91 lines
4.5 KiB
Markdown
91 lines
4.5 KiB
Markdown
# FunPack Hybrid Euler 2S Sampler
|
|
|
|
This node outputs a ComfyUI `SAMPLER` and can also take optional `SIGMAS` input and output modified `SIGMAS` for use with `CustomSamplerAdvanced` / `SamplerCustomAdvanced`.
|
|
|
|
## Purpose
|
|
|
|
It is designed as a quality/speed compromise between:
|
|
|
|
- `euler_ancestral`: fast, reliable, one model evaluation per step
|
|
- deterministic 2S-style ODE refinement: higher quality, but more expensive because it needs extra evaluations
|
|
|
|
This sampler keeps classic Euler ancestral for the early "structure building" stage where motion, anatomy and main composition are forming. On the late denoise steps it switches to a deterministic Euler / DPM-Solver++(2S) ODE refinement path where fine detail and cleanup usually matter most.
|
|
|
|
It can also build an optional paper-style Restart schedule at the progress point you choose:
|
|
|
|
- detect a restart anchor across the full sigma schedule
|
|
- insert upward sigma jumps back to a higher sigma
|
|
- replay the chosen sigma interval one or more times
|
|
|
|
Unlike the older implementation, Restart is now encoded directly into the outgoing `SIGMAS` schedule, so the visible schedule passed into `SamplerCustomAdvanced` is the actual schedule that gets executed.
|
|
|
|
## Recommended wiring
|
|
|
|
Use this node with `SamplerCustomAdvanced` or `CustomSamplerAdvanced`:
|
|
|
|
- connect your base scheduler output into this node's optional `sigmas` input
|
|
- connect this node's `sampler` output into the sampler input
|
|
- connect this node's `sigmas` output into the sigmas input
|
|
|
|
This node is not intended for `KSampler`.
|
|
|
|
## Parameters
|
|
|
|
**eta**: Ancestral stochasticity. `1.0` keeps normal ancestral behavior.
|
|
|
|
**s_noise**: Noise multiplier for ancestral noise injection.
|
|
|
|
**high_quality_pct**: Fraction of the *late* denoise steps that switch from Euler ancestral into deterministic quality refinement.
|
|
Example: `0.35` means only the last 35% of steps use the ODE refinement path.
|
|
|
|
**correction_blend**: Blend between late-step Euler ODE and late-step 2S correction.
|
|
|
|
- `0.0` = pure late-step Euler ODE
|
|
- `1.0` = full late-step DPM++(2S)-style correction
|
|
|
|
**restart_steps**: Target size of the restarted sigma interval. The node interprets this against the actual sigma curve and expands the outgoing `SIGMAS` schedule accordingly.
|
|
|
|
**restart_repeats**: How many Restart loops to run. `0` disables Restart.
|
|
|
|
**restart_trigger_pct**: Sampling progress point where Restart is triggered across the full schedule. This is independent from `high_quality_pct`, so values such as `0.30` can trigger an early restart instead of being clamped to the Euler-to-2S transition point.
|
|
|
|
**restart_noise**: Noise strength used when re-noising the latent up to the restart interval's higher sigma.
|
|
|
|
**sigmas**: Optional incoming sigma schedule. If connected, the node outputs a restart-expanded sigma schedule that matches the sampler settings. If not connected, the sampler output still works, but there is no schedule for the node to rewrite.
|
|
|
|
## Recommended starting values
|
|
|
|
- `eta = 1.0`
|
|
- `s_noise = 1.0`
|
|
- `high_quality_pct = 0.30` to `0.40`
|
|
- `correction_blend = 1.0`
|
|
- `restart_repeats = 0` for baseline testing
|
|
|
|
For a first Restart test, try:
|
|
|
|
- `high_quality_pct = 0.35`
|
|
- `correction_blend = 1.0`
|
|
- `restart_steps = 3`
|
|
- `restart_repeats = 1`
|
|
- `restart_trigger_pct = 0.85`
|
|
- `restart_noise = 1.0`
|
|
|
|
Example: with `8` base sampling steps, `restart_steps = 3`, and `restart_repeats = 1`, a normal evenly spaced schedule will usually expand into a schedule with about `3` extra restart transitions. With custom sigmas, the exact replay step count can shift slightly because Restart is anchored to the real sigma values rather than raw step indices.
|
|
|
|
## Expected behavior
|
|
|
|
Compared to plain `euler_ancestral`, this sampler should usually:
|
|
|
|
- preserve more late-stage detail
|
|
- clean up texture and edge quality better
|
|
- keep the early motion/anatomy formation more lively
|
|
- cost less than running a heavier deterministic solver for the whole schedule
|
|
|
|
With Restart enabled, it may further improve late cleanup and detail consistency, but it will increase runtime and may be too aggressive for some video workflows if overused.
|
|
|
|
Because Restart is now represented in the outgoing `SIGMAS`, the total number of executed transitions should match what the expanded schedule shows in the downstream custom sampler.
|
|
|
|
## Limitation
|
|
|
|
This node improves the **sampler-side quality/speed tradeoff**. It does **not** reduce the underlying cost of CFG++ guidance itself. If the goal becomes specifically "CFG++ quality at lower guidance cost", that likely requires a custom `GUIDER`, not just a custom `SAMPLER`.
|