wallace wrote:TRRazor wrote:Hi,
thanks for getting back with me so quickly.
That absolutely did it. I'm usually using coherence values around 0.35, since that was significantly speeding up render speeds before RTX acceleration came around.
I just set it to 0 and wasn't able to reproduce the problem. Same result with my original scene, the opacity now renders 100% transparent, instead of leaving those nasty shadows / lines.
Does that mean, however, that when using RTX, one can't use coherence?
I was using the following values in my scene (according to your questions):
1.) coherence value of 0.35
2.) 5000
3.) As mentioned above, it fixed it.
Thanks again!
Hi,
It's not coherence ratio + RTX acceleration that is causing this issue, but the combination of coherence ratio + opacity is the main cause.
This is because the random numbers are more likely to fall within the same range, so the subsequent random numbers used for surface scattering and medium scattering are inherently different for surface area on the sphere that is being occluded by the transparent torus vs the non occluded area.
This just means that you will need more samples for that difference to go away, generally the guide line is that the higher coherent ratio you use, the less variance you will have on your image, but the required sample count is also higher for you to converge to the correct image.
Thanks,
Wallace
While I was able to fix the issue in the sample scene. The same problem occured in another scene, where the coherent ratio is set to "0", so no coherent ratio at all.
Yet, the eyelashes are being rendering with a shadow, where there should be none. Please see the screenshot attached.
PS: rajib's problem, four posts above mine, is pointing towards the exact same issue. There definitely seems to be something wrong within the rendering of opacity within materials with mediums.
W10 64 bit | i7 3770K | MSI Geforce RTX 2080 (8GB) + GTX Titan Black (6GB) | 32 GB DDR3 RAM