The forms or objects that we are drawing onto that flat surface actually, in real life, have depth and dimension. As we view them and place their shapes and forms onto our drawing surface, we must always try to represent that depth so as to make the objects appear real and true. These forms must appear to extend deeply into the illusional space of our picture in order to create the only true magic in drawing and painting - the appearance of form, depth, and the natural play of light - all on a flat surface.
In order to make the task of obtaining depth and form easier, we should think about the whole object ew are drawing. Do not just look at the front visible surface, but imagine the complete object as the planes of the sides redede. Objects that have depth and breadth have backs and other sides. In order to feel this, we must study the object and draw the feeling of the complete form. If we want to draw a box, we should sketch it as if it were transparent. By drawing this way, we not only understand the box better, but are more likely to draw it correctly in size and shape. We certainly will be able to protray the illusion of depth far easier this way than if we just concentrated on the visible surface.
Objects appear very different when viewed from various positions. Because of this, we must establish our viewing point (the position from which we view the subject) and stick with it for the complete picture. When we observe our subject, we see depth and three demensions. When we draw this subject onto our flat surface as it appears to the eye, we are then DRAWING IN PERSPECTIVE.