Generate Controlled Video with ComfyUI

Symptom	Cause	Fix
Generated 3D object has a clean silhouette but messy textures	Source image had a complex or cluttered background, strong directional shadows, or a non-ideal framing	Use 1:1 aspect ratio images with a plain or removed background, neutral even lighting, and a clear front-facing or three-quarter view; pre-remove busy backgrounds before TRELLIS
3D object geometry or texture quality is low	Sparse Structure / Latent Sampling steps or CFG too low for the prompt	Raise Sparse Structure Sampling Steps for cleaner topology; raise Latent Sampling Steps for surface detail; increase CFG on both; start from defaults and increase if the output does not match the prompt
SANA previews are slow or lower quality than expected	Preview resolution not matched to SANA’s sweet spot	Use 1024×1024 for quality; use 512 or 768 for faster iteration previews
Need faster image iteration than FLUX.1	Full FLUX.1 Depth path is heavier than needed for early layout tests	In the Load Model node, try a smaller model such as SDXL; use positive/negative prompts and Wildcards in the ComfyUI graph for lighting variation
LTX-2.3 output looks soft or takes too long while iterating	Resolution or frame count too high for draft passes	Iterate at 1280×720 (or 1280×704) and keep sequences under 257 frames; raise to 1920×1088 when ready for final quality
LTX motion ignores the prompt or looks unnatural	Guidance / step settings out of a useful range	Use 20–30 steps while iterating and 40+ for finals; set Guidance Scale around 3.0–3.5
Last frame does not match the provided end image	End-frame guide strength or timing too weak; long clips degrade end-frame adherence	Raise last-frame strength to 1.0; try last-frame position index `-12` instead of `-1`; keep sequences near 5 seconds (121 frames)
Output video is completely black	Invalid frame count, missing crop guides, or missing text encoder	Use frame counts that follow `(N×8)+1` (49, 65, 97, 121, …); for FirstFrame/LastFrame workflows add LTXVCropGuides before VAE decode; confirm the Gemma text encoder loaded
Subject appearance drifts mid-video	Model limitation on long or multi-motion clips	Keep clips to about 5 seconds; describe one clear motion; reduce CFG to about 3.0–3.5; for recurring characters, a subject LoRA improves consistency
Upscale quality or speed is off	Upscale factor or quality level not matched to source resolution	Set Upscale Factor 1–4 from input size to target (for ~720p→4K use 3); set Quality Level to 4 for maximum edge sharpening unless you need speed
Prompt or negative prompt fights the keyframes	Prompt restates what is already in the images, or negative list is too long	Describe change and motion, not the static look; keep negatives focused (for example: morphing, distortion, warping, flicker, jitter, blur, artifacts); LTX-2.3 does not require a negative prompt
GPU out-of-memory or very slow generation	Workload exceeds dedicated VRAM, or other GPU apps are running	Close other GPU applications; lower resolution, frame count, or upscale factor; monitor with Task Manager / GPU tools on Windows

NOTE

On discrete-GPU hardware platforms, GPU memory is separate from system RAM. Out-of-memory usually means the workload exceeds VRAM: reduce resolution, frame count, or concurrent apps. Confirm no other process is holding GPU memory before retrying.

For latest known issues, see the documentation linked under Resources for your hardware platform.