Add support for ORM maps in mujoco file format plugin

The ORM texture is a packed-channel map, with ambient occlusion in Red, roughness in Green, and metallic in Blue channel.

PiperOrigin-RevId: 772367369
Change-Id: I88a4dee2477daa1e3c0b00197bfbe2b276ba9937

test/experimental/usd/plugins/mjcf/mjcf_file_format_test.cc

@@ -161,6 +161,7 @@ TEST_F(MjcfSdfFileFormatPluginTest, TestMaterials) {
   EXPECT_PRIM_VALID(stage, "/mesh_test/Materials/material_layered");
   EXPECT_PRIM_VALID(stage, "/mesh_test/Materials/material_layered/uvmap");
   EXPECT_PRIM_VALID(stage, "/mesh_test/Materials/material_layered/diffuse");
+
   EXPECT_PRIM_VALID(stage, "/mesh_test/Materials/material_layered/normal");
   ExpectAttributeHasConnection(
     stage,
@@ -170,6 +171,33 @@ TEST_F(MjcfSdfFileFormatPluginTest, TestMaterials) {
   ExpectAttributeEqual(
     stage, "/mesh_test/Materials/material_layered/normal.inputs:file",
     pxr::SdfAssetPath("textures/normal.png"));
+
+  EXPECT_PRIM_VALID(stage, "/mesh_test/Materials/material_layered/orm_packed");
+  ExpectAttributeHasConnection(
+    stage,
+    "/mesh_test/Materials/material_layered/"
+    "PreviewSurface.inputs:occlusion",
+    "/mesh_test/Materials/material_layered/orm_packed.outputs:r");
+  ExpectAttributeHasConnection(
+    stage,
+    "/mesh_test/Materials/material_layered/"
+    "PreviewSurface.inputs:roughness",
+    "/mesh_test/Materials/material_layered/orm_packed.outputs:g");
+  ExpectAttributeHasConnection(
+    stage,
+    "/mesh_test/Materials/material_layered/"
+    "PreviewSurface.inputs:metallic",
+    "/mesh_test/Materials/material_layered/orm_packed.outputs:b");
+  ExpectAttributeEqual(
+    stage, "/mesh_test/Materials/material_layered/orm_packed.inputs:file",
+    pxr::SdfAssetPath("textures/orm.png"));
+
+  EXPECT_PRIM_VALID(stage, "/mesh_test/Materials/material_metallic");
+  EXPECT_PRIM_VALID(stage,
+                    "/mesh_test/Materials/material_metallic/PreviewSurface");
+  ExpectAttributeEqual(stage,
+    "/mesh_test/Materials/material_metallic/PreviewSurface.inputs:metallic",
+    0.6f);
 }
 
 TEST_F(MjcfSdfFileFormatPluginTest, TestGeomRgba) {

test/experimental/usd/plugins/mjcf/testdata/materials.xml

@@ -2,11 +2,14 @@
   <asset>
     <texture name="diffuse_tex" file="textures/cube.png" type="2d" />
     <texture name="normal_tex" file="textures/normal.png" type="2d" />
+    <texture name="orm_tex" file="textures/orm.png" type="2d" />
     <material name="material_red" rgba="0.8 0 0 1" />
     <material name="material_texture" texture="diffuse_tex" />
+    <material name="material_metallic" rgba="0.8 0 0 1" metallic="0.6"/>
     <material name="material_layered">
       <layer texture="diffuse_tex" role="rgb"/>
       <layer texture="normal_tex" role="normal"/>
+      <layer texture="orm_tex" role="orm"/>
     </material>
     2d texture="diffuse" normal="normal" />
     <mesh name="tetrahedron" vertex="0 0 0  1 0 0  0 1 0  0 0 1"/>