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Adding a CGI model to a live backplate??

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varga edmond
Adding a CGI model to a live backplate??
on Mar 14, 2010 at 10:18:11 am

Hi,

I was searching for hours, but I could not find some reasonable documentation on integrating my model into a 2d photograph. I get the idea of aligning the image plane with the photograph's plane (projected by a separate camera), but I am stuck when it comes to reflections and shadows.

Could someone point me to any source of information on this topic?

Regards! :)




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Stuart Christensen
Re: Adding a CGI model to a live backplate??
on Mar 14, 2010 at 5:24:17 pm

Hello, I'm not that familiar with the process but from what I've read it seems that you can achieve this with the "use background material" option..

essentially you choose View > Image Plane > Import Image from the cameras workspace view menu. Then align a Nurbs plane to the perspective of the photo. The nurbs plane is then assigned to a "use background material". This plane will essentially pick up the shadows and reflections from the attached image and impart these values to your model.

Hope that helps. STU

I know alot....but not as much as the other guy.


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varga edmond
Re: Adding a CGI model to a live backplate??
on Mar 14, 2010 at 5:38:56 pm

Thanks for replying to my message.

So I was doing some more research on this. Indeed, the "use background" shader works!! But I have noticed that final gather has no effect on it. So if I try to light my scene using indirect lighting the plane to which I assigned the use background shader becomes pitch black. Why?? :)


Regards!!


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Stuart Christensen
Re: Adding a CGI model to a live backplate??
on Mar 15, 2010 at 2:33:03 am

I believe this is because the "use background material" also serves as an "alpha punch" that will cut holes through other objects and needs to be rendered out in it's own pass.

You may notice that the shadow cast by the model is on top of the image plane. If the image plane is removed from the camera and the model is assigned to a 100 percent transparent lambert material, the shadow is rendered by itself and appears in the alpha channel. This makes it possible to render shadows out on their own pass. If the shadows are rendered separately, you can composite them back onto a static background.

For this to be effective, the cameras background color attribute (environment camera attribute) should be set to black. Basically it all has to do with alpha channels and perhaps the actual Maya program documentation will provide further illumination. Good Luck. STU

I know alot....but not as much as the other guy.


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