Shape Alpha (Mask) This filter makes a snapshot of the frame before an alpha channel (transparency) is created based on another resource. Use it together with the mask_apply effect, that uses a transition to composite the current frame's image over the snapshot. The typical use case is to add effects in the following sequence: this effect, zero or more effects, mask_apply. Charles Yates, Dan Dennedy Filter Image or video resource Threshold Convert alpha or luma values below this level as opaque and above this level as transparent. This is mostly useful for luma wipe images. Softness When using mix (threshold) how soft to make the edge around the threshold. 0.0 = no softness, 1.0 = too soft. Invert Use the inverse of the alpha channel. Use Luma Use the image luma instead of the alpha channel. Use Threshold Whether to apply a threshold filter to the luma or alpha or not. If not, luma or alpha value of the resource (File) is copied to the alpha channel. Offset Start position for the mask file. Out End position for the mask file.