", std::move( multiplyShader ) );
 					shaderNetwork->addConnection( ShaderNetwork::Connection( opacityInput, { multiplyHandle, g_input1Parameter } ) );
-					shaderNetwork->addConnection( ShaderNetwork::Connection( compareHandle, { multiplyHandle, g_input2XParameter } ) );
-					shaderNetwork->addConnection( ShaderNetwork::Connection( compareHandle, { multiplyHandle, g_input2YParameter } ) );
-					shaderNetwork->addConnection( ShaderNetwork::Connection( compareHandle, { multiplyHandle, g_input2ZParameter } ) );
+					shaderNetwork->addConnection( ShaderNetwork::Connection( { compareHandle, g_successParameter }, { multiplyHandle, g_input2XParameter } ) );
+					shaderNetwork->addConnection( ShaderNetwork::Connection( { compareHandle, g_successParameter }, { multiplyHandle, g_input2YParameter } ) );
+					shaderNetwork->addConnection( ShaderNetwork::Connection( { compareHandle, g_successParameter }, { multiplyHandle, g_input2ZParameter } ) );
 					shaderNetwork->removeConnection( ShaderNetwork::Connection( opacityInput, { handle, g_opacityParameter } ) );
 					shaderNetwork->addConnection( ShaderNetwork::Connection( { multiplyHandle, g_oOutputParameter }, { handle, g_opacityParameter } ) );
 				}