HOWTO: Antialiasing in Mental Ray
  
PSS ID Number: Q184934
Article last modified on 04-30-1998
 
IRIX:3.7,3.71; WINNT:3.7,3.71
 
IRIX winnt
 

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The information in this article applies to:
 
 - SOFTIMAGE 3D for IRIX, versions 3.7, 3.71
 - SOFTIMAGE 3D for Windows NT, versions 3.7, 3.71
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SUMMARY
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This article offers antialiasing settings that produce the best rendering
results.
 
MORE INFORMATION
================
 
Mental ray offers an antialiasing technique that allows you to specify two
levels of antialiasing. The scene's small features are tracked and the
number of rays is automatically adapted to the appropriate level between
two values that you specify.
 
For standard-quality renders (comparable to the adaptive 2 setting in
SOFTIMAGE 3D), settings that produce the best results are -1.1 and 0.1.
 
For high-quality renders, a setting of 0.2 produces the best result. You
can use a setting of 3 or 4 if it is required, but the render time grows
accordingly.
 
A negative value allows mental ray to do under-sampling, which produces a
smoother look within the object as opposed to supersampling (which affects
the object's edge).
 
A common application of under-sampling is with motion blur. Using the
default antialiasing setting, the motion blur in mental ray does not
produce smooth results. To produce a smooth blur, set Antialiasing to
Gaussian minimum sample of -1 and maximum sample of 2. The negative value
in the minimum sample (undersampling) eliminates the grainy look inside the
blur area.
 
Try to avoid using settings with a wide range between the numbers (for
example, -1, 4). Settings such as these cause mental ray to generate
excessive buffer data and increase the memory comsumptions. Unless render
time is not an issue, use settings where the maximum difference is not
greater than 3.
 
Undersampling is not the optimal method to smooth motion blur because it
increases rendering time. You can use the -time_contrast option, which you
can add to Ray.irix5 (on IRIX) or Ray.exe on Windows NT.
 
REFERENCES
==========
 
For additional information on the -time_contrast option, please see the
following article in the Microsoft Knowledge Base:
 
   ARTICLE-ID: Q184917
   TITLE     : HOWTO: Reduce Motion Blur Calculations
 
If you have any questions concerning the information contained in this
article, contact support@softimage.com by e-mail.
 
Additional query words:
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Keywords          : kbnokeyword
Version           : IRIX:3.7,3.71; WINNT:3.7,3.71
Platform          : IRIX winnt
Issue type        : kbhowto
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Copyright Microsoft Corporation 1998.