Use Background Shader Rendering

[achoury]

Gday, I'm trying to render out some road cracks (texture) layered over a Use Background Shader so I just get the cracks over an alpha channel. Rendered as a file with no alpha it comes up just fine but the cracks texture doesnt seem to generate an alpha channel so any file type like .iff it will come up blank. Any ideas or a different way to do it would be appreciated.

Try using mip_matteshadow ( production shader) rather than Use background shader.
here is a video-tutorial (http://www.mymentalray.com/index.php?option=com_shaders&Itemid=127&Action=DisplayDetail&ObjectId=130) showing how to generate shadow with mip_matteshadow

/rachid

[cheebamonkey]

you mess with the matte opacity in the useBackground? Is you layered texture set up correctly?

[krumme]

I havent messed around with the matte opacity, I tried layering the texture over the the useBGS with multiply, add, etc, then i mapped it to a blinn with transparency and layered that over the useBGS , still not generating an alpha channel, I'm sure theres a way to do it I,m just not seeing it.

[MasterZap]

I have to re-iterate what previous poster said; don't even try Use Background in a serious mental ray rendering, use mip_matteshadow instead from the production library.

Read me' blog for more details (http://mentalraytips.blogspot.com/search/label/production%20library).

/Z

[krumme]

cheers i'll give it a read

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