8

1034 Glossary
two m ethods of pixel averaging. Only one can be
active at a time.
Both methods require approximately the same
rendering time. Summed-area filtering generally
yields superior results but requires much more
memory. Pyram idal filtering requires the progra m
to allocate memory equal to appro ximately
133% of the size of the bitmap. By comparison,
summed-area fi ltering requires the program to
allocate approximately 400% of the size of the
bitmap.
Use summed-area filtering only for smaller
bitmaps, and avoid using any more such bitmaps
in a scene than necessary.
Pyramidal filtering is quite adequate for most
purposes. However, because it applies filtering as a
funct ion of distance, irregular antialiasing mig ht
occur on detailed texture maps that are applied
to a plane receding into the distance. The effect
of pyramidal filtering on extreme perspectives
such as this is even more noticeable in animations,
where portions of the texture map appear to
"sw im." If this occurs, turn on summed-area
filtering for the material.
Note: To control whether or not a background
image is affected by the renderer’s antialiasing
filter, choose Customize > Preferences >
Rendering
(page 3–863)
andthenturnonFilterBackground
in the Ba ckground Antialiasing group.
Filtering (Character Animation)
Filtering is the action of using selec ted data, rather
than all data.
In the
Motion Mixer (page 2–581) ,youusethe
trackgroup (page 3–1118) filter to select the biped
parts that will be affected by motion clips and
transitionsontrackswithinthetrackgroup. See
Filtering Mixer Tracks (page 2–589) .
Filteringisalsoa
motion-capture technique (p age
2–910)
. Motion-capture and marker data typically
have keys at every frame. Filtering motion-capture
data reduces the number of keys, making the
job of altering or personalizing the motion data
simpler. Other filtering options include footstep
extraction, apply ing the skeletal structure stored
inthemotion-capturefiletothebiped,loopingthe
data, importing a portion of the motion capture
file, and select ing tracks to load. See
Filtering
Motion-Capture and Marker Data (page 2–912)
.
Final G ather ing (mental ray
R enderer )
Final gathering is an optional, additional step to
calculating
global illumination (p age 3–92) .Using
a photon map to calculate global illumination can
cause rendering artifacts such as dark corners and
low-frequency variations in the lighting. You can
reduce or eliminate these artifacts by turning on
final gathering, w hich increases the number of rays
used to calculate global illumination.
Scene rendered with global illumination but no final gather