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Intergrating 3d object into a real scene

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Simon Roughan
Intergrating 3d object into a real scene
on Jul 15, 2011 at 9:31:02 am

Hello again. Still having a bit of a problem with this.
I have footage of a building. I want a 3d element to grow around behind the building and appear again on the other side of it.
I set a still up from the footage as a background, and match the camera to the perspective. I make a simple cube and match it to the position of the building in 3D space. I then grow my element along a spline behind the cube. So heres where I run into a problem. Is there a tag or something that I can attach to the cube, so that in the render its invisible, but still blocks out the element that runs along behind it? Of course, Ive tried the compositing tag with "seen by camera" shut off, but I still see whats behind it.
Any help appreciated
Simon


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randy johnson
Re: Intergrating 3d object into a real scene
on Jul 15, 2011 at 11:10:06 am

In the compositing tag you want to use an object buffer. You also add this object buffer in the render settings (multipass option).

Be sure that it is visible to camera.

The object buffer will be your "mask" or adjustment layer in your compositing program.

/Randy


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Simon Roughan
Re: Intergrating 3d object into a real scene
on Jul 15, 2011 at 11:33:20 am

Thanks for the reply.
I dont quite understand. Should I give the Building or the element behind it an object buffer? Or both?
thanks again
Simon


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randy johnson
Re: Intergrating 3d object into a real scene
on Jul 15, 2011 at 11:40:24 am

The buffer creates a mask for what ever has the buffer... So to remove the building you want it on the building.
Think of it as an alpha channel for what ever has it, your render will still include the building. The multi pass render will only be black and white...so you need to layer it all together in post.

In addition you can place different buffers on different objects and place the same buffer number on different objects to create groups... this is nice for color correction and so on.

/Randy


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Simon Roughan
Re: Intergrating 3d object into a real scene
on Jul 15, 2011 at 11:54:05 am

Now I get it.
thanks for your help.
A Guinness for you, next time your around my way.


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Adam Trachtenberg
Re: Intergrating 3d object into a real scene
on Jul 15, 2011 at 4:12:23 pm

What you want to do is use the compositing tag and check the "compositing background" option. Then create a material with your footage loaded in the color channel (if you haven't already) and place the material on your cube/building. Click on the texture tag and set the projection to "frontal".


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Simon Roughan
Re: Intergrating 3d object into a real scene
on Jul 18, 2011 at 7:49:35 am

So Mr Trachtenberg, and yet again you have saved me a heap of work.
Thank you.


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