Shaders and Texturing - An Introduction to Computer Graphics for Artists - page 186

An improperly calibrated monitor can result in poor quality images. For example,
on the videogame Full Spectrum Warrior , a programmer decided to test textures on
an improperly calibrated monitor. He did this with the idea that if the textures looked
right on that monitor they would look better on properly calibrated monitors because
a good monitor produces better results than a bad monitor. The problem is that this
theory couldn't possibly work. If you calibrate your art to a poorly calibrated moni-
tor, it will only look good on monitors calibrated the same way. If all monitors are
calibrated to the same standard, or an attempt is made to do so, then the results
should fall within a predictable and acceptable range. On Full Spectrum Warrior ,
the results of the test led the programmer to modify the textures so that they would
look right on his test monitor. Once he had done this, they looked wrong on every
other monitor in the studio.
Monitor calibration is a must for any studio or artist that intends to produce con-
sistent aesthetically appealing color.

11.5.3 Photo Maps

The most common texture channel used is for color. Photo-based textures are some-
times used as color maps instead of hand-painted maps because of the detail they
offer. The type of problems associated with failure to think of textures as informa-
tion is illustrated well in photo textures.
Photographs record the end result of a myriad of interactions that affect how light
travels within a scene. Because they do not measure the color of objects, but refl ected
color based on numerous variables other than and including the diffuse color of the
object, the colors can be incorrect and polluted with considerable channel interfer-
ence. The fi rst step towards extracting the information you need from a photograph
is to learn to recognize the type of information it does contain, and how to separate
it into different channels so that you can clean it up.

11.5.3.1 Perspective/Lens Distortion

The shape of your lens will cause straight lines to bend as if curved unless it is a
very long lens (400 mm or longer). The shorter your lens length is, the greater the
distortion will be. Most cameras are sold with a 50 mm lens. This lens length is
short enough to cause moderate distortion when photographing subjects at a dis-
tance. This is the fi rst channel of information that must be fi xed if you intend to
make texture maps from the photo. To do this, some photo-editing applications have
perspective correction tools (Fig. 11.5 ). Depending on how much distortion there is,
this may be accomplished quickly, or only with some effort.
To improve the odds of acquiring a usable image, care should be taken at the time
the photograph is made to align the camera at a perpendicular angle to your subject,
with its sides parallel to the edges of your image plane. The longer your lens is, the