No sorry I am unable to upload the model. I suppose I complicated the question but what I am actually asking is if there is any building (even a simple office building with a flat roof) is there a way in SP to roll or drop a sphere over it and mark where the sphere collides or touches the building? Am I better off using a different modelling software? I hope this helps.

Hello. I am attempting to drop a sphere using the gravity setting in SP onto the roof of a complex structure (structure is a number of discs overlapping some higher than others and also some vertical discs sticking up from between the horizontal discs). I was wondering if there is a way of marking what points on this structure that the sphere hits or collides with? (i.e. a sort of paint over the parts it rolls over). If not then is anyone familiar with another 3D modelling software that can at least roll a sphere over a structure because in sketchup it seems the sphere can only be dragged across which is difficult to control and may not roll over certain parts of the structure. Thanks.