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■ Rays per FG Point
■ Interpolate Over Num. FG Points
The preset settings are defined in the text file mentalray_fg_presets.ini, found
in the \plugcfg folder in the program installation. You can modify the existing
presets and add new ones by editing this file.
Basic group
Enable Final Gather When on, the mental ray renderer uses
final gathering
on page 7782 to create global illumination or to improve its quality. Default=off.
TIP Without final gathering, global illumination can appear to be patchy. But final
gathering increases rendering time. Leave Final Gather off to preview the scene,
and then turn it on for the finished rendering. (Increasing the number of photons
used to calculate global illumination can also improve global illumination.)
Multiplier/color swatch Use these to control the intensity and color of the
indirect light accumulated by final gathering. The defaults, 1.0 and white,
produce physically correct rendering.
This is useful for adjusting the contribution of the final gather effect, thus
improving the quality of an image.
Initial FG Point Density A multiplier for the density of final gather points.
Increasing this value increases the density (and thus the quantity) of final
gather points in the image. The points will therefore be closer and more
numerous. This parameter is useful for solving geometry problems; for example,
near edges or corners. Default=1.0.
TIP When adjusting final render settings it's often helpful to visualize the final
gather points; to do so, turn on
Diagnostics on page 6129 and choose the Final
Gather option.
Rays per FG Point Sets how many rays are used to compute indirect
illumination in a final gather. Increasing this value makes global illumination
less noisy, but also increases rendering time. Default=250.
Interpolate Over Num. FG Points Controls the number of final gather points
that are used for an image sample. It is useful for solving noise problems and
getting smoother results.
For each final gather point, mental ray interpolates (averages) indirect light
values over the nearest N final gather points, with N specified by the value of
this parameter, as opposed to points within the specified radii as with the
6108 | Chapter 18 Rendering