Shaders and Texturing - An Introduction to Computer Graphics for Artists - page 193

Fig. 11.12 This image has a strong blue hue shift and refl ected yellow light from the left side of
the image

you will see an orange tinge to the fur nearest the pail, and a dark patch on the pail
beside the bear, even if shadows are being cast in the opposite direction.
It is good to be aware of this so that in those situations when refl ected light
noticeably changes the colors in your texture map, you can remove it by editing.

11.5.3.9 Specularity

Photographs of objects that are wet might have good saturation because the water
dilutes any dirt that is on the object, but it also causes specular highlights to be
baked into the map (Fig. 11.13 ). For the same reason that the shape of shadows in a
photo does not match height information needed in a bump map (see Sect. 11.5.4.3 ),
refl ected highlights in a photo will not match the shape or intensity of specular val-
ues that should be painted into a specularity map.

11.5.3.10 Refl ections

A refl ection error is a full refl ection of something in your scene, usually in a hard
polished surface, and it must be removed or your map will not make sense
(Fig. 11.14 ). There is a narrow exception to this. When you want refl ections in your
scene but cannot build the refl ected object in 3D, you may want to photograph the
refl ection into your textures. However, if you do this, it is better to shoot the refl ected
object itself and add it to your shader as a refl ection map rather than include a photo