HiDiffusion

HiDiffusion is an optional denoising enhancement that can improve detail and structure at higher resolutions for SD 1.5, SD 2.1, and SDXL. It modifies the UNet during denoising and is most noticeable at 1536px and above.

The vendored implementation includes module-key definitions for SD 1.5 and SDXL. SD 2.1 intentionally reuses the SD 1.5 module-key mapping.

Learn more: https://github.com/megvii-research/HiDiffusion

Where to find the switches

1. Open the Canvas tab.
2. Expand Advanced Settings.
3. In the Advanced grid, enable HiDiffusion and optionally adjust the two sub‑toggles and ratios:

• HiDiffusion: RAU‑Net
  • HiDiffusion: Window Attention
  • HiDiffusion: T1 Ratio
  • HiDiffusion: T2 Ratio

What the switches do

• HiDiffusion: Enables the HiDiffusion patch for denoising. Use this for high‑resolution generations; the effect is subtle at lower sizes.

• HiDiffusion: RAU‑Net: Enables RAU‑Net blocks. This typically improves structure and mid‑frequency detail, especially at larger resolutions.

• HiDiffusion: Window Attention: Enables windowed attention blocks. This can boost local texture/detail, but may slightly affect global coherence in some prompts.

• HiDiffusion: T1 Ratio: Controls when HiDiffusion switches into its mid‑stage behavior. Lower values switch earlier; higher values preserve global structure longer.

• HiDiffusion: T2 Ratio: Controls when HiDiffusion switches into its late‑stage behavior. Higher values keep window attention active longer and can sharpen local detail.

Tips

• Try 1536–2048 px for the clearest benefits (SDXL).
• If results look worse, disable Window Attention first, then RAU‑Net.
• Effects vary by scheduler and model; compare with the same seed for a fair test.