Transparency not rendering in Surface shader

[hooperized]

I'm trying to get something like a surface shader, a lighting independent material, to render with a supplied alpha matte. I have some textures I want to reflect into an object. I've created an alpha on the texture so that only the parts I want will show up in the render and the dome light with HDR will reflect in the areas that have been alpha'd out. Normally in Maya I would apply a surface shader, plug the beauty (rgb) texture into the "out color" slot and the alpha into the "out transparency" slot. But in vray the whole rgb renders and only the alpha is cut out. I need the RGB to be premultiplied by the alpha like it does in maya software rendering.

any help would be greatly appreciated.

[Zdravko]

I'm not quite sure I understand you correctly. Would it be possible to clarify what exactly you want to achieve?
Some screenshots will be helpful or a simple scene.

[Dariusz Makowski (Dadal)]

I think I know what you want to do... soo is there any reason why you are not using vray light shader and its opacity option? Or does that does not work either?

[hooperized]

That doesn't seem to work either - the opacity doesn't seem to show up in the rgb channel.....I'll start creating a more clear version of my issue, I'll try to post it tomorrow, for now I used a regular vray material and had to change the reflected color in nuke.

[hooperized]

Scene Files and renders for the Issue

Attached are images of the renders using a test scene file.

The compete set up can be downloaded here

http://www.vfxmonster.com/downloads


The problem that I'm having is getting a transparency of the mountians reflecting into the chrome ball without affecting the texture of the mountains. If I use a vray material, the dome light affects the image of the mountains reflecting into it. Where as a surface shader in Mental Ray will leave the texture untouched by lighting.

Thanks again.

[tashko.zashev]

Hi,

The easiest way to achieve this effect is to use the V-Ray Material "Opacity" option, mentioned by DEDAl, but you can get it with Light material or V-ray Material refraction too.
For the file "Vraymtl" where you use refraction parameter to achieve material transparency you can to set IOR value to "1".

In order to get this effect with V-ray light material, you have to prepare correct "Diffuse color" map (the transparent area should be black in order to prevent light emission there).

[hooperized]

Thank you. That works perfectly!! I didn't realize that you needed to black out the Alpha area on the diffuse texture. I figured the opactiy map would have premultiplied that texture before using it to illuminate. Thanks again..