weird alpha channel issue

[sublevel4]

Ok here is what i have.
I have a car with a composite material. In the composite material there is a base paint, layer then a light decal layer which is a standard max matherial with a defuse map and an opacity map, then a decal layer that is a vray material with a defuse map and an opacity map. My problem is this. When i render the rendered image come out fine. you can see the base paint under the other two layers. However when i look at the alpha channel the paint layer is gone. It looks as though the decal mask is masking everything in the lower two layers. This setup worked fine the 1.46 vray but now that i have 1.5 it isn't working. I am at a loss as to what the problem is. The attached images show a crop from the render and the same crop from the alpha channel.

Anyone have any ideas why this happens and what the fix is?

[vlado]

I suppose the fix would be to use a VRayBlendMtl material instead.

Still, if you can email me your material applied to a simple sphere, I will be able to tell you more about the issue.

Best regards,
Vlado

[Inhance Digital]

Alpha issue...

This is actually a really big issue.

To show the effect its as simple as creating a sphere with a composite material type on it (2 vrayMtls). On the fist material for slot 1 change the diffuse color and put a map in the opacity (that defines what is shown thru onto the base mat). That opacity map on the overlay material holds out the alpha.

This is quite a headache after converting to vray mats and having to go back through composite materials and turning them to vray blends.. which is handled really differently it seems.

Am I missing something??
-will

[vlado]

The original bug was fixed in SP1 and renders fine there. However, there are still some alpha oddities when mixing V-Ray and standard 3ds Max materials; I will try to resolve these eventually somehow, but for now you are only guaranteed a correct result when using only 3ds Max or only V-Ray materials. V-Ray materials are a lot faster to calculate too, especially when you add several layers.

Best regards,
Vlado