matte material in vray?

[shaggray]

i tried max matte material in vray: i renders correctly, but alpha is always
opaque and shadows don`t affect alpha. what can i do?
thanks
shaggray

[egz]

Use the matte support in VRay instead, either through VRay properties in the quad menu, or with a VRayMtlWrapper.

[shaggray]

hi egz,

i tried what you told me but i dont`get the result i want.
the attached picture shows max`s lighttracer (top)
and vray (bottom) plus both alpha channels.....


please, can you tell me what i am doing wrong?
thanks,
shaggray

http://www.mvd.org/beton/hdri_teapot_rgba.jpg

[egz]

Set the matte objects alpha contribution to -1 and turn on shadows and affect alpha

Like this:



Same settings would apply to the VRayMtlWrapper as well.

[shaggray]

aaaahhh!
the "alpha contribution" setting was my stumbling block!

[flipside]

Why -1 for alpha contribution? I noticed that changing this between -1 and 0 has no effect.

[egz]

put something behind the matte object and you will see.

1 gives you a solid alpha
0 gives you a transparent alpha, showing the solid alpha of objects that might be behind it
-1 will mask out objects behind the matte object as well