Page 1 of 1

stains on transparent glass

Posted: Mon Apr 08, 2019 11:32 pm
by Kroustinio
hello,
can you tel me how to fix the problem of stains that appear on windows in my render ?
It's seems to happen in the dark parts of the scene, where are shadows...

this image was rendered with 20 000 samples per pixels. I think more samples would be better, but I'm not sure.
Thanks for your suggestions and forgive my approximative english.

Image

Re: stains on transparent glass

Posted: Mon Apr 08, 2019 11:37 pm
by Zom-B
You took some glass from the Material Database?!
Use architectural glass for such windows!

It also seems you rendered with MLT, right? Use it only in special cases where you know what you are doing, stick to BiDir on CPU or PT if you have a beefy GPU :)

Re: stains on transparent glass

Posted: Mon Apr 08, 2019 11:40 pm
by Kroustinio
it is quite strange : I show you this previously rendered image with a limit of only 15 000 sample per pixels, wich was perfect.
On the other hand the HDRI image is not the same.

Image

Re: stains on transparent glass

Posted: Mon Apr 08, 2019 11:45 pm
by Kroustinio
thanks for your answer : yes I used indigo MDB glass material.

What do you mean by architectural glass ?
What is MLT ?

the images where rendered with Ranch Computing render farm

Re: stains on transparent glass

Posted: Mon Apr 08, 2019 11:46 pm
by Kroustinio
both glass canopy material are the same in this renders

Re: stains on transparent glass

Posted: Tue Apr 09, 2019 12:01 am
by Zom-B
MLT = Metropolis Light Transport, a render mode that Indigo supports.
It superior in certain fields but usually not for interior rendering.
Be sure to use PathTracing with BiDir

Arch Glass is Glass that lacks refraction. Its used for plane windows to have faster rendering.
It should be a checkbox for a specular material, depending on your 3D program...
Don't use it for Glass objects like the drinking glass on the table

The material you use from the MatDB has either some SSS enabled or cauchy_b value above 0.

Re: stains on transparent glass

Posted: Tue Apr 09, 2019 12:15 am
by Kroustinio
Just checked : I used th Bidirectionnal Path thracing in Indigo. No Mlt

I think I will try to improve the level of SPP in the rendering farm, just to be sure.
But it's expensive !

Re: stains on transparent glass

Posted: Tue Apr 09, 2019 12:21 am
by Zom-B
Try the attached Material for your Windows and the shelf, it should fix the stains.
ArchGlass.zip
(464 Bytes) Downloaded 17 times

Re: stains on transparent glass

Posted: Tue Apr 09, 2019 12:26 am
by Kroustinio
thanks, but if no reflections : no realism ?

Re: stains on transparent glass

Posted: Tue Apr 09, 2019 12:38 am
by Zom-B
it misses refraction.... not reflections. Test it!

Re: stains on transparent glass

Posted: Tue Apr 09, 2019 12:43 am
by Kroustinio
Ok, thanks, Zom-B