Modifiers vs effects
Two stacks, two jobs. Knowing which one you want is most of the battle.
A layer has two stacks, and people put things in the wrong one constantly. The distinction is not arbitrary and it is not about which panel something happens to live in.
- Run before anything is painted.
- Work on geometry — outlines, copies, clipping.
- A Repeater genuinely creates eight things.
- Reorderable: the list runs top to bottom and order changes the result.
- Examples: Repeater, Instancer, Mask, Boolean, Bend, Morph.
- Run after the layer is a finished picture.
- Work on pixels — colour, blur, shadow, grain.
- A Drop Shadow adds no geometry; it darkens pixels.
- Stack in order, each one taking the previous output.
- Examples: Drop Shadow, Bloom, Levels, Bevel & Emboss, every shader.
The test that always works#
Ask: if I turned off every effect, would this thing still be there as a shape? A repeated copy would — eight rectangles exist whether or not anything is coloured. A glow would not — remove the effect and there is nothing left of it.
That is the line. Geometry is a modifier. Appearance is an effect.
The cases that trip people up#
Outlines. Offset Path is a modifier — it moves the actual outline, so a stroke on the shape follows it. Stroke (Outline) is an effect — it draws a border around the rendered pixels. They look similar on a simple shape and behave completely differently on a complex one.
Blur versus roughness. Gaussian Blur is an effect: it softens pixels. Roughen Edges is also an effect, even though it looks like it is chewing the geometry — it is displacing pixels at the edge, not moving vertices. If you need the outline itself to be ragged, that is Wiggle Path, a modifier.
Masks versus Booleans. A mask hides part of the layer; the geometry underneath is untouched and you can slide the layer around inside it. A Boolean actually removes part of the outline, so a stroke follows the new edge. Reveals want masks. Icon construction wants Booleans.
Modifiers always run before effects, and you cannot interleave them. If you need an effect applied per copy rather than to the finished array, put the effect on the source layer and the Repeater on a parent — the parent then repeats an already-glowing layer.
Drivers are a third thing#
Drivers live in the modifier list, which suggests they are modifiers. They are not. A driver does not touch geometry or pixels — it animates a value, the same way a keyframe does. It just does it with a rule instead of a curve.
They sit in that list because that is where you go to add behaviour to a layer, and splitting them into a fourth panel would be worse. But in the pipeline they run at step 3, well before the modifiers proper at step 7.