Path tracing accumulation artifacts

Practical and theoretical implementation discussion.
MohamedSakr
Posts: 83
Joined: Thu Apr 24, 2014 2:27 am

Re: Path tracing accumulation artifacts

Post by MohamedSakr » Sun Oct 19, 2014 10:09 pm

a good RNG is C++ 11 mersenne twister , check https://github.com/SmallVCM/SmallVCM/bl ... rc/rng.hxx

ingenious
Posts: 281
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Re: Path tracing accumulation artifacts

Post by ingenious » Sun Oct 19, 2014 11:54 pm

This looks like a color quantization artifact which becomes noticeable as your image converges and the random noise disappears. You could try writing the image to some floating-point high dynamic range image format (like EXR or HDR) and play with the gamma and exposure a bit to see if the artifacts really come from the renderer or from the conversion of the pixel values to 8-bit color.
Image Click here. You'll thank me later.

citadel
Posts: 21
Joined: Fri Oct 17, 2014 4:19 am

Re: Path tracing accumulation artifacts

Post by citadel » Mon Oct 20, 2014 5:26 am

This is possibly caused by self-intersection. Solution is to offset ray origins by a small amount along the surface normal.

Brigadir
Posts: 8
Joined: Mon May 14, 2012 11:42 am

Re: Path tracing accumulation artifacts

Post by Brigadir » Mon Oct 20, 2014 9:10 pm

Ingenious, you are right, thanks a lot!
It was quantization error. I have implemented a trivial random and then floyd dithering and it solved the problem a bit. However, a perfect solution requires more efforts. Probably it is needed to port a OpenImageIO library.

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