Fix lands for MiniMax H3 VAE grid artifacts in ComfyUI via PR #16422
marres · reddit · 2026-09-21
The author tracked down the rectangular grid/tile-seam artifact when decoding MiniMax H3 video in ComfyUI and fixed it in PR #16422.
Root cause: the H3 VAE decodes large frames in overlapping spatial tiles, but ComfyUI's compositor blended tiles pairwise, dropping contributors at overlap intersections — creating discontinuities aligned with the tile layout.
Fix: normalized overlap-add across all contributing tiles. The VAE itself is untouched (same decoder windows, overlap geometry, temporal decoding); no blur or post-processing.
Cost: 121 MiB extra FP32 composition scratch for a 1216×896 multi-frame decode (bounded scratch, not a full-frame copy) plus some blending math; no extra VAE decoder calls. Regression tests and CI pass.
Try it:
bash
git fetch https://github.com/Comfy-Org/ComfyUI.git pull/16422/head:pr-16422
git switch pr-16422
Restart ComfyUI; existing workflows keep using the native VAEDecode node. Manual checkout won't be needed once merged.
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