Brash & Plucky

by: Chema Guerra

Diffraction vs. Multi-resolution

I’ve been working lately on glare/bloom/fringe and other post-processing effects in Maverick Render. Some of these inherit from our lovely ArionFX Adobe Photoshop and AfterEffects plug-in.

One complaint in ArionFX and also in Maverick is (was, because this post is about a successful fix) that Glare/Bloom diverge in shape and power when the input image is rendered at a different resolution, even if the Glare/Bloom parameters stay the same.

There are some relatively unobvious reasons for this. Basically, the challenges are:

  • Hard challenge: Diffraction is a frequency analysis effect. For a render, this happens in the discrete realm (pixels). The size (amount of pixels) of the images involved changes what frequencies and how they show up in the Fourier Transform.
  • Hard challenge: Anti-Aliasing of neighboring pixels (more prevalent at low resolution) averages their power and dims the overall Glare/Bloom overlay. This can pose a real problem for thin geometries such as lightbulb filaments.
  • Easy challenge: As illustrated in some of my previous posts, the FT itself has some properties that relate its scale and power to the scale and power of the aperture/obstacle of the lens iris. These of course must be compensated for.
  • Medium challenge: Changes in aspect ratio, or in padding in the image buffers (such as the padding between the IPR size in the UI vs. the canvas size) must be taken into account as well.

The upcoming release of Maverick will address these issues.

Here’s a small video with a sequence of Maverick post-processing effects, all rendered alternating landscape and portrait aspect ratios between 512 and 2048. The video is cropped as landscape to be easier on the eyes. As can be seen, at lower resolutions there’s always some power divergence, and a little bit of blur. But those are unavoidable to some extent.

Youtube 4K version: youtu.be/4K8F8vP76…