I have 3 balls that are travelling down a pipe, I have a background image which I have aligned my pipe to a hole in the image.

In order to make the balls appear as if they came from the hole in the image, I need to mask the balls until they exit the hole.

I have created a piece (selected in the example image) that covers the pipe, but I don't know how to do the masking in the compositor.

Can I use cryptomatte for this or some other way?

See my example image below:


  • $\begingroup$ Yes I believe you're right, I ended up creating a holdout material for the piece that covers the main pipe. $\endgroup$ – Neil Nov 4 '19 at 10:17
  • $\begingroup$ Good, you got it going! I'll delete my comment and link if that's ok $\endgroup$ – Edgel3D Nov 6 '19 at 2:23

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