Fix b/38321023: Hypercolor audio-reactivity

Hypercolor texcoord0.z is 10x too large.
The bug will be fixed in TB14; fix data from earlier versions.

Change-Id: Ib37cb9a3c81f7157f11cf42bf8d18352408e58c7

UnitySDK/Assets/TiltBrush/Scripts/Editor/ModelImportSettings.cs

@@ -152,6 +152,12 @@ Material OnAssignMaterialModel(Material material, Renderer renderer) {
           PerformTexcoordCoordinateConversion(desc, mesh, 0);
           PerformTexcoordCoordinateConversion(desc, mesh, 1);
         }
+        if (m_Info.tiltBrushVersion.Value.major < 14 &&
+            desc.m_Guid == new Guid("e8ef32b1-baa8-460a-9c2c-9cf8506794f5")) {
+          // Pre-TB14, Tilt Brush hadn't set the "Z is distance" semantic and texcoord0.z
+          // ended up in decimeters
+          FixupHypercolorTexcoord(desc, mesh);
+        }
 
         if (desc.m_IsParticle) {
           // Would like to do this in OnPreprocessModel, but we don't yet
@@ -214,6 +220,24 @@ static int GetUvsetSize(BrushDescriptor desc, int uvSet) {
     }
   }
 
+  void FixupHypercolorTexcoord(BrushDescriptor desc, Mesh mesh) {
+    int uvSet = 0;
+    var semantic = GetUvsetSemantic(desc, uvSet);
+    if (semantic != BrushDescriptor.Semantic.ZIsDistance ||
+        GetUvsetSize(desc, uvSet) != 3) {
+      LogWarningWithContext("Not hypercolor?");
+    }
+
+    var data = new List<Vector3>();
+    mesh.GetUVs(uvSet, data);
+    for (int i = 0; i < data.Count; ++i) {
+      Vector3 tmp = data[i];
+      tmp.z *= .1f;
+      data[i] = tmp;
+    }
+    mesh.SetUVs(uvSet, data);
+  }
+
   void PerformTexcoordCoordinateConversion(BrushDescriptor desc, Mesh mesh, int uvSet) {
     var semantic = GetUvsetSemantic(desc, uvSet);
     if (semantic == BrushDescriptor.Semantic.Vector ||