Shaders and Texturing - An Introduction to Computer Graphics for Artists - page 187

Fig. 11.5 The image on the left is an unadjusted photo that contains lens distortion. On right , it
has been straightened out in a photo editing program but is missing corner detail due to the original
distortion

less distortion you will have, but it will also require you to be farther from the
subject. Another solution is to use a multi-plane camera. This type of camera is very
expensive, but if you have access to one, you will be able to photograph a subject
from a near distance with almost no distortion at all.

11.5.3.2 Shadows

The stronger your light is, the stronger the shadows in your photo will be. The most
prominent shadows will be cast shadows that are cast by nearby objects. These will
be hard edged in strong light, and will cover parts of the objects they are cast upon.
These must be removed entirely from your photo if it is to be usable in a cg environ-
ment as a texture. You do not want shadows cast by a light source that doesn't exist
in your scene, or based on an object that also doesn't exist in your scene.
Another type of shadow, but one that is often allowed to remain in textures
because it is so diffi cult to remove, are the fi ne shadows on the surface of an object
caused by slight irregularities (Fig. 11.6 ). Wood grain, plaster walls, small pits in
bricks, drips of paint on a painted wall, and many other things are good examples of
this type of shadow. If you have the time and can paint them out, it is best to do so.
Before you do, however, you may want to fi rst trace off their shape into another
layer as a guide for making a bump map.

11.5.3.3 Contrast

Contrast is the degree of difference between colors and tones in an image. If con-
trast is weak, individual colors are more diffi cult to see. If contrast is strong, color