194 ◾ 3D Animation for the Raw Beginner Using Maya
of .6, and Glossiness of .16. Most sig-
nicantly, it is a Glossy Samples set-
ting of 8 that created the rough texture
of the ice. In Figure5.79, we see the
resulting renders, with a wood fence
during the day and a Plexiglas fence in
the evening.
Textures versus Geometry: Bump
Maps versus Displacement Maps
We have seen that there are mul-
tiple ways to make use of bit-mapped
images in Maya, including using them
directly as textures, or as the bump
map attributes of materials, or as the
color attribute of a material. As it
turns out, there is another way to use an image: as a displacement map. Like bump maps,
displacement maps do not alter the geometry of an object, but they can sometimes provide
a much more realistic simulation of geometric detail.
FIGURE 5.76 Face and EP curve.
FIGURE 5.75 Final render—a brighter face.
FIGURE 5.77 Extrude settings.
FIGURE 5.78 Rink wall.
Materials, Bump Maps, Lights, Projection versus Normal Textures ◾ 195
BUMP MAPS VERSUS
DISPLACEMENT
MAPS IN MAYA
Now, we compare the use of bump
maps and displacement maps in Maya.
Bump Maps
Bump maps simulate ne-grained
geometry by manipulating the nor-
mals information derived from a tex-
ture to create the illusion of texture on
a model.
Figure 5.80 shows a Blinn mate-
rial with a checkerboard bump map
applied to it. is was made by rst
creating a Blinn material in the
Hypershade, then creating a check-
erboard texture in the Hypershade.
With the material selected, the texture
was middle mouse button dragged to
the Bump Mapping box in the attri-
bute editor.
Displacement Maps
Figure 5.81 shows another Blinn
material, but this time, instead of using a bump map, we are using a displacement map.
We don’t do this by selecting the material itself. Rather, we go to the Hypershade and
choose the Shading Groups tab (instead of the Materials tab). We select the second
Blinn. We then create another checkerboard texture and drag it to the Displacement
Map box in the attribute editor of the Blinn Shading node.
To emphasize this distinction, Figure5.82 shows the various tabs in the Hypershade
window. e two Blinns are labeled blinn3 and blinn6, and Maya provides dierent icons
for the two of them. e rst icon gives us a hint that a bump map has been applied. e
second icon is more abstract and indicates that we are using a dierent technique, namely,
displacement mapping.
The Resulting Render: Comparing Bump Maps to Displacement Maps
Remember that the glass dish is simply a revolved curve and has completely smooth geom-
etry. Figure5.83 shows two versions ofthe polygonglass dish in the same rendering. ey
are identical geometrically. On the le, a bump map has been used to create the feeling of
detailed, striated geometry. On the right, a displacement map has been used instead.
FIGURE 5.79 (See p. CI-13 of Color Insert) Ice
rink—day and night.
196 ◾ 3D Animation for the Raw Beginner Using Maya
FIGURE 5.80 e bump map. FIGURE 5.81 e displacement map.
FIGURE 5.82 e shaders for the two glasses.
Materials, Bump Maps, Lights, Projection versus Normal Textures ◾ 197
e scaling of the textures are identical on the two glass dishes. e main dierence is
that in one, the texture serves as a bump map, and in the other it serves as a displacement
map.
e bump map creates an illusion of texture but does not give us internal shadows (shad-
ows cast by an object on itself) or the sorts of light refractions that true, geometrically thick
anddetailed glass would.
e displacement map, on the other hand, does much better. However, it too is only a
simulation, although one that demands more computational time. At the point of render-
ing, Maya has done an approximate job of computing the detailed geometry that would
have existed if the model actually had 3D surface detail in the shape of the displacement
map. We thus get a rendering that far more eectively gives the illusion of 3D geometry.
Notice the depth of detail on the dish on the right. e top of the dish gives a mottled
look to the checkerboard that is reected back to the viewer, while the one on the le
simply bends the lines in the checkerboard. And the base of the right dish looks like true
geometry, whereas the one on the le looks like there are simply dark lines drawn across
the glass. We are getting what appears to be the sort of internal shadows we expect with
true geometry.
All in all, the displacement map gives us a much richer sense of thick, cut glass.
FIGURE 5.83 (See p. CI-6 of Color Insert) Bump map versus displacement map.
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