vraymtl (Glass) with vray matte

[dgsantana]

Hi, i found a "bug" that seems to happen when there is glass (vraymtl) and behind it there a vraymtlwrapper (with alpha -1) to serve has a matte. When i see the alpha channel, the parts that are have the glass in front the matte loss the alpha and this doesn't happen with a standart material. (still we can't use a standart material with refraction has the render gets full of splotches).

[jacksc02]

can you show somw images of the problem?

[dgsantana]

Here it is:



is has low quality because i have little time to render. The deadline is tomorrow.

[jacksc02]

does the glass have affect alpha checked?

[dgsantana]

yes, and affect shadow also. (tried a fiew combinations)
I believed that has something to do with the reflections. I have ETFE for the ceiling and had to disable the trace reflections so it render ok.

[jacksc02]

whats the alpha contribution of the glass set to in the vray properties?

[dgsantana]

-1. That was one of or problem in the past but since vlado told to use -1 (in some post) it works like a charm. Also we have some outdoors that we use alot this settings for post processing.

[jacksc02]

you could always turn off the glass and render a seperate alpha pass

[dgsantana]

that would be an option if it wasn't so complex in some of the images. in are taking the aproach of not having refractions and using a standart material. but still this some to me like a bug. could be wrong.

thanks anyway jacksc02.

[jacksc02]

do you have an hdri in the reflection/refraction slot?

[dgsantana]

yes. do you think this is the problem? it was the only thing i havent' change.

[jacksc02]

it can be problematic.
Take out the hdri and see if it helps

[dgsantana]

Well i just check and after all i'm already disabled it. i tested some many combinations that i can't remember all. i would setup a small scene but just this scene is 1.7gb opened in max and can't tested right now. but a simple setup would be put a vraymtlwrapper with a standard or vraymtl in it and put a vraymtl glass and set the alpha to -1 in wrapper. also i tested with irrandance/lightcache, irrandance/qmc, lightcache/lightcache.

[dgsantana]

now that i had the time here it is an example of the problem, and a test scene. hope someone can shed some light into to this.



scene
http://www.4arq.net/stuff/refraction_test.max

[vlado]

This is not a bug - matte materials/objects act as "mattes" only when seen directly by the camera. In all other cases (e.g. in reflections, refractions etc) they will appear normal. It may help if you make your glass transparent, rather than refractive.

Best regards,
Vlado