Alpha Transparency Query

[styarc]

Hello,

I have been using V-Ray for rhino to produce an architectural model.

I have created a roof, on top of which I have placed a coloured bitmap on the diffuse layer, and an alpha bitmap (both are .tga) for transparency. The idea is to create a roof with penetrations filled with coloured glass.

When viewed from above, the system works fine. However, when viewed from below, the transparency appears to be boolean rather then greyscale - the penetrations are still there, but they are completely open, where the alpha layer indicates they should be semi-transparent (so that the colour which I have filled in on the diffuse layer can be seen).

I'll note that the roof currently has no depth. This was because the top and underside penetrations would not match up if depth was introduced.

Any ideas why this is happening?

Further, while there are clear openings, the light mapping appears to be reading the roof as a solid entity, and no light is cast through the penetrations. In other tests with say, a checker pattern as the alpha layer, light is cast through the penetrations.

Hope I'm making sense!

I've attached two renders to explain what I mean.

[dalomar_cg]

Re: Alpha Transparency Query

hmm...would you mind posting the maps and your material settings. Off the top of my head I'm not sure exactly what could be causing the issue, all though it appears to be a frontface/backface issue.

The matching of the top and bottom would need to be controlled via mapping. If you simply group them together and map them as one (with planar in this case), then I think that you'd be fine with putting them together.