Add support for displacement in MDL generation (#1396)

Author: krohmerNV

source/MaterialXGenMdl/MdlShaderGenerator.cpp

@@ -42,7 +42,6 @@ const vector<string> DEFAULT_IMPORTS =
     "import ::anno::*",
     "import ::tex::*",
     "import ::mx::swizzle::*",
-    "import ::mx::cm::*",
     "using ::mx::core import *",
     "using ::mx::stdlib import *",
     "using ::mx::pbrlib import *",
@@ -273,9 +272,22 @@ ShaderPtr MdlShaderGenerator::generate(const string& name, ElementPtr element, G
     // Get final result
     const string result = getUpstreamResult(outputSocket, context);
 
+    const TypeDesc* outputType = outputSocket->getType();
     if (graph.hasClassification(ShaderNode::Classification::TEXTURE))
     {
-        emitLine("color finalOutput__ = mk_color3(" + result + ")", stage);
+        if (outputType == Type::DISPLACEMENTSHADER)
+        {
+            emitLine("float3 displacement__ = " + result + ".geometry.displacement", stage);
+            emitLine("color finalOutput__ = mk_color3("
+                "r: math::dot(displacement__, state::texture_tangent_u(0)),"
+                "g: math::dot(displacement__, state::texture_tangent_v(0)),"
+                "b: math::dot(displacement__, state::normal()))", stage);
+        }
+        else
+        {
+            emitLine("float3 displacement__ = float3(0.0)", stage);
+            emitLine("color finalOutput__ = mk_color3(" + result + ")", stage);
+        }
 
         // End shader body
         emitScopeEnd(stage);
@@ -289,13 +301,16 @@ ShaderPtr MdlShaderGenerator::generate(const string& name, ElementPtr element, G
             "            intensity : finalOutput__ * math::PI,\n"
             "            mode : intensity_radiant_exitance\n"
             "        )\n"
+            "    ),\n"
+            "    geometry: material_geometry(\n"
+            "       displacement : displacement__\n"
             "    )\n"
             ");";
         emitBlock(textureMaterial, FilePath(), context, stage);
     }
     else
     {
-        emitLine(_syntax->getTypeSyntax(outputSocket->getType()).getName() + " finalOutput__ = " + result, stage);
+        emitLine(_syntax->getTypeSyntax(outputType).getName() + " finalOutput__ = " + result, stage);
 
         // End shader body
         emitScopeEnd(stage);

source/MaterialXGenMdl/MdlSyntax.cpp

@@ -397,9 +397,9 @@ MdlSyntax::MdlSyntax()
     registerTypeSyntax(
         Type::DISPLACEMENTSHADER,
         std::make_shared<ScalarTypeSyntax>(
-            "float3",
-            "float3(0.0)",
-            "float3(0.0)"));
+            "material",
+            "material()",
+            "material()"));
 
     registerTypeSyntax(
         Type::LIGHTSHADER,

source/MaterialXGenMdl/Nodes/MaterialNodeMdl.cpp

@@ -46,6 +46,9 @@ void MaterialNodeMdl::emitFunctionCall(const ShaderNode& _node, GenContext& cont
         for (ShaderInput* input : node.getInputs())
         {
             shadergen.emitString(delim, stage);
+            shadergen.emitString("mxp_", stage);
+            shadergen.emitString(input->getName(), stage);
+            shadergen.emitString(": ", stage);
             shadergen.emitInput(input, context, stage);
             delim = ", ";
         }

source/MaterialXGenMdl/mdl/materialx/pbrlib.mdl

@@ -641,23 +641,33 @@ export material mx_light(
 // TODO: Check if this works in the translator and higher level nodes, like
 //       mxp_material, if not, we have to switch to the material type and 
 //       use two different names for mxp_displacemnnt.
-export float3 mx_displacement_float(
+export material mx_displacement_float(
     float mxp_displacement = 0.0,
     float mxp_scale        = 1.0
-)
-{
-    return mxp_displacement * mxp_scale * state::normal();
-}
+) [[ 
+    anno::usage( "materialx:displacementshader") 
+]] = material(
+    geometry: material_geometry(
+        displacement: mxp_displacement * mxp_scale * state::scene_units_per_meter() * state::normal()
+    )
+);
 
-export float3 mx_displacement_vector3(
+export material mx_displacement_vector3(
     float3 mxp_displacement = float3(0.0),
     float  mxp_scale        = 1.0
-)
+) [[ 
+    anno::usage( "materialx:displacementshader") 
+]] = let
 {
-    return mxp_scale * ( mxp_displacement.x * state::texture_tangent_u(0)
-                       + mxp_displacement.y * state::texture_tangent_v(0)
-                       + mxp_displacement.z * state::normal());
-}
+    float3 vec = (mxp_displacement.x * state::texture_tangent_u(0)
+                + mxp_displacement.y * state::texture_tangent_v(0)
+                + mxp_displacement.z * state::normal());
+} in material(
+    geometry: material_geometry(
+        displacement: vec * mxp_scale * state::scene_units_per_meter()
+    )
+);
+
 
 export material mx_mix_bsdf(
     material mxp_fg = material() [[ anno::usage( "materialx:bsdf") ]],

source/MaterialXGenMdl/mdl/materialx/stdlib.mdl

@@ -36,16 +36,16 @@ import ::df::*;
 // Shader Nodes
 
 export material mx_surfacematerial(
-	material mxp_surfaceshader = material() [[ anno::usage( "materialx:surfaceshader") ]],
-    float3 mxp_displacement = float3(0.0, 0.0, 0.0)
+    material mxp_surfaceshader = material() [[ anno::usage( "materialx:surfaceshader") ]],
+    material mxp_displacementshader =  material() [[ anno::usage( "materialx:displacementshader") ]]
 )
 = material(
     thin_walled: false,
     surface: mxp_surfaceshader.surface,
     backface: mxp_surfaceshader.backface,
     geometry: material_geometry(
         cutout_opacity: mxp_surfaceshader.geometry.cutout_opacity,
-        displacement : mxp_displacement,
+        displacement : mxp_displacementshader.geometry.displacement,
         normal: mxp_surfaceshader.geometry.normal
     ),
     ior: mxp_surfaceshader.ior,

source/MaterialXTest/MaterialXGenMdl/GenMdl.cpp

@@ -288,7 +288,7 @@ void MdlShaderGeneratorTester::compileSource(const std::vector<mx::FilePath>& so
         std::string iblFile = (rootPath / "resources/lights/san_giuseppe_bridge.hdr").asString();
         renderCommand += " --hdr \"" + iblFile + "\" --hdr_rotate 90";
         // set scene
-        renderCommand += " --uv_scale 0.5 1.0 --uv_offset 0.0 0.0 --uv_repeat";
+        renderCommand += " --uv_scale 0.5 1.0 --uv_offset 0.0 0.0 --uv_repeat --uv_flip";
         renderCommand += " --camera 0 0 3 0 0 0 --fov 45";
 
         // set the material