It's impossible to draw true 3-D on a flat surface, but by using perspective and shading you can portray a convincing illusion. Creating perspective involves the use of the vanishing point and an understanding of contours. Proper shading via placement of light sources adds depth to the drawing.
- Determine the perspective of the drawing
Start by determining how far above or below the viewer the subject is intended to be. This will determine where to position the point of view. Horizon is by default at the viewer's eye level. Lowering the horizon makes the subject look larger, and raising it makes it look smaller.
- Draw lines of action and contour
When drawing a subject intended to be portrayed as moving, draw the center line of action. Then, draw light guidelines that wrap around the subject as though it were a 3-D figure. Getting it exactly right isn't important in the sketching stage.
- Find the light source
After determining from which angle the subject will be illuminated, you can know where shading will likely occur. If a light source is closer to the subject, it will create more noticeable contrasts of light and shadow.
- Draw smaller details
Draw the small details of the subject, such as facial features or clothing. Be mindful of the lines of contour, and try to follow them. Shade where necessary.