artefacts in edges to bright objects

[max.m]

i have the problem that i can´t get rid of this artefacts in the edges of the facade. i face the same problem when i have bright ceilinglamps in an interior rendering.

i have no idea what causes this! would be vrey thankfull for suggestions.

Edited August 21, 2011 by max.m

[Jon Berntsen]

I suspect wrong dimensions. Is your model in physical accurate measurements? Try turn off the antialiasing and set the sampler to Fixed with subdivs 4 or 5 just for the purpose of testing. Also check that your lightning is not overkill x 10, that could make strange results. What happens if you make the wall gray rather than white? Would the jagged edges be gone? Does it help to tick "clamp output" in the color mapping rollout?

[danb4026]

Try turning on sub pixel mapping in vray color mapping settings. This will usually help with artifacts caused with over bright areas.

[max.m]

thanks for your support and sorry for answering late. i tried your suggestions and saw that the problem is gone with the fixed aa-sampler. so it must be an aa issue. i rose the min subdiv. in the adaptive dmc sampler from 1 to 2 and the max. subdiv. from 4 to 8 and the problem was gone.

i made a lot of render tests also in other scenes and realised that the artefacts only exist in pixels which are between areas of high contrast, especial if one of these areas appears very bright.

now i have to life with higher render times!

 

one more question: i need the better aa-settings only in the described areas. is there another way to handle this, so that i don`t have to rise the the aa settings for the whole image, which was fine?

Edited August 29, 2011 by max.m

[Jon Berntsen]

one more question: i need the better aa-settings only in the described areas. is there another way to handle this, so that i don`t have to rise the the aa settings for the whole image, which was fine?

 

This is a job for the adaptive sampler. It will decide whether a higher sample rate is needed or not. Try setting the max on adaptive to a higher value and I believe it will be better. If not, try to minimize the contrast. Check your 16 bit values of the bright spots. If they are way too high and not in the direct source of the sun, you have a lightning issue that you would be better off with taking care of rather than experiencing higher render times with cranking up the subdiv values of the adaptive dmc.

 

Hope it works out for you.

[max.m]

thanks for the substantive reply jon. i never tried the adaptive sampler as in the documentation is written, that you should not use it when there ist some kind of blurry effect in the scene, which always is in my scenes.

but i will try your suggestions and post my progress.

[Jon Berntsen]

What kind of blurry effects are you talking about? Is it an animation btw? And if it is DOF, you could always try to add that in post with DOF render pass.

[max.m]

i have glossy reflections in the scene, no dof! yes, it is an animation.