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I'm trying to circularly fade an image into transparency in the blender compositor.

My approach was to use an Ellipse Mask in combination with the Set Alpha node, so that the picture becomes more and more transparent towards the edges.

Node Setup i've used.

Output of the Set Alpha Node:
The render result of the 'Set Alpha' Node.

Unfortunately, this doesn't work as the center turns black where it should be transparent. (The original image has a transparent background.)

What am I doing wrong?

This behavior occured in Blender 2.91.2 and 2.83.5 (on Linux).


In the example used, I try to get rid of the shadow that protrudes over the edge.

The effect I like to achieve would look something like this:

Expectation of render result.


EDIT:

Unfortunately, if the Ellipse Mask is inverted the outer area turns black (should be transparent).

Node Setup of the suggestion.

Output of the Set Alpha Node:
The render result of the 'Set Alpha' Node.

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  • $\begingroup$ Sorry if I'm misunderstanding, but couldn't you just put an Invert node between the glare and the Set Alpha? $\endgroup$ – Christopher Bennett Feb 21 at 1:59
  • $\begingroup$ @ChristopherBennett Thanks for your suggestion. I've reworked the question to address it. $\endgroup$ – AFoeee Feb 21 at 13:07
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The problem is that your node setup is ignoring the existing Alpha channel. Instead of overwriting it, you need to multiply it with your mask.

I used the Separate RGBA node to extract the current Alpha value, and a Math node to multiply the two values:

Node setup

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