AP Live Filter Layer: Mask Layer vs. Clipped Child

[Haffinity]

I have a question about the difference between using a Live Filter layer as a clipped mask layer and a clipped child layer. When I add a Live Filter to an active Pixel Layer, it is created as a Mask Layer. But I can also create it as a clipped child layer with the mouse. The difference in the result surprises me. Can anyone explain the difference?

I have built an example with Box Blur to show the different results.

 

Live Filter.afphoto

[lepr]

You see that the result of a blur extends outside of the border of the source object.

Clipping restricts the visibility of the child to the interior of the parent, therefore the result of the blur (the child) is rendered only inside the border of the clipping parent.

[Haffinity]

Thank you, @lepr

I see. Now I also think, I understand better the difference between a Live Filter Layer and an Adjustment Layer, something that always puzzled me. A filter usually needs to inspect the neigborhood (more or less wider) of each pixel whereas an adjustment layer adjusts the pixels independently of their neigbors. Therefore it makes sense to apply Live Filter Layers as Mask Layer or as released standalone layer.  Clipping hinders the filter algorithm, one could even assume that in this case its result is undefined, maybe you are lucky and the effect is usable.

 

[lepr]

36 minutes ago, Haffinity said:

Clipping hinders the filter algorithm, one could even assume that in this case its result is undefined, maybe you are lucky and the effect is usable.

No, clipping doesn't hinder the filter algorithm. As I said before, clipping restricts the visibility of the filter's result.

[NotMyFault]

The child layer position (masking/clipping) influences how colors and alpha values of the child layer get used.

• in masking position:
  • alpha values will impact the full canvas, unrestricted
  • color values (e.g. RGB channels) are simply ignored. Only color values from lower layers incl. parent will be blended, but the alpha value impacts the blend results.
• in clipping position
  • alpha values are clipped to the parent layer (where parent alpha is above 0)
  • color values are used (blended regularly), but again clipped to the parent layer nonzero alpha pixels.

this applies to all layer types (pixel, mask, adjustment, filter).

there are some exotic edge cases (stack use alpha as binary values), and groups (including Layer layers, symbols, compounds) are beasts on their own.