Rotopaint equivalent in Blender? ***how to paint masks in compositor***

Hi all,
I was wondering whether there was a way to paint masks in the compositor. Basically a Natron/Nuke rotopaint equivalent mode, where the mask can be painted live, with a brush.
This would be immensively helpful for integrating CGI into photos/movies but I couldn’t find a way to paint a mask.
I was only able to use the vector mask, which is good for some areas and larger details, but being able to paint in the details (such as a leaves on a tree) is impossible with a vector mask.

Many thanks

You could just add another image as a mask and paint it in the image editor

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I was thinking something along the same lines.

Is there a way to paint an animated mask?

Animating image masks is tricky. It is much easier animating vector masks. You can even camera track the points on to objects you wanna mask.

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btw, cant you mask the leaves by sampling their color?

Thanks Xeofrios, I tried that way, created a new BW image in Blender and used it as a mask.

The problem is that if I paint on that I can’t see the composite result because I am seeing the BW mask. I can put the composite result in a separate window but that’s “painting in the dark”.

In Natron/Nuke/Fusion one can paint on the composite image directly and see the result instantly. In Blender there is no way to paint a mask on the composite output in the Image Editor. At least I can’t find it…

I can key the leaves but it is a much more universal problem, there are multiple element to be masked out, and I was wondering whether there was a simple solution I wasn’t aware of.

Yes, very much right. That’s a shortcoming of Blender I do not know a solution to, if any.

I wonder if they could convert a grease pencil animation into a mask of sorts, it renders quickly and can be keyframed/sculpted, etc.

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I thought of a way you could do it. But it is probably not worth it.

  1. Decrease the brightness of the image you wanna mask and save the image as 1
  2. Open 1 in the image editor
  3. Paint the areas you want to mask with white
  4. Save the image as 2
  5. In the compositing workspace, subract 1 from 2
  6. Adjust the levels
  7. Use the result as the mask

Haha, that’s certainly an interesting idea but probably too complicated and slow.
But thanks anyway!