frosted/milk glass tip please

wojtek-w · Post by **wojtek-w** » Thu Dec 20, 2012 9:55 am

hi,
i need some help with semi-transparent panels in my render.
Below is about 1k spp sample.
As You can see, the render is still loooong way to be clear.
Material is "frosted glass" from material database, panels are 6 mm thick. I did some test with glossy-transparent and specular materials too.
Architectural glass acceleration is on. Indigo is 2.6.1 version.
Is there any way to speed things up?
In this case render performance is much more important to me than physical accuracy so some cheating tricks are also welcome.
thanks.

Post by **OnoSendai** » Thu Dec 20, 2012 10:00 am

Do you have bidirectional on?

wojtek-w · Post by **wojtek-w** » Thu Dec 20, 2012 8:00 pm

yes.
skp exporter reminds it when glass acceleration is on...

Pibuz · Post by **Pibuz** » Fri Dec 21, 2012 4:41 am

...whites checked? 208 208 208 max, remember!

Also, check if your model is clean (purge all to clean all duplicate geometry, unused mats, components, groups..), and also make sure that your metallic geometries, if groups, are detached from the other surfaces in an amount of 0.5mm: it gives more correct results and speeds up the calculation.

William · Post by **William** » Thu Dec 27, 2012 9:22 pm

Glass accel doesn't work well at all for frosted glass. Maybe it should be "ignored" if possible for glossy glass materials.

accell on (10min 40s 1000spp):

accell off (10min 0s 1000spp):

zeitmeister · Post by **zeitmeister** » Thu Dec 27, 2012 11:32 pm

Getting fireflies after a long render time here too...
Even blending a simple glass material with phong results in fireflies.

tremo · Post by **tremo** » Fri Dec 28, 2012 9:37 am

Try it this way. Behind the glass plate at a distance of 0.1 mm a surface texture with a transparent PNG. Texture size 0.1 mm so that the pattern is not visible. Cheap frosted glass panels are manufactured so similar.

CTZn · Post by **CTZn** » Fri Dec 28, 2012 1:04 pm

I see two options though there may be more.

First off I would use MLT and augment the supersampling. The impact on fireflies may show the original recipe worth it.

Or, because I don't see a good way to fake glossy glass, I would render a material ID pass and use it to create a selection to be blurred in a 2d application. Assign all objects one material and keep the glossy where it is, the mask should pop out.

Also if you use the genuine method try to have clear glass on the panel's edges (ie all 4 faces) instead of the glossy material, that will cause less complex paths to happen I would assume. The trick here is to have both materials, the glossy and the clear glass, to share the same medium.

Post by **OnoSendai** » Sat Dec 29, 2012 2:56 am

btw, I am doing some work on the glossy transparent model currently which should improve it a bit.

tremo · Post by **tremo** » Sat Dec 29, 2012 6:55 am

Good method, which I had forgotten this one is.

CTZn · Post by **CTZn** » Sat Dec 29, 2012 9:16 am

tremo wrote:Good method, which I had forgotten this one is.

Agreed. Reportedly this method is slower than using the Glossy Transparent material but it's a good option if it prevents fireflies to happen this much.

wojtek-w · Post by **wojtek-w** » Sun Dec 30, 2012 12:51 am

Hi,
thanks for all ideas.
I did some test with phong material with clip mask value set to 0.5. In my case it should work but i'll check Yours solution too.

CTZn wrote:I would render a material ID pass and use it to create a selection to be blurred in a 2d application.

How can i do that with skindigo?

cotty · Post by **cotty** » Sun Dec 30, 2012 1:49 am

wojtek-w wrote:
CTZn wrote:I would render a material ID pass and use it to create a selection to be blurred in a 2d application.
How can i do that with skindigo?

wojtek-w · Post by **wojtek-w** » Sun Dec 30, 2012 2:12 am

hi cotty,
I'm using skindigo 2.6.1 and I don't see this option
I belive "ID pass" it's a feature I can't use without 3.x version

thanks anyway