EyeonTips:Manual/Fusion 6/Paint
From VFXPedia
To create a mask of the area that was affected by the paint tool, instead of using a Difference Key or duplicating the whole paint node, insert a Channel Boolean before the paint tool that sets the alpha channel to black. Now all your paint strokes will be "recorded" to the alpha channel. For this trick to work with the clone brush, the clone source has to be set to a node that has a solid alpha channel, for example the node preceding the Channel Boolean if you want to clone from the current image itself.
Explanation of the Overlay, Still Source and Snap Offset options when using the clone brush:
- Overlay will display your source (from which you clone) transparent over your image, so you can see what you will be cloning.
- Still source will let you select a frame from your source to use as a still for cloning. Your Time Offset slider will change into a Source Time one when selected.
- Snap Offset refers to the brush itself. When clone painting, press Alt and drag to set the Offset from which to paint. Snap Offset will make sure the Offset is always full pixel values away, so you won't have sub pixel sampling issues with your painted areas. Good for clone-painting noisy footage for example.
(source: this pigsfly post by SecondMan)
