After Effects Shape Layer Blending Mode Dissolve Mask Path Glitch / Flicker When Mask Feather 20-150

Question

Two seperate shape layers staked on top of each other. The bottom is white, the stacked on top is black. The black shape layer has an mask set to Subtract ( I have also tested this with Add with invtered checked to the same result ). The Mask Path property is animated to move left to right.

When Mask Feather is set between 20 and 150 pixels you can see a hard line moving along with the mask as it moves. This only happens when the layers blending mode is set to Dissolve. All other blending modes you do not see this glitch / flickering effect.

Please see the three videos attched below. Thank you very much for your insights and help to resolve this issue.

I am using Ae Version 24.02 ( Build 3 ) on an Apple M1 16GB Macbook Pro 13 2020

Rick Gerard · Answer

The Dissolve blend mode creates noise. I am assuming that is what you want. For previews, try setting the Comp panel resolution to Auto. You'll get a better preview than you would with Full and 50% magnification, and the comp will take less time to preview. You might also want to set the Project color depth to 16-bit. It doesn't show, but 8-bit comps with gradients are subject to banding.

When you feather a mask and animate the feathering, subtle changes in the opacity of the layer create the noise. Animating the mask only makes things worse. If you were to animate a Gradient Filled layer's gradient shape and slightly reduce the opacity layer to bring up the grain structure from the Dissolve blend mode, you would eliminate the changing noise patterns.

I'm not sure why the noise behaves as it does in your example, but I get the same kind of rectangular noise block when I do, Changing the shape of the mask to more of an oval changes the size and position of the dancing noise block.

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