Using get value producing attrs when checking texture assets in NormalMapTextureChecker

pxr/usd/bin/usdchecker/CMakeLists.txt

@@ -144,3 +144,13 @@ pxr_register_test(testUsdChecker12
     EXPECTED_RETURN_CODE 1
 )
 
+pxr_install_test_dir(
+    SRC testenv/testUsdChecker
+    DEST testUsdChecker13
+)
+
+pxr_register_test(testUsdChecker13
+    PYTHON
+    COMMAND "${CMAKE_INSTALL_PREFIX}/bin/usdchecker clean/cleanNormalMapReader.usda"
+    EXPECTED_RETURN_CODE 0
+)

pxr/usd/bin/usdchecker/testenv/testUsdChecker/clean/cleanNormalMapReader.usda

@@ -35,5 +35,34 @@ def "World"
             normal3f inputs:normal.connect = </World/material/NormalMap.outputs:rgb>
         }
     }
-}
 
+    # Normal map compliance checker should handle connected asset attributes.
+    def Material "assetOnMaterial"
+    {
+        asset inputs:file = @texture.jpg@
+
+        def Shader "ColorMap"
+        {
+            uniform token info:id = "UsdUVTexture"
+            asset inputs:file.connect = </World/assetOnMaterial.inputs:file>
+            float3 outputs:rgb
+        }
+
+        def Shader "NormalMap"
+        {
+            uniform token info:id = "UsdUVTexture"
+            token inputs:sourceColorSpace = "raw"
+            float4 inputs:scale = (2.0, 2.0, 2.0, 1.0)
+            float4 inputs:bias = (-1.0, -1.0, -1.0, 0.0)
+            asset inputs:file.connect = </World/assetOnMaterial.inputs:file>
+            float3 outputs:rgb
+        }
+
+        def Shader "Surface"
+        {
+            uniform token info:id = "UsdPreviewSurface"
+            color3f inputs:diffuseColor.connect = </World/assetOnMaterial/ColorMap.outputs:rgb>
+            normal3f inputs:normal.connect = </World/assetOnMaterial/NormalMap.outputs:rgb>
+        }
+    }
+}

pxr/usd/usdUtils/complianceChecker.py

@@ -458,13 +458,21 @@ def _TextureIs8Bit(self, asset):
         ext = Ar.GetResolver().GetExtension(asset.resolvedPath)
         # not an exhaustive list, but ones we typically can read
         return ext in ["bmp", "tga", "jpg", "jpeg", "png", "tif"]
-        
+
     def _GetInputValue(self, shader, inputName):
-        from pxr import Usd
+        from pxr import Usd, UsdShade
         input = shader.GetInput(inputName)
         if not input:
             return None
-        return input.Get(Usd.TimeCode.EarliestTime())
+        # Query value producing attributes for input values.
+        # This has to be a length of 1, otherwise no attribute is producing a value.
+        valueProducingAttrs = UsdShade.Utils.GetValueProducingAttributes(input)
+        if not valueProducingAttrs or len(valueProducingAttrs) != 1:
+            return None
+        # We require an input parameter producing the value.
+        if not UsdShade.Input.IsInput(valueProducingAttrs[0]):
+            return None
+        return valueProducingAttrs[0].Get(Usd.TimeCode.EarliestTime())
 
     def CheckPrim(self, prim):
         from pxr import UsdShade, Gf