Question about vector blur

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  08 August 2012
Question about vector blur

Is there a way to get a decent motion blur using vector blur if the character is not separated from the background?

I rendered out this image with velocity pass. When I apply vector blur using velocity as uv channels, they always look incorrect with weird hard edges. In this case, on the left side of the head.

Now if I use the character's matte as alpha, the motion blur turns out better and closer to what I expect. But overlaying it on top of the original non-blur image produce some very weird results.

Does this mean I should always render out the characters as separate pass from the background plate? Is there anyway I could make this work without separating them?
Attached Images
File Type: jpg vector-blur.jpg (20.9 KB, 39 views)
File Type: jpg vector-blur2.jpg (9.6 KB, 38 views)
  08 August 2012
Try rendering out a single frame of rendered motion blur to compare it to. You might need to adjust the offset, scaling or direction of the vector blur and having a reference frame to compare it to might help get you closer to a higher-quality result.

Personally I'd forget about post motion blur and render the motion blur. Especially if your using a renderer like V-Ray to get physically-plausible lighting and shading it doesn't make sense to skimp on the quality by using physically-inaccurate motion blur. For the hit in render time you'll probably save yourself and your compositors a load of effort.
  08 August 2012
Thanks Will! I haven't played with Vray motion blur yet, I should get to it!
  08 August 2012
you really should render the fg and bg separate if you want to motion blur the fg.
  08 August 2012
you can add some blur to your vector pass in will work for some case...
  08 August 2012
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