MDL 1.9 updates (#2102)

add new version to GenMDL and remove uniform restriction from material IOR

Minor updates:
- improve MDL printing by adding named parameters
- handle 1-element mixes (basically scale) above layers
- improve blur and height to normal to return something meaningful (before totally broken)
- improve non-material outputs that can be rendered, e.g. float3x3 and float4x4
- preparations for MDL 1.10
- remove shader parameters from the public MDL material interface. backsurfaceshader and displacementshader showed up with default values only after recent upstream changes

Author: krohmerNV

libraries/pbrlib/genmdl/pbrlib_genmdl_impl.mtlx

@@ -2,7 +2,7 @@
 <materialx version="1.39">
 
   <!-- <oren_nayar_diffuse_bsdf> -->
-  <implementation name="IM_oren_nayar_diffuse_bsdf_genmdl" nodedef="ND_oren_nayar_diffuse_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_oren_nayar_diffuse_bsdf(mxp_weight:{{weight}}, mxp_color:{{color}}, mxp_roughness:{{roughness}}, mxp_normal:{{normal}})" target="genmdl" />
+  <implementation name="IM_oren_nayar_diffuse_bsdf_genmdl" nodedef="ND_oren_nayar_diffuse_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_oren_nayar_diffuse_bsdf(mxp_weight:{{weight}}, mxp_color:{{color}}, mxp_roughness:{{roughness}}, mxp_normal:{{normal}}, mxp_energy_compensation:{{energy_compensation}})" target="genmdl" />
 
   <!-- <burley_diffuse_bsdf> -->
   <implementation name="IM_burley_diffuse_bsdf_genmdl" nodedef="ND_burley_diffuse_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_burley_diffuse_bsdf(mxp_weight:{{weight}}, mxp_color:{{color}}, mxp_roughness:{{roughness}}, mxp_normal:{{normal}})" target="genmdl" />
@@ -11,13 +11,13 @@
   <implementation name="IM_translucent_bsdf_genmdl" nodedef="ND_translucent_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_translucent_bsdf(mxp_weight:{{weight}}, mxp_color:{{color}}, mxp_normal:{{normal}})" target="genmdl" />
 
   <!-- <dielectric_bsdf> -->
-  <implementation name="IM_dielectric_bsdf_genmdl" nodedef="ND_dielectric_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_dielectric_bsdf(mxp_weight:{{weight}}, mxp_tint:{{tint}}, mxp_ior:{{ior}}, mxp_roughness:{{roughness}}, mxp_thinfilm_thickness:{{thinfilm_thickness}}, mxp_thinfilm_ior:{{thinfilm_ior}}, mxp_normal:{{normal}}, mxp_tangent:{{tangent}}, mxp_distribution:{{distribution}}, mxp_scatter_mode:{{scatter_mode}}, mxp_base:{{base}})" target="genmdl" />
+  <implementation name="IM_dielectric_bsdf_genmdl" nodedef="ND_dielectric_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_dielectric_bsdf(mxp_weight:{{weight}}, mxp_tint:{{tint}}, mxp_ior:{{ior}}, mxp_roughness:{{roughness}}, mxp_thinfilm_thickness:{{thinfilm_thickness}}, mxp_thinfilm_ior:{{thinfilm_ior}}, mxp_normal:{{normal}}, mxp_tangent:{{tangent}}, mxp_distribution:{{distribution}}, mxp_scatter_mode:{{scatter_mode}}, mxp_base:{{base}}, mxp_top_weight:{{top_weight}})" target="genmdl" />
 
   <!-- <conductor_bsdf> -->
   <implementation name="IM_conductor_bsdf_genmdl" nodedef="ND_conductor_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_conductor_bsdf(mxp_weight:{{weight}}, mxp_ior:{{ior}}, mxp_extinction:{{extinction}}, mxp_roughness:{{roughness}}, mxp_thinfilm_thickness:{{thinfilm_thickness}}, mxp_thinfilm_ior:{{thinfilm_ior}}, mxp_normal:{{normal}}, mxp_tangent:{{tangent}}, mxp_distribution:{{distribution}})" target="genmdl" />
 
   <!-- <generalized_schlick_bsdf> -->
-  <implementation name="IM_generalized_schlick_bsdf_genmdl" nodedef="ND_generalized_schlick_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_generalized_schlick_bsdf(mxp_weight:{{weight}}, mxp_color0:{{color0}}, mxp_color90:{{color90}}, mxp_exponent:{{exponent}},mxp_roughness:{{roughness}}, mxp_thinfilm_thickness:{{thinfilm_thickness}}, mxp_thinfilm_ior:{{thinfilm_ior}}, mxp_normal:{{normal}}, mxp_tangent:{{tangent}}, mxp_distribution:{{distribution}}, mxp_scatter_mode:{{scatter_mode}}, mxp_base:{{base}})" target="genmdl" />
+  <implementation name="IM_generalized_schlick_bsdf_genmdl" nodedef="ND_generalized_schlick_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_generalized_schlick_bsdf(mxp_weight:{{weight}}, mxp_color0:{{color0}}, mxp_color82:{{color82}}, mxp_color90:{{color90}}, mxp_exponent:{{exponent}},mxp_roughness:{{roughness}}, mxp_thinfilm_thickness:{{thinfilm_thickness}}, mxp_thinfilm_ior:{{thinfilm_ior}}, mxp_normal:{{normal}}, mxp_tangent:{{tangent}}, mxp_distribution:{{distribution}}, mxp_scatter_mode:{{scatter_mode}}, mxp_base:{{base}}, mxp_top_weight:{{top_weight}})" target="genmdl" />
 
   <!-- <subsurface_bsdf> -->
   <implementation name="IM_subsurface_bsdf_genmdl" nodedef="ND_subsurface_bsdf" sourcecode="materialx::pbrlib_{{MDL_VERSION_SUFFIX}}::mx_subsurface_bsdf(mxp_weight:{{weight}}, mxp_color:{{color}}, mxp_radius:{{radius}}, mxp_anisotropy:{{anisotropy}}, mxp_normal:{{normal}})" target="genmdl" />

libraries/stdlib/genmdl/stdlib_genmdl_impl.mtlx

@@ -695,7 +695,7 @@
   <implementation name="IM_combine3_vector3_genmdl" nodedef="ND_combine3_vector3" target="genmdl" sourcecode="float3( {{in1}},{{in2}},{{in3}} )" />
 
   <!-- <combine4> -->
-  <implementation name="IM_combine4_color4_genmdl" nodedef="ND_combine4_color4" target="genmdl" sourcecode="color4( {{in1}},{{in2}},{{in3}},{{in4}} )" />
+  <implementation name="IM_combine4_color4_genmdl" nodedef="ND_combine4_color4" target="genmdl" sourcecode="materialx::core::mk_color4( {{in1}},{{in2}},{{in3}},{{in4}} )" />
   <implementation name="IM_combine4_vector4_genmdl" nodedef="ND_combine4_vector4" target="genmdl" sourcecode="float4( {{in1}},{{in2}},{{in3}},{{in4}} )" />
 
   <!-- <creatematrix> -->

source/MaterialXGenMdl/MdlShaderGenerator.cpp

@@ -52,9 +52,11 @@ const string IMPORT_ALL = " import *";
 const string MDL_VERSION_1_6 = "1.6";
 const string MDL_VERSION_1_7 = "1.7";
 const string MDL_VERSION_1_8 = "1.8";
+const string MDL_VERSION_1_9 = "1.9";
 const string MDL_VERSION_SUFFIX_1_6 = "1_6";
 const string MDL_VERSION_SUFFIX_1_7 = "1_7";
 const string MDL_VERSION_SUFFIX_1_8 = "1_8";
+const string MDL_VERSION_SUFFIX_1_9 = "1_9";
 
 } // anonymous namespace
 
@@ -191,6 +193,27 @@ ShaderPtr MdlShaderGenerator::generate(const string& name, ElementPtr element, G
         emitLineBreak(stage);
     }
 
+    // Emit shader inputs that have been filtered during printing of the public interface
+    const string uniformPrefix = _syntax->getUniformQualifier() + " ";
+    for (ShaderGraphInputSocket* inputSocket : graph.getInputSockets())
+    {
+        if (inputSocket->getConnections().size() &&
+            (inputSocket->getType().getSemantic() == TypeDesc::SEMANTIC_SHADER ||
+             inputSocket->getType().getSemantic() == TypeDesc::SEMANTIC_CLOSURE ||
+             inputSocket->getType().getSemantic() == TypeDesc::SEMANTIC_MATERIAL))
+        {
+            const string& qualifier = inputSocket->isUniform() || inputSocket->getType() == Type::FILENAME 
+                ? uniformPrefix 
+                : EMPTY_STRING;
+            const string& type = _syntax->getTypeName(inputSocket->getType());
+
+            emitLineBegin(stage);
+            emitString(qualifier + type + " " + inputSocket->getVariable() + " = ", stage);
+            emitString(_syntax->getDefaultValue(inputSocket->getType(), true), stage);
+            emitLineEnd(stage, true);
+        }
+    }
+
     // 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);
@@ -215,6 +238,7 @@ ShaderPtr MdlShaderGenerator::generate(const string& name, ElementPtr element, G
     const string result = getUpstreamResult(outputSocket, context);
 
     const TypeDesc outputType = outputSocket->getType();
+    // Try to return some meaningful color in case the output is not a material
     if (graph.hasClassification(ShaderNode::Classification::TEXTURE))
     {
         if (outputType == Type::DISPLACEMENTSHADER)
@@ -229,7 +253,25 @@ ShaderPtr MdlShaderGenerator::generate(const string& name, ElementPtr element, G
         else
         {
             emitLine("float3 displacement__ = float3(0.0)", stage);
-            emitLine("color finalOutput__ = mk_color3(" + result + ")", stage);
+            std::string finalOutput = "mk_color3(0.0)";
+            if (outputType == Type::BOOLEAN)
+                finalOutput = result + " ? mk_color3(0.0, 1.0, 0.0) : mk_color3(1.0, 0.0, 0.0)";
+            else if (outputType == Type::INTEGER)
+                finalOutput = "mk_color3(" + result + " / 100)"; // arbitrary
+            else if (outputType == Type::FLOAT)
+                finalOutput = "mk_color3(" + result + ")";
+            else if (outputType == Type::VECTOR2)
+                finalOutput = "mk_color3(" + result + ".x, " + result + ".y, 0.0)";
+            else if (outputType == Type::VECTOR3)
+                finalOutput = "mk_color3(" + result + ")";
+            else if (outputType == Type::COLOR3)
+                finalOutput = result;
+            else if (outputType == Type::COLOR4)
+                finalOutput = result + ".rgb";
+            else if (outputType == Type::MATRIX33 || outputType == Type::MATRIX44)
+                finalOutput = "mk_color3(" + result + "[0][0], " + result + "[1][1], " + result + "[2][2])";
+
+            emitLine("color finalOutput__ = " + finalOutput, stage);
         }
 
         // End shader body
@@ -527,6 +569,13 @@ ShaderPtr MdlShaderGenerator::createShader(const string& name, ElementPtr elemen
         // and are editable by users.
         if (inputSocket->getConnections().size() && graph->isEditable(*inputSocket))
         {
+            if (inputSocket->getType().getSemantic() == TypeDesc::SEMANTIC_SHADER ||
+                inputSocket->getType().getSemantic() == TypeDesc::SEMANTIC_CLOSURE ||
+                inputSocket->getType().getSemantic() == TypeDesc::SEMANTIC_MATERIAL)
+            {
+                continue;
+            }
+
             inputs->add(inputSocket->getSelf());
         }
     }
@@ -537,7 +586,7 @@ ShaderPtr MdlShaderGenerator::createShader(const string& name, ElementPtr elemen
         outputs->add(outputSocket->getSelf());
     }
 
-    // MDL does not allow varying data connected to transmission IOR.
+    // MDL does not allow varying data connected to transmission IOR until MDL 1.9.
     // We must find all uses of transmission IOR and make sure we don't
     // have a varying connection to it. If a varying connection is found
     // we break that connection and revert to using default value on that
@@ -552,8 +601,14 @@ ShaderPtr MdlShaderGenerator::createShader(const string& name, ElementPtr elemen
     // this fix will disconnect the transmission IOR on the inside, but
     // still support the connection to reflection IOR.
     //
-    if (graph->hasClassification(ShaderNode::Classification::SHADER) ||
-        graph->hasClassification(ShaderNode::Classification::CLOSURE))
+    GenMdlOptions::MdlVersion version = getMdlVersion(context);
+    bool uniformIorRequired =
+        version == GenMdlOptions::MdlVersion::MDL_1_6 ||
+        version == GenMdlOptions::MdlVersion::MDL_1_7 ||
+        version == GenMdlOptions::MdlVersion::MDL_1_8;
+    if (uniformIorRequired && (
+        graph->hasClassification(ShaderNode::Classification::SHADER) ||
+        graph->hasClassification(ShaderNode::Classification::CLOSURE)))
     {
         // Find dependencies on transmission IOR.
         std::set<ShaderGraph*> graphsWithIorDependency;
@@ -641,10 +696,15 @@ void MdlShaderGenerator::emitShaderInputs(const DocumentPtr doc, const VariableB
     }
 }
 
-void MdlShaderGenerator::emitMdlVersionNumber(GenContext& context, ShaderStage& stage) const
+GenMdlOptions::MdlVersion MdlShaderGenerator::getMdlVersion(GenContext& context) const
 {
     GenMdlOptionsPtr options = context.getUserData<GenMdlOptions>(GenMdlOptions::GEN_CONTEXT_USER_DATA_KEY);
-    GenMdlOptions::MdlVersion version = options ? options->targetVersion : GenMdlOptions::MdlVersion::MDL_LATEST;
+    return options ? options->targetVersion : GenMdlOptions::MdlVersion::MDL_LATEST;
+}
+
+void MdlShaderGenerator::emitMdlVersionNumber(GenContext& context, ShaderStage& stage) const
+{
+    GenMdlOptions::MdlVersion version = getMdlVersion(context);
 
     emitLineBegin(stage);
     emitString("mdl ", stage);
@@ -656,30 +716,35 @@ void MdlShaderGenerator::emitMdlVersionNumber(GenContext& context, ShaderStage&
         case GenMdlOptions::MdlVersion::MDL_1_7:
             emitString(MDL_VERSION_1_7, stage);
             break;
+        case GenMdlOptions::MdlVersion::MDL_1_8:
+            emitString(MDL_VERSION_1_8, stage);
+            break;
         default:
-            // GenMdlOptions::MdlVersion::MDL_1_8
+            // GenMdlOptions::MdlVersion::MDL_1_9
             // GenMdlOptions::MdlVersion::MDL_LATEST
-            emitString(MDL_VERSION_1_8, stage);
+            emitString(MDL_VERSION_1_9, stage);
             break;
     }
     emitLineEnd(stage, true);
 }
 
+
 const string& MdlShaderGenerator::getMdlVersionFilenameSuffix(GenContext& context) const
 {
-    GenMdlOptionsPtr options = context.getUserData<GenMdlOptions>(GenMdlOptions::GEN_CONTEXT_USER_DATA_KEY);
-    GenMdlOptions::MdlVersion version = options ? options->targetVersion : GenMdlOptions::MdlVersion::MDL_LATEST;
+    GenMdlOptions::MdlVersion version = getMdlVersion(context);
 
     switch (version)
     {
         case GenMdlOptions::MdlVersion::MDL_1_6:
             return MDL_VERSION_SUFFIX_1_6;
         case GenMdlOptions::MdlVersion::MDL_1_7:
             return MDL_VERSION_SUFFIX_1_7;
+        case GenMdlOptions::MdlVersion::MDL_1_8:
+            return MDL_VERSION_SUFFIX_1_8;
         default:
-            // GenMdlOptions::MdlVersion::MDL_1_8
+            // GenMdlOptions::MdlVersion::MDL_1_9
             // GenMdlOptions::MdlVersion::MDL_LATEST
-            return MDL_VERSION_SUFFIX_1_8;
+            return MDL_VERSION_SUFFIX_1_9;
     }
 }
 

source/MaterialXGenMdl/MdlShaderGenerator.h

@@ -25,7 +25,8 @@ class MX_GENMDL_API GenMdlOptions : public GenUserData
         MDL_1_6,
         MDL_1_7,
         MDL_1_8,
-        MDL_LATEST = MDL_1_8
+        MDL_1_9,
+        MDL_LATEST = MDL_1_9
     };
 
     /// Create MDL code generator options with default values.
@@ -76,7 +77,11 @@ class MX_GENMDL_API MdlShaderGenerator : public ShaderGenerator
     /// Map of code snippets for geomprops in MDL.
     static const std::unordered_map<string, string> GEOMPROP_DEFINITIONS;
 
-    /// Add the MDL file header containing the version number of the generated module..
+    /// Get the selected MDL target language version number from the context option.
+    /// If not set, the latest version supported by GenMdl is returned.
+    GenMdlOptions::MdlVersion getMdlVersion(GenContext& context) const;
+
+    /// Add the MDL file header containing the version number of the generated module.
     void emitMdlVersionNumber(GenContext& context, ShaderStage& stage) const;
 
     /// Add the version number suffix appended to MDL modules that use versions.

source/MaterialXGenMdl/Nodes/ClosureLayerNodeMdl.cpp

@@ -16,6 +16,10 @@ MATERIALX_NAMESPACE_BEGIN
 
 const string StringConstantsMdl::TOP = "top";
 const string StringConstantsMdl::BASE = "base";
+const string StringConstantsMdl::FG = "fg";
+const string StringConstantsMdl::BG = "bg";
+const string StringConstantsMdl::MIX = "mix";
+const string StringConstantsMdl::TOP_WEIGHT = "top_weight";
 
 ShaderNodeImplPtr ClosureLayerNodeMdl::create()
 {
@@ -101,6 +105,7 @@ void ClosureLayerNodeMdl::emitFunctionCall(const ShaderNode& _node, GenContext&
 
     // Transport the base bsdf further than one layer
     ShaderNode* baseReceiverNode = top;
+    ShaderNode* mixTopWeightNode = nullptr;
     while (true)
     {
         // If the top node is again a layer, we don't want to override the base
@@ -111,6 +116,26 @@ void ClosureLayerNodeMdl::emitFunctionCall(const ShaderNode& _node, GenContext&
         }
         else
         {
+            // TODO is there a more efficient way to check if the node is a mix_bsdf?
+            std::string name = top->getImplementation().getName();
+            if (name == "IM_mix_bsdf_genmdl")
+            {
+                // handle one special case: the top node is a mix where either fg or bg is empty
+                // so basically a scale factor
+                ShaderOutput* fgOutput = top->getInput(StringConstantsMdl::FG)->getConnection();
+                ShaderOutput* bgOutput = top->getInput(StringConstantsMdl::BG)->getConnection();
+                ShaderOutput* mixOutput = top->getInput(StringConstantsMdl::MIX)->getConnection();
+                ShaderNode* fg = fgOutput ? fgOutput->getNode() : nullptr;
+                ShaderNode* bg = bgOutput ? bgOutput->getNode() : nullptr;
+                ShaderNode* mix = mixOutput ? mixOutput->getNode() : nullptr;
+                if ((fg && !bg) || (!fg && bg))
+                {
+                    baseReceiverNode = fg ? fg : bg; // take the node that is valid
+                    top = baseReceiverNode;
+                    mixTopWeightNode = mix;
+                }
+                break;
+            }
             // we stop at elemental bsdfs
             // TODO handle mix, add, and multiply
             break;
@@ -150,6 +175,11 @@ void ClosureLayerNodeMdl::emitFunctionCall(const ShaderNode& _node, GenContext&
     // base BSDF connection and output variable name from the
     // layer operator itself.
     topNodeBaseInput->makeConnection(base->getOutput());
+    if (mixTopWeightNode)
+    {
+        ShaderInput* topNodeTopWeightInput = baseReceiverNode->getInput(StringConstantsMdl::TOP_WEIGHT);
+        topNodeTopWeightInput->makeConnection(mixTopWeightNode->getOutput());
+    }
     ScopedSetVariableName setVariable(output->getVariable(), top->getOutput());
 
     // Make the call.
@@ -171,6 +201,21 @@ void LayerableNodeMdl::addInputs(ShaderNode& node, GenContext& /*context*/) cons
 {
     // Add the input to hold base layer BSDF.
     node.addInput(StringConstantsMdl::BASE, Type::BSDF);
+
+    // Set the top level weight default to 1.0
+    ShaderInput* topWeightNode = node.addInput(StringConstantsMdl::TOP_WEIGHT, Type::FLOAT);
+    ValuePtr value = TypedValue<float>::createValue(1.0f);
+    topWeightNode->setValue(value);
+}
+
+bool LayerableNodeMdl::isEditable(const ShaderInput& input) const
+{
+    if (input.getName() == StringConstantsMdl::BASE ||
+        input.getName() == StringConstantsMdl::TOP_WEIGHT)
+    {
+        return false;
+    }
+    return BASE::isEditable(input);
 }
 
 MATERIALX_NAMESPACE_END

source/MaterialXGenMdl/Nodes/ClosureLayerNodeMdl.h

@@ -23,6 +23,10 @@ class MX_GENMDL_API StringConstantsMdl
     /// String constants
     static const string TOP;  ///< layer parameter name of the top component
     static const string BASE; ///< layer parameter name of the base component
+    static const string FG;   ///< mix parameter name of the foreground
+    static const string BG;   ///< mix parameter name of the background
+    static const string MIX;  ///< mix parameter name of the amount
+    static const string TOP_WEIGHT; ///< mix amount forwarded into layer top component
 };
 
 /// Closure layer node implementation for MDL.
@@ -40,11 +44,14 @@ class MX_GENMDL_API ClosureLayerNodeMdl : public ShaderNodeImpl
 /// Note, not all elemental bsdfs support this kind of transformation.
 class MX_GENMDL_API LayerableNodeMdl : public SourceCodeNodeMdl
 {
+    using BASE = SourceCodeNodeMdl;
+
   public:
     virtual ~LayerableNodeMdl() = default;
     static ShaderNodeImplPtr create();
 
     void addInputs(ShaderNode& node, GenContext&) const override;
+    bool isEditable(const ShaderInput& input) const override;
 };
 
 MATERIALX_NAMESPACE_END