9

Displacement Mapping 1511
To a ssign a bitmap as a refraction map:
1.
In the Maps rollout, click the Refraction map
button.
2. Use the Material/Map Browser (page 2–1447) to
choose the Bitmap type.
3. Use the file dialog to choose the bitmap file.
For bitmapped refractions, you don’t
necessarily want to reduce the map strength.
Dis pla cement M appi ng
Material Editor > Standard material > Maps rollout >
Displacement button
Using displacement mapping to alter a surface
A displacement map displaces the geometry of
surface s. The effect is similar to using the Displace
(page 1–629) modifier. Unlike bump mapping
(page 2–1506), displacement mapping actually
changes the geometry of the surface or patch
tessellation. Displacement maps apply the g r ay
scale of the map to generate the displacement.
Lighter colors in the 2D image push outward more
strongly than darker colors, resulting in a 3D
displacement of the geometry.
Wa rning: A displacement map generates many
triangular faces per surface, sometimes over 1 M faces
per surface. While displacement mapping can create
good effects, there is a large cost in terms of time and
memory.
The displacement Amount is measured as a
percent a ge of the diagonal of the bounding box for
the object that contains the patch or surface. This
makes the displacement effect consistent for all
surfaces in an object, and it als o means that w hen
you scale the object, the displacement is scaled
with it.
Yo u c a n a p p l y a d i s p l a c e m e n t m a p d i r e c t l y t o t h e
following kinds of objects:
• Bezier patches (page 1–993)
• Editable meshes (page 1–996)
• Editable polymeshes (page 1–1022)
• NURBS surfaces (page 1–1078)
For other kinds of geometry such as primitives,
extended primitives, compound objects, and so
on, you can’t apply displacement mapping directly.
To use displacement mapping with these kinds
of objects, apply a Disp Approx (page 1–628)
(Displacement Approximation) modifier. This
makes the object’s surface displaceable. Disp
Approx works with a ny kind of object that you can
convert to an editable mesh.
Displacement mapping isn’t visible in viewports
unless you apply a modifier to make it so.
•ForNURBSsurfaces,youcanmake
displacement mapping visible in viewports and
editable as a m esh object by using the Displace
NURBS (page 1–515) world space modifier.
• For editable meshes and objects with Disp
Approx applied to them, use the Displace Mesh
(page 1–514) modifiertoobtainthesameeffect.
Note: If you apply a UVW Map (page 1–922)
modifier to the surface, all maps obt ain their
coordinates from the modifier except for the
displacement map, which always obtains its
coordinates from the original surface or the
Disp Approx modifier.
Under certain circumstances, such as when the
underlying mesh is fairly simple, displacement