VrayLightMtl doesnt cast any Alphashadows on Mattes

[Flame@chaos]

Hi,

i have a scene with 4 cylinders with the vraylightmtl applied.
The problem is, that the shadows casted by those cylinders do not appear in the alpha channel of matte objects.

Can anybody give me an explanation ?

Flame

[Flame@chaos]

Anybody any idea ? Or is this question too easy ? Haven t found anything about this anywhere.

[Gijs]

GI shadows don't work on mattes in general, because it is in fact no shadow that is being casted. It's the same as store lights with irradiance map. you won't see the shadows on mattes either in that case.

[Gijs]

BTW: why do you have that name? Doesn't sound friendly...

[Flame@chaos]

I wanted to choose Flame. But it was allready taken as usual. So i named me Flame@whatever (in this case chaosgroup.com) to have a rule for my name, so i don t forget my logins for all the pages or forums i participate.
if this where love.com ... i would be called Flame@love

[Flame@chaos]

But normal GI Shadows casted by the environment f.e. show up in the alpha of any matte. Whats the different between Vraylightmtl or selfilluminated objects and the Environment GI ?

[Morbid Angel]

the difference is that environment emitted rays can be assumed the same way as vrayDomeLight rays and can be traced for first hit, but object to object emitted gi is different. So to be able to catch the object emitted gi you need to make all your objects black and gi emitter invisible to camera. Then in post use screen or add to apply the emitted gi pass. Or, infact you can use vray raw gi pass from gbuffer. Its similar idea.

[Flame@chaos]

Ok, i ll give that a try.

thx