Well, I usually set it up as a first person shooter. I load the gun model, create a sphere, and create a camera. I set them all to a pivot. Then, I position the gun in front of the camera, and I set the sphere below the pivot. Afterwards, I set up Sphere-to-Polygon collision detection with the sphere and plane with Collisions(), setting the response to stop. But I keep falling through the floor, no matter if I position the pivot at the origin or far away from it.