View Full Version : DOF footage + 3d elements ?

12 December 2008, 03:12 PM
How can I add a 3d geometry to a street full of people,
close ones are blurred, far ones are sharp.

I want to add the geometry to the middle, and its action footage,

I can do the camera matching and everything, but how can this "dof" problem be solved ? The geometry is behind the people, and they can not be keyed because its a random street on a ramdom day..

Well, waiting for some replies. I'm new to compositing footage with 3d elements.

Thank you.

12 December 2008, 11:38 PM
The best way is to rotoscope the FG people, and use that matte with some blur that matches the dof to hold out your CG element.
You might have to use a few rotoshapes with different blur levels to get a good result

12 December 2008, 03:33 PM
Hmm, but people are moving, so how will I apply the "more" or "less" blurring ?
I could solve it if it was a single frame, but, when they come closerthey have to blur more etc.

keyframing seems......... like a hard way. ?

12 December 2008, 08:20 PM
welcome to visual FX.
yes, you will need to rotoscope the FG people across the length of your shot,
and you will probably need to keyframe the blurriness.

12 December 2008, 05:54 PM
What software are you using?
Are you planning on adding DOF to both the 3d geometry as well as the people moving?

You can get a Z-depth pass from the geometry in Maya for example. and use that to drive the DOF in the compositing program.

If you're using shake, do not use blur, use defocus (they work very different, and blur wont look right to simulate DOF).

And yes, you will most likely need to roto the people (unless they have a really strong contrast from the background (try all the channels, RGB if that might be the case), then you can use a lumakey.

If anything is confusing, let me know and I can try to go into more detail.

12 December 2008, 04:52 AM
Like the others have mentioned...Roto the FG people for the length of the shot. Render out your 3d element and just keyframe some defocus. Break up the 3d object with some masks, or you can render it out with a Z-depth pass. Pretty basic fx work.

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12 December 2008, 04:52 AM
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