Bump maps are grayscale textures you map to objects
to create the illusion of surface relief (elevations and depressions)
on an otherwise flat object.
With bumps maps depressions
and elevations look real, but are not, because they don’t alter
the geometry of the surface the way
Displacement maps do. Bump
maps just change the direction of the surface’s normals based on
the bump map’s Alpha Gain value.
Use
bump maps to create very shallow reliefs. For example, you can make objects
look like they are embossed, have shallow rolling hills, and so
on.
Because bump maps are
not true surface relief, they:
- cannot cast or receive shadows
- cannot be seen if you silhouette the
mapped object
- take less time to render than displacement
maps
NoteFile textures that
are used for bump mapping are usually connected via their
outAlpha attribute.
If the corresponding texture image file does not provide an alpha
channel, then the bump effect may be missing when using certain
image formats.
To avoid this, turn on
the Alpha is Luminance attribute
in the Color Balance section of the File
Texture node. For more information, see
File.
Related topics
-
About surface relief
-
Texture mapping
-
Map a 2D or 3D texture
Tip
- Map surface relief (bumps or displacements)
to the Blinn surface material to reduce
highlight roping or flickering. The soft highlights on Blinn surfaces
are less likely to cause roping or flickering than the harder highlights on Phong surfaces.
- Although scratches are like little depressions,
you can more easily achieve them with 2D texture.
