With the HIPRT backend for Cycles, rays can end up hitting the same triangle multiple times due to a issue in the spatial splitting algorithm. Most of the time this issue isn't visible, but it is quite obvious in semi-transparent shadows of meshes. So this commit adds a file that contains a object made up of many semi-transparent rectangular prisms casting a shadow onto the a plane. Ref: blender/blender#117527 Ref: blender/blender-test-data!76