9

Bump Mapping 1507
Bumpmappingusestheintensityofthemapto
affectthesurfaceofthematerial.Inthiscase,the
intensity affects the apparent bumpiness of t he
surface: white areas protrude, and black areas
recede.
Use bump maps when you want to take the
smoothness off a surface, or to create an embossed
look. Keep in mind, however, that the depth effect
of a bump map is limited. If you want extreme
depth in a surface, you should use modeling
techniques instead. For example, the Displace
modifier (page 1–629) pushes surfaces or faces in
andoutbasedontheintensityofabitmapimage.
(Displacement mapping (page 2–1511) is another
way to do emboss a surface.)
Grayscaleimagescanmakeeffectivebumpmaps.
Maps that shade between white and black generally
work better than maps with hard edges b etween
the w hite and black areas.
The bump map Amount adjusts the degree of
bumpiness. Higher values render as higher relief;
lowvaluesrenderaslowrelief.
Thebumpsareasimulationcreatedbyperturbing
face normals before the object is rendered. Bec ause
of this, bumps don’t appear on the silhouette of
bump-mapped objects.
Tip: If you render a bump-mapped material and
notice aliasing in the highlights, try turning on
supersampling (page 2–1459) and rendering again.
Note: Most controls on the Output rollout (page
2–1621) don’taffectbumpmapping. Onlythe
Invert toggle is considered; it reverses the direction
of the bumps.
Procedure
To assign a bump map:
1.
Click the Map button labeled Bump.
The Material/Map Browser (page 2–1412) is
displayed.
2. Cho ose from the list of map types (page
2–1617),andthenclickOK.
TheMaterialEditorisnowatthemaplevel,and
displays controls for the map parameters.
(If you choose Bitmap as the map ty pe, you first
see a file dia lo g that lets you cho ose the image
file.)
3. Usethemapcontrolstosetupthemap.
Tip: To avoid aliasing caused by a 2D bump
map, go to the bump map’s C o ordinates
rollout.SetBlurtobeintherange0.3to0.6,
and increase Blur Offset to b e greater than 0.0.
The default Blur and Blur Offset values work
well for mapping other material components,
but for bump mapping, lower Blur and higher
Blur Offset values give better results.
To remove a bump map from a materia l:
Tip:
You can disable the map without removing it.
Simply turn off the toggle immediately to the left
of the map button on the Special Effects rollout.
1. If the Material Editor is displaying the map
controls, click the Ty pe button (page 2–1449)
to display the Material/Map Browser. If the
mapcontrolsaren’tvisible,clicktheBumpmap
button to display them, and then click the Type
button.
2. In the Browser, choose NONE as the m ap ty pe,
and then click OK.
The map is removed.