MaterialX: Two small issues with boolean inputs

[JGamache-autodesk]

Description of Issue

We found two issues with boolean inputs while developing MaterialX node definitions for use with USD

• Default values are not copied to SdrNode inputs. Boolean is not a Sdr type, but is recognized as a Sdf one, so the fix is to add a check where the boolean type is handled by the parser:

            type = converted.valueTypeName.GetAsToken();
+            if (type == SdfValueTypeNames->Bool) {
+                defaultValue = UsdMtlxGetUsdValue(element, isOutput);
+            }

• Truth values are inversed when explicitly set. Can be fixed by swapping "true" and "false" in hdMtlx.

Steps to Reproduce

1. Extract the attached MaterialX node definition file boolean_nodedef.zip in a location that will be read by MaterialX/USD (either in the MaterialX install, or in a location read via the PXR_MTLX_STDLIB_SEARCH_PATHS env var).
2. Load the boolean_nodedef_defaultvalue.usda from these bundled scenes boolean_nodedef_scenes.zip and notice the capsule is green. It should be red because the default value of use1 is true.
3. Load the boolean_nodedef_explicit.usda scene from the scene bundle and notice the capsule is red. It should be green since we explicitly set use1 to 0.

System Information (OS, Hardware)

Package Versions

Build Flags

[tallytalwar]

Thanks @JGamache-autodesk for catching this.

For the first issue you found regarding Boolean not being a Sdr type and checking for SdfValueTypeNames->Bool could you do the following instead:

             type = converted.valueTypeName.GetAsToken();
+           // Do not use GetAsToken for comparison as recommended in the API
+           if (converted.valueTypeName == SdfValueTypeNames->Bool) {
+                defaultValue = UsdMtlxGetUsdValue(element, isOutput);
+                metadata.emplace(SdrPropertyMetadata->SdrUsdDefinitionType, 
+                          converted.valueTypeName.GetType().GetTypeName())
+           }

Without adding the sdrUsdDefinitionType metadata, a call to GetDefaultValueAsSdfType will incorrectly return the default of the Bool type, which is True.

Refer https://github.com/PixarAnimationStudios/USD/blob/release/pxr/usd/sdr/shaderProperty.cpp#L536-L542 and https://github.com/PixarAnimationStudios/USD/blob/release/pxr/usd/sdr/shaderProperty.cpp#L619 for more details.

A similar thing was recently done for UsdShadeShaderDef: 409b6e9

Please feel free to submit a PR with the fix and please include a test exhibiting this behavior.

Thanks

[jilliene]

Filed as internal issue #USD-7242

[JGamache-autodesk]

Hi @tallytalwar , thanks for the pre-review. The PR has been submitted.

[JGamache-autodesk]

PR has been accepted. Closing issue. Thanks!