Well, 3dnickel, I think learning about UVmapper is LOT easier than trying to calculate "three 'physical' variables: the distance of the camera to the object (in pu's), the camera's focal length (in mm)and the size of the final render (in pixels)." ;) It is the UV Mapping that determines how the texture is applied to your object, not the dimensions, shape, scale, etc. If there are no UV Mapping coordinates applied to the object, the texture just gets stretched or squshed in an arbitrary fashion and the results can be very unpredictable. The program called UVMapper allows you to actually see how the texture is being applied. Without this "texture template" you are working blind.