Facing angle transparency in VRay

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Old 02 February 2014   #1
Facing angle transparency in VRay

Hi, I have a task where I want to show food going through the human digestive system, and want partial transparency on the part of the mesh closest the camera to see inside the organs.

I have successfully gotten maya hardware 2.0 to work in the viewport, hooking up a ramp shader with the color imput set to facing angle into my transparency channel (on a phong), and using a second med with opposite one-sided rendering set.

However, I am rendering with VRay and it tells me it can't render the mesh with the transparency effect, it comes out solid, and I get an error stating that the kRampShader is not supported.

Is anyone here more knowledgeable on how to achieve this effect with VRay?
 
Old 02 February 2014   #2
I just tested it out and it seems to work as expected with both a Phong and a VRayMtl (using a sampler info connected to the vcoord of a black and white ramp which is then connected to the transparency).



Phong on the left and VRayMtl on the right. Hopefully that's actually the effect you are after..

I attached the scene if you want to take a look at the shading network.
Attached Files
File Type: zip vrayFA.zip (25.4 KB, 5 views)
 
Old 02 February 2014   #3
Thanks, looks like what I need...

First, thanks for the response. It certainly looks like you have managed the desired effect, however, the maya file you sent reads as empty (nothing in the outliner or scene), could I trouble you to try again please?

Could you confirm you used a Ramp Shader (not a ramp texture) on the alpha channel?
 
Old 02 February 2014   #4
I don't actually have the scene file anymore, but I downloaded my original attachment and it worked fine for me. I think I might have misunderstood your original post.. specifically this:

and using a second med with opposite one-sided rendering set.


I'm not sure what exactly you mean by this. But in the example I attached I used a sampler info node and connected it's facingRatio output to a ramp texture's vcoord input. If you are using it to drive transparency of another shader (your phong), it should give the same result as you are expecting with the ramp shader/facing angle colour input. I did test it using the ramp shader connected to the transparency of a phong, and while VRay does render it without any errors, it doesn't render as expected (like you see in the viewport or with the ramp texture method). I have attached a new scene maybe this one will work for you..
Attached Files
File Type: zip vray_facingAngleHelp.zip (25.8 KB, 5 views)
 
Old 02 February 2014   #5
Welcome to the forums ultramyth!
 
Old 02 February 2014   #6
I am still unable to see anything in the scene you sent Pollos, maybe a maya ascii would help. In any case, it sounds like I have had a brain fart and written a Swedish word here or there.

It sounds like you duplicated what I was getting. I thought at first it was to do with vray and backface culling, but I don't think so. Your solution may well work, I may try to replicate it myself going off how you said you did it. Thanks.

Thanks for the welcome Rasamaya!
 
Old 02 February 2014   #7
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