anchor.diff:                          Seq.toArray
   
                       // construct bounds and hierarchy
  -                    // TODO: 3D: sanitize incoming names. Corrupted or incompatible names cause too subtle hierarchy bugs.
  +                    // TODO: 3D: sanitize incoming names. Corrupted or incompatible names cause subtle hierarchy bugs.
                       let lights = SegmentedList.make ()
                       let surfaces = SegmentedList.make ()
                       let mutable bounds = box3Zero
  
positive.code:                                                   LightMatrixIsIdentity = transform.IsIdentity
                                                    LightMatrix = transform
                                                    LightColor = color
                                                    LightBrightness = 1.0f // TODO: 3D: see if we can figure out how to populate this.
                                                    LightIntensity = 1.0f // TODO: 3D: see if we can figure out how to populate this.
                                                    PhysicallyBasedLightType = PointLight }
                                              SegmentedList.add physicallyBasedLight lights
                                              yield PhysicallyBasedLight physicallyBasedLight
  
negative.code:         CreatePhysicallyBasedGeometry (renderable, vertexData, indexData, bounds)
  
      /// Create physically-based material from an assimp mesh. falling back on default in case of missing textures.
      let CreatePhysicallyBasedMaterial (renderable, dirPath, defaultMaterial, textureMemo, material : Assimp.Material) =
          let albedo =
              if material.HasColorDiffuse
  