olivv-cs-ComfyUI-FunPack/docs/FunPackHybridEuler2SSampler.md

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 apply optional early/mid motion pulses for single-clip image-to-video workflows. These pulses add monotonic noise kicks at selected normal denoise steps instead of inserting upward sigma jumps. This is intended to push LTX2.3 away from stale frame-1 reference stiffness while avoiding the audio damage caused by Restart replay.

Restart replay has been removed because upward sigma replay can break LTX audio generation.

For hard viewpoint or scene-context resets, use FunPack Context Transition Windows before sampling. That node changes which frames the model can see in each denoise evaluation; this sampler only changes the denoise trajectory.

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

motion_pulse_mode: Anti-stiffness motion pulse preset:

• off: preserve legacy sampler behavior.
• balanced: one moderate early/mid pulse.
• aggressive: at least two stronger early/mid pulses for stale image-to-video generations.
• custom: use the transition count, spacing, and strength exactly as configured.

motion_pulse_start_pct: Sampling progress point where the first motion pulse is applied.

motion_pulse_count: Number of requested early/mid motion pulses. Pulses that would land in the late quality phase are skipped.

motion_pulse_spacing_pct: Progress spacing between motion pulses.

motion_pulse_strength: Strength of the monotonic noise kick. Higher values push harder against stale image references, with more drift risk.

velocity_bias_mode: Experimental early velocity steering mode:

• off: preserve legacy sampler behavior.
• capture: save averaged early velocity directions around normalized sigma 0.9 and 0.8.
• apply: apply a previously captured matching bias.
• capture_and_apply: do both in one run.

velocity_bias_strength: Strength for applying captured early velocity bias. Keep this low; 0.0 disables the applied delta.

velocity_refinement_key: In-memory key used to group captured velocity directions.

velocity_aspect_bucket: Optional grouping value such as landscape, portrait, square, ultrawide, or vertical.

sigmas: Optional incoming sigma schedule. If connected, the node returns the same monotonic schedule plus sampler-side metadata for motion pulses. If not connected, the sampler computes pulse positions from the runtime schedule.

Recommended starting values

• eta = 1.0
• s_noise = 1.0
• high_quality_pct = 0.30 to 0.40
• correction_blend = 1.0
• motion_pulse_mode = off for baseline testing
• velocity_bias_mode = off unless you are deliberately testing captured good-run steering

For an aggressive LTX2.3 image-to-video motion test, try:

• high_quality_pct = 0.35
• correction_blend = 1.0
• motion_pulse_mode = aggressive
• motion_pulse_start_pct = 0.30
• motion_pulse_count = 2
• motion_pulse_spacing_pct = 0.22
• motion_pulse_strength = 0.85

Keep the prompt/refiner conditioning explicit about both action and camera change, for example orbiting camera, dolly in, zoom out, new side angle, turning, or dynamic pose change.

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 motion pulses enabled, it should more strongly encourage action, camera movement, and viewpoint changes inside a single clip. Stronger settings can increase subject drift or visual instability.

The outgoing SIGMAS remain monotonic. Motion pulses happen inside the sampler at selected denoise steps rather than by expanding the schedule.

Velocity bias memory is process-local and experimental. Capture only runs you consider good references, then apply with the same refinement key, aspect bucket, and latent shape. Incompatible shapes are ignored.

If you need the model to stop carrying the previous segment's temporal context forward, add FunPack Context Transition Windows. It is the stronger transition tool and should be preferred for multi-view or "scene reset" testing.

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.