Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: andych82 on 2016-05-20, 00:17:24

Title: Glass Refraction
Post by: andych82 on 2016-05-20, 00:17:24

Hey all,

I had a question about glass materials. So I'm working on a lens of sorts, I can't share the scene because its under NDA, but basically its like a camera where there are many cone shaped glass pieces in a row. When I made a corona material with a diffuse of black, full reflection/refraction + gloss of 1, it seems the more glass lens geometry I place in a row, the darker the reflections/refractions get. Does this sound accurate?

I was hoping I was just keep placing glass in front of each other and it would just refract geometry without losing light, but the refractions seem to be getting darker with each glass piece. Is there a way to maintain brightness with multiple pieces of glass in a row?

Not sure if this makes any sense, but figured I'd ask because there are a lot of smart people here.

Thanks.

Title: Re: Glass Refraction
Post by: Juraj on 2016-05-20, 01:17:41

Can you try setting MSI to 0 and see if that changes ?

Title: Re: Glass Refraction
Post by: andych82 on 2016-05-20, 01:35:29

That seemed to help a bit. Thanks for the suggestion. I also just tried lighting the lens more from the back and I disabled GI for the glass with the rayswitcher mat. Still seems too dark but I think its my user-error with the way I've setup the scene.

Thanks.

Title: Re: Glass Refraction
Post by: andych82 on 2016-05-20, 01:43:20

So you were right, the MSI set to 0 helps the brightness a lot, but it's also taking forever to render the glass now haha

Title: Re: Glass Refraction
Post by: FrostKiwi on 2016-05-20, 10:21:07

Quote from: andych82 on 2016-05-20, 00:17:24

but basically its like a camera where there are many cone shaped glass pieces in a row.

If you have many refractive volumes in a row, you might brake the 25 max ray depth limit, after which a ray dies and no more light is being transfered.
This article for detail.
https://coronarenderer.freshdesk.com/support/solutions/articles/5000547502-what-is-max-ray-depth-

Title: Re: Glass Refraction
Post by: romullus on 2016-05-20, 11:00:09

The easiest way to check if that's the case, is to enable devel/debug rollout in render setup>performance tab and to change exit colour to some bright saturated colour.

Title: Re: Glass Refraction
Post by: Juraj on 2016-05-20, 11:01:10

Quote from: SairesArt on 2016-05-20, 10:21:07

Quote from: andych82 on 2016-05-20, 00:17:24

but basically its like a camera where there are many cone shaped glass pieces in a row.

If you have many refractive volumes in a row, you might brake the 25 max ray depth limit, after which a ray dies and no more light is being transfered.
This article for detail.
https://coronarenderer.freshdesk.com/support/solutions/articles/5000547502-what-is-max-ray-depth-

But would this also cause progressively darker refraction ? I thought it would simply be a cut-off after threshold has been reached.

Title: Re: Glass Refraction
Post by: Ocularcentric on 2016-05-20, 15:36:49

Could it be possible that each "lens" is allowing some rays to refract out of the chain into the scene and therefore with each lens a percentage of the input light is lost.....resulting in dimming effect? Agree with Juraj that you would get a sudden change to black (no light) once you reached the bounce threshold. This was a common problem back in the day