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I have two clips:

  • One is background footage (shaky cam) that I have tracked and solved, set up scene in Blender, etc.
  • The other is a .exr effect sequence rendered from Houdini

I would like to layer these on top of each other, but I want to use the camera track on the EXR sequence, so the Houdini effect follows the scene. I tried adding the sequence as a plane, but Blender rendered the EXR files with a black background, even though they showed up with alpha in the image viewer.

Any way to layer these two clips so that the effect follows the main shot using the camera track data?

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  • $\begingroup$ Use the stabilize node on the EXR sequence with the information from the tracked footage. $\endgroup$ – user1853 Dec 24 '19 at 23:59
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If you simply want it to follow one of the tracks, what you're looking for is the 'Track Position' node (in the Input section of the compositor node list). Just give it the video clip and a track that's the same depth as the effect you're adding. Excuse the lack of actual files in this example, but in the compositor, create the following (vector blur is optional):

Track position and CG sequence fed into transform node, fed into an alpha over with the background clip

You may need to add another transform node to just the EXR sequence so it lines up correctly.

Just to cover my bases, if you need a more 3D layering, you'll add the sequence to the Blender scene projected onto a mesh, plane or otherwise. To include alpha as part of the plane, you just need to use the alpha as a factor of a mix shader:

enter image description here

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