What is high quality pixel filtering?


This option is available in Corona Renderer 4 and newer and it improves rendering speed (or equivalently, reduces noise and improves antialiasing). It is exactly equivalent to the existing "Tent" filter with width 2.0 in the sense that they will converge to exactly the same image.



How to enable it? 


In Corona Renderer 4 and newer the high quality filtering is enabled by default for all new scenes. 

When opening older scenes, it is left disabled to guarantee consistency with previous renders. It can be optionally enabled.


"Use high quality filtering" option can be found in Render Setup > System > Frame Buffer > Image filter




Disabling the "Use high quality filtering" option will result in switching to the legacy Tent filtering, which will usually make the rendering slower and more noisy.




Examples


1. Fine textures


Old method:


Crop:

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Full image:

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New method:


Crop:

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Full image:

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[Click here for an interactive comparison]


Note that the differences are subtle, however:

  • The pattern visible on the fabric in darker (more noisy) areas is easier to see with the new filtering method.
  • There is generally less perceivable noise with the new filtering method.
  • Some areas are not affected at all (where there are sharp edges and no visible noise).



2. GI noise and depth of field


Old method:


Crop:

(click to open in new tab)


Full image:

(Click to open in new tab and enlarge)



New method:


Crop:

(click to open in new tab)


Full image:

(Click to open in new tab and enlarge)


[Click here for an interactive comparison]


The differences are again subtle, but can be seen in:

  • The darkest places where the GI noise is mostly visible. Note that with the new method, the noise is "softer" and generally appears more natural to the eye.
  • Bright highlights are softer and look more natural (the right side of the railing at the top-center of the image, close to the bright balcony door).
  • Areas heavily affected by depth of field are softer and less noisy.
  • Some areas are not affected at all (where there are sharp edges and no visible noise).




Limitations


Currently, one limitation which we would like to remove, is that only the Corona High Quality denoiser works with high quality pixel filtering. The AI denoisers (neither NVIDIA nor Intel) cannot be used with high quality filtering. 

See: Error message: Using high quality pixel filtering with AI denoising is not supported.