Help! Using VRay RT GPU to create shadow matte by mtlWrapper

Hi:
My first thread:) Thanks for your attention and help!
Vray 2.3, 3Ds Max 2013, Quadro 2000 graphic card.
Recently I found a problem with Vray RT using GPU. I did searched everywhere but no luck at all.
selecting renders:


The scene is a teapot on ground, and I want the ground only receive shadow from teapot(affect alpha)

I use mtlWrapper and apply it to ground as shown in pic, then in obj properties check See through.


As you can see, if I use CPU, the ground is not there, everything is perfect.

but in GPU mode, the gray ground appears. I changed nothing else except engine type.



I think the warning regarding GI is not relevant to this problem, since I did tried to open it but no luck.
It confused me for a couple of days, and I tried hundreds of combinations, if anyone can help, please...... I don't want to give up GPU rendering, you can see on the right up corner, GPU rendering it way faster than CPU, I'd rather solve this problem and make our job faster.
This is the scene file if anyone want to test it.
https://dl.dropbox.com/u/12835684/CGtalk/testScene.max

In your matte material, uncheck "receive GI" and "generate GI".

I tried to uncheck receive GI and Generate GI, it don't work either.
any thought?
Do you think this may caused by some function that GPU render doesn't support?
Thanks.

That's wired...I think I replied you yesterday but nothing shows up here, do they need to double check my post?
I tried your suggestion but it won't work either.
Do you think this might be one of functions that GPU render doesn't support?
Also I realized that GPU can not render vray car paint material and glass material very well(picture will upload soon), I feel like this problem might relate with ray tracing or so, any idea?

Still no one? hmmm, alright, I will keep posted.

The mtlwrapper is not supported by the RT using GPU, you can find the list of supported features in the help:
http://www.spot3d.com/vray/help/rt100/render_gpu.htm

Its also a good idea to post questions about vray in chaos group foruns.

Yeah you are right, that's just because an unsupported feature.
Looks like GPU rendering has a long way to go.

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