Masking

There is a group of "Mask" deformers which allow you to mask the deformers applied to a deformable. Mask deformers will undo the effects of any other Deformers placed above it in the deformer list.

For example, this Box Mask masks the Simplex Noise in this screenshot, removing the noise and revealing the original cube:

The masks work by blending the mesh state towards the last "mask state." The mask state is just a snapshot of the mesh which masks can reference. The default mask state is the original, unmodified mesh, but you can explicitly update the mask state using a Mask State deformer.

To demonstrate this using the previous example, the deformable now has a Sine and Mask State deformer added to the beginning of the deformer list. By adding a Mask State after the Sine deformer, the sine wave is included in the updated mask state and is not affected by the Box Mask.

If the Sine deformer is placed after the Mask State it is then masked by the Box Mask. (And in this case, the Mask State is redundant)

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Note: I am not particularly happy with the current masking implementation and am open to changing how it works.