MaterialX v1.38.3 and MayaUSD 0.16.0 updates

doc/MaterialX.md

@@ -26,8 +26,9 @@ We currently support exporting to MaterialX-compatible UsdShade networks:
 
 ### To enable:
 
-- Rebuild the MayaUsd plugin for Maya 2022.1 or PR126 using tip of the dev branch or any commit that includes [PR 1478](https://github.com/Autodesk/maya-usd/pull/1478)
-- Look for a new "MaterialX shading" option in the `Materials` dropdown of the export options
+Two options:
+- Install MayaUSD v0.16.0
+- Rebuild tip of MayaUSD repo using a MaterialX-enabled build of USD
 
 ## Import
 
@@ -43,8 +44,9 @@ We can import MaterialX networks.
 
 ### To enable:
 
-- Rebuild the MayaUsd plugin for Maya 2022.1 or PR126 using tip of the dev branch or any commit that includes [PR 1478](https://github.com/Autodesk/maya-usd/pull/1478)
-- The import code will discover MaterialX shading networks and attempt to import them automatically
+Two options:
+- Install MayaUSD v0.16.0
+- Rebuild tip of MayaUSD repo using a MaterialX-enabled build of USD
 
 ## USD stage support in viewport
 
@@ -67,20 +69,24 @@ The same spheres exported with MaterialX shading and loaded as a USD stage: ![al
 
 ### To enable:
 
-This one is more complex and requires knowledge of how to build USD.
+Two options:
+- Install MayaUSD v0.16.0 on top of Maya 2022.3 or PR132
+- Rebuild tip of MayaUSD repo using a MaterialX-enabled build of USD and a supported Maya version
 
-**Requires Maya 2022.1 or PR126**
+Once the updated plugin is in use, the viewport will automatically select MaterialX shading over UsdPreviewSurface shading if the referenced USD stage contains MaterialX shading networks.
 
-1. Build MaterialX using the [Autodesk fork of MaterialX](https://github.com/autodesk-forks/MaterialX)
-    - Requires a version later than [PR 1285](https://github.com/autodesk-forks/MaterialX/pull/1285) for proper transparency support.
-    - Requires at minimum MATERIALX_BUILD_CONTRIB, MATERIALX_BUILD_GEN_OGSXML, and MATERIALX_BUILD_SHARED_LIBS options to be enabled
-    - We only require the OGS XML shadergen part (and USD requires the GLSL shadergen), so you can turn off all complex options like Viewer, OIIO, OSL, or Python support
-2. Install that freshly built MaterialX in the `install` location where you intend to build USD next
-3. Build a recent USD from the tip of the dev branch into the `install` location that has the updated MaterialX from step 1 (assuming you will use the build_usd.py script)
-    - There is an API change in the Autodesk branch of MaterialX that requires updating `pxr/imaging/hdSt/materialXFilter.cpp` at line 71 to remove second parameter on the `isTransparentSurface()` function call
-4. Rebuild MayaUSD plugin from the tip of the dev branch or any commit that includes both [PR 1478](https://github.com/Autodesk/maya-usd/pull/1478) and [PR 1433](https://github.com/Autodesk/maya-usd/pull/1433)
-    - Requires enabling the CMAKE_WANT_MATERIALX_BUILD option
-    - MaterialX_DIR should point to the one built in step 1
-    - PXR_USD_LOCATION should point to one built in step 3
+### Building a MaterialX-enabled USD compatible with MayaUSD
 
-Once the updated plugin is in use, the viewport will automatically select MaterialX shading over UsdPreviewSurface shading if the referenced USD stage contains MaterialX shading networks.
+We currently use MaterialX 1.38.3 and USD 20.11. Combining these two together requires patching USD:
+
+```
+git checkout tags/v21.11
+# Fetch updates selected for next USD release
+git cherry-pick 08a5644770d063fe355aff1a2069b22b84d8402a
+git cherry-pick adfc04eea92b91965b0da68503539b079a5d30d9
+git cherry-pick 4ac8a7e9a440695f0392a94e27db1683773fce76
+```
+
+Then you need to merge the pending MaterialX v1.38.3 update submitted as [pull request 1738](https://github.com/PixarAnimationStudios/USD/pull/1738)
+
+Then you build USD using the `build_usd.py` script and the `--materialx` option.

lib/mayaUsd/render/vp2RenderDelegate/material.cpp

@@ -198,7 +198,10 @@ const std::set<std::string> _mtlxTopoNodeSet = {
     // Swizzles are inlined into the codegen and affect topology.
     "swizzle",
     // Conversion nodes:
-    "convert"
+    "convert",
+    // Constants: they get inlined in the source.
+    "constant"
+
 };
 
 // clang-format on
@@ -386,6 +389,9 @@ void _AddMissingTexcoordReaders(mx::DocumentPtr& mtlxDoc)
 {
     // We expect only one node graph, but fixing them all is not an issue:
     for (mx::NodeGraphPtr nodeGraph : mtlxDoc->getNodeGraphs()) {
+        if (nodeGraph->hasSourceUri()) {
+            continue;
+        }
         // This will hold the emergency "ST" reader if one was necessary
         mx::NodePtr stReader;
         // Store nodes to delete when loop iteration is complete
@@ -422,7 +428,7 @@ void _AddMissingTexcoordReaders(mx::DocumentPtr& mtlxDoc)
                 }
             }
             // Check if it is an explicit texcoord reader:
-            if (nodeDef->getCategory() == "texcoord") {
+            if (nodeDef->getNodeString() == "texcoord") {
                 // Switch it with a geompropvalue of the same name:
                 std::string nodeName = node->getName();
                 std::string oldName = nodeName + "_toDelete";
@@ -2167,6 +2173,13 @@ void HdVP2Material::_UpdateShaderInstance(const HdMaterialNetwork& mat)
 #ifdef WANT_MATERIALX_BUILD
         const bool isMaterialXNode = _IsMaterialX(node);
         if (isMaterialXNode) {
+            mx::NodeDefPtr nodeDef
+                = _GetMaterialXData()._mtlxLibrary->getNodeDef(node.identifier.GetString());
+            if (nodeDef
+                && _mtlxTopoNodeSet.find(nodeDef->getNodeString()) != _mtlxTopoNodeSet.cend()) {
+                // A topo node does not emit editable parameters:
+                continue;
+            }
             nodeName += _nodePathMap[node.path].GetName().c_str();
             if (node.path == _surfaceShaderId) {
                 nodeName = "";