I am using Blender 2.76.

I want to layer this movie clip: enter image description here

over this one: enter image description here

So far this is what I have: enter image description here

using this set of nodes: enter image description here

I set "Dilate/Erode" to -100 to achieve this effect. The compositor takes about two minutes to create the image. I would prefer the top image be completely opaque rather than slightly translucent.

I am wondering, is there a better way to achieve the effect I am looking for? Is there a method that will not require two minutes to composite one frame?

Thank you!


This set of nodes solved the problem, thanks to Troy_S: enter image description here

Edit #2:

I tried the "Math" version but it did not work properly. I am hoping Troy_S will let me know how to correct my error: enter image description here


Two ways spring immediately to mind, assuming zero emission backgrounds:

  1. Take the output of the image and roll it through a node to get the maximum value.
  2. Set Alpha on the image from the result from 1.1.
  3. Use a generic alpha over and done.

For a more abstract glowy vibe:

  1. Take the output of the image and roll it through a colour to BW node.
  2. Set Alpha on the image from result from 1.1
  3. Use a generic alpha over and done.

The former is a generic alpha over on imagery with zero emission background. The latter is a generic alpha over, but will result in some values being semi-additive akin to fire / candle flames.

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  • $\begingroup$ Could you please show me your procedure? I am new to this and am not clear on what you mean. Thank you! $\endgroup$ – Kermit Sep 3 '19 at 3:34
  • $\begingroup$ Try the second one first. Add the image. Route to a RGB to BW node. Use the input from the image on a Set Alpha node, and use the output from the RGB to BW as the alpha. Repeat for all images you have, and simply alpha over. For the Math node Maximum approach, you will need a Separate RGB, then two Math Maximums to derive the maximum value from the three RGB channels. Same as above for Set Alpha. $\endgroup$ – troy_s Sep 3 '19 at 17:06
  • $\begingroup$ Thanks! I am editing my question to include the solution nodes. $\endgroup$ – Kermit Sep 4 '19 at 1:16
  • $\begingroup$ I tried the Math version but it did not work, probably because I did something incorrectly. I am going to post an image of the nodes to the question, and could you please tell me where I went wrong? $\endgroup$ – Kermit Sep 4 '19 at 2:23
  • $\begingroup$ The maximum is the problem. You want the maximum of the three RGB emissions, then use that. So the R and G go to Maximum, then the out goes to a Maximum with B. The out of that routes directly to alpha of Set Alpha, with the RGB input being the original image. $\endgroup$ – troy_s Sep 4 '19 at 5:05

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