The Cast Reflections property for RPC objects works differently than a similar setting in Autodesk® 3ds Max®. RPC content provides a specialized texture that is applied to a flat plane. When the texture is applied to the opposite side of the plane, unusual reflections can result. The Cast Reflections property for RPC content produces a more realistic result.
When you turn on Cast Reflections, the object includes a second plane that faces away from the camera. This plane shows the image of the opposite side of the RPC object. The reflection is accurate only when the RPC object is directly between the camera and the reflective surface. As the reflective surface moves to a more acute angle, the reflection thins.
When you use the Revit rendering tool, the Cast Reflections property can significantly increase memory requirements and render time. Use this property only when the RPC content should cast a reflection on a vertical surface directly behind it. RPC trees (and other plants) may not require this property turned on, even when a reflection is expected, because the front of a tree closely resembles the back.