Replace OSL C++ Material node with data driven implementation (AcademySoftwareFoundation#2477)

Remove OSL C++ Material node in favour of data driven implementation.
Simplification of code export allows ignoring of node classification, which the OSL code generator doesn't need to emit the correct code.

Author: ld-kerley

libraries/stdlib/genosl/mx_surfacematerial.osl

@@ -0,0 +1,5 @@
+void mx_surfacematerial(surfaceshader surface, surfaceshader back, displacementshader disp, output MATERIAL result)
+{
+    float opacity_weight = clamp(surface.opacity, 0.0, 1.0);
+    result =  (surface.bsdf + surface.edf) * opacity_weight + transparent() * (1.0 - opacity_weight);
+}

libraries/stdlib/genosl/stdlib_genosl_impl.mtlx

@@ -12,7 +12,7 @@
   <!-- ======================================================================== -->
 
   <!-- <surfacematerial> -->
-  <implementation name="IM_surfacematerial_genosl" nodedef="ND_surfacematerial" target="genosl" />
+  <implementation name="IM_surfacematerial_genosl" nodedef="ND_surfacematerial" file="mx_surfacematerial.osl" function="mx_surfacematerial" target="genosl" />
 
   <!-- <surface_unlit> -->
   <implementation name="IM_surface_unlit_genosl" nodedef="ND_surface_unlit" file="mx_surface_unlit.osl" function="mx_surface_unlit" target="genosl" />

source/MaterialXGenOsl/Nodes/MaterialNodeOsl.cpp

@@ -13,7 +13,6 @@
 #include <MaterialXGenShader/Nodes/SourceCodeNode.h>
 
 #include <MaterialXGenOsl/Nodes/BlurNodeOsl.h>
-#include <MaterialXGenOsl/Nodes/MaterialNodeOsl.h>
 
 MATERIALX_NAMESPACE_BEGIN
 
@@ -35,12 +34,6 @@ OslShaderGenerator::OslShaderGenerator(TypeSystemPtr typeSystem) :
     registerImplementation("IM_blur_vector2_" + OslShaderGenerator::TARGET, BlurNodeOsl::create);
     registerImplementation("IM_blur_vector3_" + OslShaderGenerator::TARGET, BlurNodeOsl::create);
     registerImplementation("IM_blur_vector4_" + OslShaderGenerator::TARGET, BlurNodeOsl::create);
-
-    // <!-- <surface> -->
-    registerImplementation("IM_surface_" + OslShaderGenerator::TARGET, SourceCodeNode::create);
-
-    // <!-- <surfacematerial> -->
-    registerImplementation("IM_surfacematerial_" + OslShaderGenerator::TARGET, MaterialNodeOsl::create);
 }
 
 ShaderPtr OslShaderGenerator::generate(const string& name, ElementPtr element, GenContext& context) const
@@ -58,6 +51,7 @@ ShaderPtr OslShaderGenerator::generate(const string& name, ElementPtr element, G
     // Add global constants and type definitions
     emitTypeDefinitions(context, stage);
     emitLine("#define M_FLOAT_EPS 1e-8", stage, false);
+    emitLine("closure color null_closure() { closure color null_closure = 0; return null_closure; } ", stage, false);
     emitLineBreak(stage);
 
     // Set the include file to use for uv transformations,
@@ -180,22 +174,16 @@ ShaderPtr OslShaderGenerator::generate(const string& name, ElementPtr element, G
         }
     }
 
-    // Emit all texturing nodes. These are inputs to any
-    // closure/shader nodes and need to be emitted first.
-    emitFunctionCalls(graph, context, stage, ShaderNode::Classification::TEXTURE);
-
-    // Emit function calls for "root" closure/shader nodes.
-    // These will internally emit function calls for any dependent closure nodes upstream.
+    // Emit function calls for all nodes in the graph, starting each output
+    // port and walking backwards along the incoming connections
     for (ShaderGraphOutputSocket* socket : graph.getOutputSockets())
     {
         if (socket->getConnection())
         {
             const ShaderNode* upstream = socket->getConnection()->getNode();
-            if (upstream->getParent() == &graph &&
-                (upstream->hasClassification(ShaderNode::Classification::CLOSURE) ||
-                 upstream->hasClassification(ShaderNode::Classification::SHADER)))
+            if (upstream->getParent() == &graph)
             {
-                emitFunctionCall(*upstream, context, stage);
+                emitAllDependentFunctionCalls(*upstream, context, stage);
             }
         }
     }
@@ -304,38 +292,21 @@ ShaderPtr OslShaderGenerator::createShader(const string& name, ElementPtr elemen
     return shader;
 }
 
-void OslShaderGenerator::emitFunctionCalls(const ShaderGraph& graph, GenContext& context, ShaderStage& stage, uint32_t classification) const
+// TODO - determine it's better if this lives in ShaderGenerator as a useful API function
+void OslShaderGenerator::emitAllDependentFunctionCalls(const ShaderNode& node, GenContext& context, ShaderStage& stage) const
 {
-    // Special handling for closures functions.
-    if ((classification & ShaderNode::Classification::CLOSURE) != 0)
+    // Check if it's emitted already.
+    if (!stage.isEmitted(node, context))
     {
-        // Emit function calls for closures connected to the outputs.
-        // These will internally emit other closure function calls
-        // for upstream nodes if needed.
-        for (ShaderGraphOutputSocket* outputSocket : graph.getOutputSockets())
+        // Emit function calls for upstream connected nodes
+        for (const auto& input : node.getInputs())
         {
-            const ShaderNode* upstream = outputSocket->getConnection() ? outputSocket->getConnection()->getNode() : nullptr;
-            if (upstream && upstream->hasClassification(classification))
+            if (const auto& upstream = input->getConnectedSibling())
             {
-                emitFunctionCall(*upstream, context, stage);
+                emitAllDependentFunctionCalls(*upstream, context, stage);
             }
         }
-    }
-    else
-    {
-        // Not a closures graph so just generate all
-        // function calls in order.
-        ShaderGenerator::emitFunctionCalls(graph, context, stage, classification);
-    }
-}
-
-void OslShaderGenerator::emitFunctionBodyBegin(const ShaderNode& node, GenContext&, ShaderStage& stage, Syntax::Punctuation punc) const
-{
-    emitScopeBegin(stage, punc);
-
-    if (node.hasClassification(ShaderNode::Classification::SHADER) || node.hasClassification(ShaderNode::Classification::CLOSURE))
-    {
-        emitLine("closure color null_closure = 0", stage);
+        stage.addFunctionCall(node, context);
     }
 }
 

source/MaterialXGenOsl/Nodes/MaterialNodeOsl.h

@@ -43,12 +43,8 @@ class MX_GENOSL_API OslShaderGenerator : public ShaderGenerator
     /// the element and all dependencies upstream into shader code.
     ShaderPtr generate(const string& name, ElementPtr element, GenContext& context) const override;
 
-    /// Add all function calls for a graph. If a classification mask is given only functions for
-    /// nodes matching this classification will be emitted.
-    void emitFunctionCalls(const ShaderGraph& graph, GenContext& context, ShaderStage& stage, uint32_t classification = 0u) const override;
-
-    /// Emit code for starting a new function body.
-    void emitFunctionBodyBegin(const ShaderNode& node, GenContext& context, ShaderStage& stage, Syntax::Punctuation punc = Syntax::CURLY_BRACKETS) const override;
+    /// Add all function calls for a node, and all upstream nodes.
+    void emitAllDependentFunctionCalls(const ShaderNode& node, GenContext& context, ShaderStage& stage) const;
 
     /// Unique identifier for this generator target
     static const string TARGET;

source/MaterialXGenOsl/OslShaderGenerator.cpp

@@ -388,7 +388,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<ScalarTypeSyntax>(
             this,
             "BSDF",
-            "null_closure",
+            "null_closure()",
             "0",
             "closure color",
             "#define BSDF closure color"));
@@ -398,7 +398,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<ScalarTypeSyntax>(
             this,
             "EDF",
-            "null_closure",
+            "null_closure()",
             "0",
             "closure color",
             "#define EDF closure color"));
@@ -408,7 +408,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<ScalarTypeSyntax>(
             this,
             "VDF",
-            "null_closure",
+            "null_closure()",
             "0",
             "closure color",
             "#define VDF closure color"));
@@ -418,7 +418,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<AggregateTypeSyntax>(
             this,
             "surfaceshader",
-            "surfaceshader(null_closure, null_closure, 1.0)",
+            "surfaceshader(null_closure(), null_closure(), 1.0)",
             "{ 0, 0, 1.0 }",
             "closure color",
             "struct surfaceshader { closure color bsdf; closure color edf; float opacity; };"));
@@ -428,7 +428,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<ScalarTypeSyntax>(
             this,
             "volumeshader",
-            "null_closure",
+            "null_closure()",
             "0",
             "closure color",
             "#define volumeshader closure color"));
@@ -448,7 +448,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<ScalarTypeSyntax>(
             this,
             "lightshader",
-            "null_closure",
+            "null_closure()",
             "0",
             "closure color",
             "#define lightshader closure color"));
@@ -458,7 +458,7 @@ OslSyntax::OslSyntax(TypeSystemPtr typeSystem) : Syntax(typeSystem)
         std::make_shared<ScalarTypeSyntax>(
             this,
             "MATERIAL",
-            "null_closure",
+            "null_closure()",
             "0",
             "closure color",
             "#define MATERIAL closure color"));