Parametric Peak #1

Parametric Peak #1 is the pack's most opinionated node and, honestly, its most interesting. Where the other schedulers give you generic math curves, this one is a purpose-built peak shape - a curve that rises, holds a crest, and falls - with explicit warmup and decay controls for each side. The name says "Parametric Peak #1," which reads like the author has more peak shapes in the drawer; this is the first, and it's clearly designed for one job in particular.

That job is feeding ScheduledCFGGuider. The whole ComfyUI-ScheduledGuider-Ext pack exists to let you schedule CFG over the denoising run, and a peak shape is the classic answer to "what CFG curve do I actually want?" The community intuition is that guidance should ramp up after the initial structure-forming steps, hold strong through the detail-rendering middle, and ease off before the end to avoid overcooking. That's a peak. This node generates the curve.

How it works

It builds the curve in two halves. peak (default 0.25) sets where the crest sits as a fraction of the total steps - at 0.25, the curve climbs for the first quarter and decays for the rest. warmup shapes the climb: positive values make it concave (a smooth acceleration up), negative values make it convex (a fast initial rise that eases off), and 0 makes it a straight linear ramp. decay does the same job on the way down. The math underneath is cosine-based, which is why the node's warmup/decay controls range from about -1 to 2 - you're bending a cosine, not just choosing a slope.

Notice the default steps is 200, not 20 like the pack's other schedulers. That's the giveaway: you're meant to generate a high-resolution curve and feed it to a guider, which interpolates over it regardless of your actual sampling step count.

The inputs that matter

• steps (200) - curve resolution. Keep it high for a smooth CFG curve.
• peak (0.25) - where the crest lands, 0 to 1 as a fraction of steps.
• warmup (1.0) - climb shape. Concave positive, convex negative, linear at 0.
• decay (1.0) - descent shape, same convention.

Output is a SIGMAS array.

Install

Part of ComfyUI-ScheduledGuider-Ext. ComfyUI Manager - search ComfyUI-ScheduledGuider-Ext - or:

cd ComfyUI/custom_nodes
git clone https://github.com/mfg637/ComfyUI-ScheduledGuider-Ext

Restart ComfyUI. No models, no extra dependencies.

Common issues

The peak is expressed in relative terms, which trips people up: peak = 0.25 means 25% of your steps, not step 0.25. If your crest lands somewhere unexpected, that's why.

The bigger practical caveat is the one that applies to all of the pack's guider work: a peak-shaped CFG curve presupposes CFG actually does something on your model. On SD 1.5/SDXL-lineage checkpoints it's a genuinely useful shape. On guidance-distilled models that run at CFG 1 with guidance baked into the weights, a rising-then-falling curve is mostly decorative - there's no unconditional pass for it to modulate. If you're on a modern distilled checkpoint, this node is the wrong tool for the job, and no amount of peak-tuning fixes that.