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Pipeline and trouble shooting

June 17, 2014

The final render of the fruit bowl used both FG and GI indirect lighting systems. Most of the rendering issues that I encountered were solved by tweaking both of these systems.

In the final fruit bowl render the following issues were encountered:

  • Lengthy render times
  • Splotch marks in render
  • Grain/noise
  • Over exposed SSS of grapes

The long render times were reduced by using FG with GI so that the GI global illum photons could be reduced. The illum photons were at 300,000 when FG was not enabled. Once FG was turned on, the amount of illum photons needed decreased significantly resulting in a faster render.

The splotchy marks were also a problem in my renders. Most of these issues were removed once I increased my FG filterning quality 1. However to fix the rest of the splotchy marks, the unified sampling was increased to 1.

I also encountered grain in my renders which were not fixed by turning unified sampling to 1. Instead of brute forcing unified sampling, I increased the FG accuracy to around 250 which seemed to fix the problem.

The sub surface scattering of the grapes had some exposure issues with lights causing the misss fast shader to be over exposed and look white/grey. This issue wasn’t fixed entirely, however the over exposed effect was reduced by lowering the intensity of the backlight behind the grapes. Additionally, the shader colors of the grapes had their values decreased to make them darker.

In order to be consistent with the rendering pipeline, there were various things that had to be set. This included:

  • Checking that the normals were positive
  • Checking and fixing UV maps for objects
  • Following linear workflow by turning on color management and setting lights to quadratic
  • Checking the scene scale
  • Start to light the scene with everything assigned a default mia material with no reflectivity
  • Multiplying light intensities by either 12.6 or 3.15 depending on what light is used to get the correct photon intensity for GI
  • Diagnosing photon maps

 

 

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