SamplerRES_Momentumized

SamplerRES_Momentumized is the pack's take on the Refined Exponential Solver (RES) - the same family of exponential-integrator samplers that RES4LYF made famous on the flow-matching scene - with a momentum term bolted on. It's from ComfyUI Extra Samplers by Clybius, credits Kat and Birch-San for the underlying source, and outputs a SAMPLER for custom sampling.

RES-family solvers are the "fancy math" branch of samplers: instead of the plain Euler step, they use exponential-integrator corrections (phi functions of the log-sigma step, the source is full of expm1 terms) to get higher-order accuracy per step. That's why these solvers became the 2026 poster children for high-quality low-step generation - the knowledge base tracks RES4LYF out-mentioning DPM++ 2M Karras in community threads by four to one. The "Momentumized" part here is the pack's own addition: a momentum term (default 0.5, range −1 to 1) that mixes in the previous step's update direction, so the trajectory carries memory between steps instead of starting fresh each time. Positive momentum smooths the path; negative can introduce oscillation. It's a "somewhat naively momentumized" modification by the author's own admission - which is to say, tune with a fixed seed and your own eyes.

The inputs that matter:

• momentum - the pack's addition. Default 0.5; try 0.1–0.5 to start, and only push into negative territory if you're deliberately hunting for variety.
• denoise_to_zero (default on) - whether the solver drives the last step fully to clean output.
• ita (default 0.25) - the solver's internal coefficient; the phi correction strength.
• c2 (default 0.5) - the second-stage coefficient in the two-stage RES update. Both ita and c2 are "leave alone until you've read the solver" knobs.
• simple_phi_calc (default off) - a simpler approximation of the exponential correction terms; can help edge cases at the cost of accuracy.
• noise_sampler_type - the pack's usual menu of noise samplers.

Output: a SAMPLER for your custom sampling chain.

Here's the context that decides when to use it: RES-family solvers are the ones people actually praise on flow-matching models, so unlike the pack's ODE-heavy oddities this isn't a DDPM-only toy. But the knowledge base's caution still applies - the momentum modification is the pack's own experiment, and the community's sweeps show exotic high-order solvers can fall apart on straight trajectories if the schedule fights you. Conservative schedule, moderate steps, momentum near the default, and you're in a good place.

Install is the shared pack routine - ComfyUI Manager → "ComfyUI Extra Samplers", or:

cd ComfyUI/custom_nodes
git clone https://github.com/Clybius/ComfyUI-Extra-Samplers

then restart. No model downloads; dependency kornia.