The [feedback] table

The engine has two accumulation buffers — the trails post stage, which every scene composites through, and the attractor scene’s own internal trail field — and both read their past through the same transform (ADR-0048). The moving parts of that transform are ordinary bindables (fb_zoom, fb_rotate, fb_dx, fb_dy, fb_center_x, fb_center_y, fb_warp, all documented in Parameter roster); the two structural choices are this table:

[feedback]
warp  = "swirl"   # none (default) | swirl | ripple | fisheye
blend = "add"     # max (default)  | add

Key	Values	Notes
warp	none, swirl, ripple, fisheye	Which curated procedural distortion rides on top of the affine. Its strength is the bindable fb_warp. Default none.
blend	max, add	How this frame’s light lands on the faded past. Default max — the engine’s only blend until this table existed.

Both keys are optional and so is the table. An unknown value is a surfaced load error naming what it expected, like every other structural table — a warp kind selects a shader path, and quietly falling back to none would render a look you never asked for with nothing on screen to say so.

Two things about this table surprise people, and both are consequences of there being two buffers rather than one:

• One vocabulary, two sinks. A single fb_rotate on an attractor preset that also binds trails turns both accumulations — the scene’s field and the stage’s — each about its own buffer, neither about the other’s. That is deliberate (one thing to learn, and it transfers), but if you have both live and are attributing the motion to one of them, you are attributing half of it wrong. Turn trails off to see the scene’s own.
• blend reaches the trails stage only. The attractor’s deposit has been additive since the scene was written — its points draw through an additive pipeline over the decayed bed — so there is no max to select there. warp reaches both.

The transform applies to the past, never to the light being deposited this frame: the fresh figure is always where the scene put it, and only the trail behind it travels.