8

144 Chapter 17: Rendering
With DirectX 8, you can v iew a normals map
in shaded viewpor ts by u sing the
Metal Bump
Direct3D viewport shader (page 2–1424)
.
With DirectX 9, you can view a normals map in
any shaded viewp ort.
Component Options (Selected Elements Unique
Settings)
Therearetwouniquesettingsforanormalsmap:
Output into Normal Bump—When on, assigns a
Normal Bump map to the Target Map Slot, and
places the rendered Normal Bump map in the
Normal component of the
Normal Bump map
(page 2–1541)
. Default=off.
Render Height Ma p into Alpha Channel —When on,
renders a g r ayscale height map and assigns it to
the alpha channel of the Normal map. If you are
rendering to a fi le type that doesn’ t have an alpha
channel, this setting has no effect. Default=off.
Height Map
A height map is a grayscale map that stores the
relative height of the source object when you
render with normal projec t ion. (See
Creating and
Using Normal Bump Maps (page 3–146)
.) You
can use the height map as a displacem ent map on
the target object. This is a way to add detail to the
edges of the low-resolution object, because edges
are not affected by the normal bump map itself.
Note: When using a height map as a displacement
map with the mental ray renderer, be sure to
use the
Height Map Displacement shader (page
2–1532)
.Also,turnoffSmoothing,either
globally or for the individual object on the Object
Properties dialog >
mental ray panel (p age 1–121) .
In addition, when rendering with mental ray,
if you’re applying the height map to a standard
material, apply the map as a Displacement map on
the
mental r ay Connection rollout (page 2 –1305)
(unlock the m ap first), not on the Maps rollout.
Tip: Using a paint program such as Adobe
Photoshop on a height map is possible, but prone
to error. The values in t he height map depend
on the shapes of both the low-resolution and
high-resolution models, and it’s easy to damage
the mathematical accuracy. If you p aint any
changes onto the map, be careful to preserve the
facetedlook,andavoidthetemptationtoblur
away the facets. You might try painting in Additive
or Subtractive mode, to add to or subtract from
the d isplacement, be cause Normal mode wil l set a
fixed displacement, making it difficult for an ar tist
to control the result.
Component Options (Selec ted Elements Unique
Settings)
There are no unique sett ings for a height map.
Blend Map
A blend map is like a complete map, except that all
its components, not just shadows, are optional.
Component Options (Selec ted Elements Unique
Settings)
For a blend map, you can choose not to render any
of the following components:
•Lighting
•Diffusecolor
• Specular color
•Reflections
•Shadows
•Ambientcolor
•Self-illuminationcolor
•Refractions
Alpha Map
An alpha map saves only the alpha channel of the
rendered object.