DWAB Compression Artifacts

[vermakov]

Hi,

I'm currently experimenting with DWAB compression settings in V-Ray and I've ran into some problems when I take those renders to comp.

For this test, I've rendered four sets of images. 2 diffuse and 2 lighting pass. One set is rendered with Zip compression and the other set is rendered with DWAB compression set to 45.0. When I bring the DWAB images into my compositing software and divide the lighting by diffuse I get strange artifacts around the edges. I've also noticed these artifacts show up in very dark area of some renders too. The Zip compression showed no sign of these artifacts. Is there a workflow to mitigate or remove these artifacts through V-Ray?

Cheers

[vermakov]

Bump post. Anyone?

[yolov]

Those seem like artifacts from the compression. DWAA and DWAB are lossy compression methods. I tried the same scenario and there are many pixels with odd pixel values, so any operations like multiply and divide will inevitably result in visible artifacts.
A workaround would be to clamp the values, especially where there's very small negative values to something just after zero, for example clamp min = 0.001.
Or avoid using DWAa/b if possible.