The whole illumiRoom would just be a rear projector, and only games with built in functionality(e.g. ones that allow Kinect, 3D....special code)...would "talk" to the projector. A game with snowflakes would have elements it sends to the projector (e.g. a 2nd special HDMI output on an Xbox 720).
Not saying it's easy. It's just "extras" a game would have.