shadow pass accounting for GI?

[jasonhuang1115]

Hi,

How to set up the shadow pass that accounts for GI? (if not using the method mentioned by spot3d tutorial) I bump into this issue yet again and wonder if it is doable at the moment in Vray. Similar questions are posted before but in my test I am still unable to achieve this control in post:

http://www.chaosgroup.com/forums/vbu...dow+pass+%2AGI
http://www.chaosgroup.com/forums/vbu...dow+pass+%2AGI
http://forums.cgsociety.org/showthread.php?t=1090460

In a simple ball on a plane scene (one directional light + one dome light), I separate the scene into three render layers: Ball, Ground, and Shadow. I have tried all matte object settings and visibility settings in the Shadow render layer, I couldn't get a shadow pass that accounts for GI effect, namely the color bleeding observed in the shadow and ground in the Beauty render.

plane shadow ball comp beauty

Thanks!

[vlado]

I don't know of any other way to do it perfectly accurately except as described in the spot3d tutorial.

Best regards,
Vlado

[jasonhuang1115]

Great to get the confirmation you, vlado.
1. Is this a vray-specific limatation (doable in other renderer?)?
2. Why is this not doable in vray?
3. Is this going to be possible in future version of vray?

Thanks.

[vlado]

1. Is this a vray-specific limatation (doable in other renderer?)?

I do not know of any renderer that does this in one pass. On the other hand, the three-pass workflow as outlined in the tutorial works for any renderer.

2. Why is this not doable in vray?

The correct solution is exactly the one described in the tutorial - to render three versions of the scene at the same time with the matte object normal, black, and transparent. I have no idea how a renderer can do this in one pass and still properly account for reflections, refractions, GI and shadows.

3. Is this going to be possible in future version of vray?

We could do it, but we would essentially be doing the same thing - rendering the image three times internally.

Best regards,
Vlado

[Racso]

Hi, sorry for highjacking this thread. I am actually facing the same problem as jasonhuang1115 describes in this thread and wonder if there any solutions for this in VRay 3 for Maya?

That is to have the GI affect the shadow render element.

/Oscar

[vlado]

GI will affect matte objects when they are set to receive shadows; doesn't that work for you? We could probably write that info into the shadow/matte render element too, although, as I pointed out above, it is not entirely correct.

Best regards,
Vlado

[Racso]

Hi Vlado, no I get no GI on my matte object even if I set it to receive shadows. Would it be possible to send the scene for you to have a look at?

/Oscar

[vlado]

Yes, sure. You can send it to vlado@chaosgroup.com

Best regards,
Vlado