matte self-shadowing

im doing a photo montage. and i need the matte geometry ( surrounding buildings and road) to cast shadows on the main building geometry.. but not on each other (that would give double shadows in montage, as these shadows are already present in the photo) . however i do wish the matte geometry to receive shadows from the main building, otherwise there would be no point in having a matte in the first place!

basically need a “disable self shadowing” option for the matte system, or shadowcasting to be added to the “trace sets” system.

any clever workaround..?

Could you send us a test scene with some screenshots as an examples to support@chaosgroup.com so we try to wind a possible workaround.