What are the rules in sketching?
I finally found it. =)
Objects appear smaller as they move back away from your eye and equally objects drawn larger appear closer!
Lines and surfaces are their largest closest to the picture plane.
Lines or edges that are parallel appear to meet as they recede from the picture plane.
All vertical lines are parallel when using one point perspective (the viewer is not looking up or down at the objects)
Objects drawn in front of one another appear closer (overlapping!)
Images further away will appear lighter, with less contrast and detail.
Perspective’ by Scott E. 'Sven' Johnson