Flickering effect appears in final gathering result


Symptom
After rendering a scene using the Final Gathering render method, the flipbook (or video playback) result displays an undesirable and ugly flickering effect.


Cause
To begin with, the Final Gathering scene was rendered in a frame-based render farm setup. That is, each machine participating in the render process rendered one frame (as opposed to tile-based rendering whereby each CPU processes individual tiles). As a result of rendering the scene in a frame-based render situation, the following scenario will occur:

  1. Machine A renders frame 1
  2. Machine B renders frame 2
  3. Machine C renders frame 3
  4. When machine A has completed rendering Frame 1, it will jump to frame 4 (basically this is the same thing as using -skip in xsibatch -r). In this case, machines A,B, and C will build their respective Final Gathering map files (FGmap), as for example machine A will write the Fgmap when the rendering is completed; machine B will overwrite Machine A?s Fgmap with its FGmap, and so on and so forth... Hence the flickering effect in the final rendered result.


Solution
How to get around this problem? Essentially, the only solution for avoiding the flickering effect is as follows:

  1. Use distributed rendering, so that only one machine will read and write the FGmap file (e.g. the master machine)
  2. The Final Gathering Map-Rebuild rendering option must be set to OFF, so that when the computer will render frame 1, it will build a new Fgmap, then at frame 2, it will load the FGmap created in frame 1, compute any missing FG samples, and then write it back... So, to solve the render flickering effect with FGmap, is to make sure the FGmap contains continuous frames, so that for instance, if it renders frame 9, the FGmap contains samples for frame 1 through to frame 8.

This page was last modified 06:00, 15 Dec 2010.
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