sd_txt2img_tiled: Tiled diffusion sampling (MultiDiffusion)

In sd2R: Stable Diffusion Image Generation

Tiled diffusion sampling (MultiDiffusion)

Description

Generates images at any resolution using tiled sampling: at each denoising step the latent is split into overlapping tiles, each tile is denoised independently by the UNet, and results are merged with Gaussian weighting. VRAM usage is bounded by tile size, not output resolution.

Usage

sd_txt2img_tiled(
  ctx,
  prompt,
  negative_prompt = "",
  width = 2048L,
  height = 2048L,
  sample_tile_size = NULL,
  sample_tile_overlap = 0.25,
  sample_method = SAMPLE_METHOD$EULER,
  sample_steps = 20L,
  cfg_scale = 7,
  seed = 42L,
  batch_count = 1L,
  scheduler = SCHEDULER$DISCRETE,
  clip_skip = -1L,
  eta = 0,
  vae_mode = "auto",
  vae_auto_threshold = 1048576L,
  vae_tile_size = 64L,
  vae_tile_overlap = 0.25,
  vae_tile_rel_x = NULL,
  vae_tile_rel_y = NULL,
  cache_mode = c("off", "easy", "ucache"),
  cache_config = NULL
)

Arguments

ctx	SD context created by sd_ctx
prompt	Text prompt describing desired image
negative_prompt	Negative prompt (default "")
width	Target image width in pixels (can exceed model native resolution)
height	Target image height in pixels
sample_tile_size	Tile size in latent pixels (default NULL = auto from model_type: 64 for SD1/SD2, 128 for SDXL/Flux/SD3). One latent pixel = vae_scale_factor image pixels (typically 8).
sample_tile_overlap	Overlap between tiles as fraction of tile size, 0.0-0.5 (default 0.25).
sample_method	Sampling method (see SAMPLE_METHOD)
sample_steps	Number of sampling steps (default 20)
cfg_scale	Classifier-free guidance scale (default 7.0)
seed	Random seed (-1 for random)
batch_count	Number of images to generate (default 1)
scheduler	Scheduler type (see SCHEDULER)
clip_skip	Number of CLIP layers to skip (-1 = auto)
eta	Eta parameter for DDIM-like samplers
vae_mode	VAE processing mode: "normal" (no tiling), "tiled" (always tile), or "auto" (VRAM-aware: queries free GPU memory via Vulkan and compares against estimated peak VAE usage; tiles only when VRAM is insufficient). Default "auto".
vae_auto_threshold	Pixel area fallback threshold for vae_mode = "auto" when VRAM query is unavailable (no Vulkan, CPU backend, etc.). Tiling activates when width * height exceeds this value. Default 1048576L (1024x1024 pixels).
vae_tile_size	Tile size in latent pixels for tiled VAE (default 64). Ignored when vae_tile_rel_x/vae_tile_rel_y are set.
vae_tile_overlap	Overlap ratio between tiles, 0.0-0.5 (default 0.25)
vae_tile_rel_x	Relative tile width as fraction of latent width (0-1) or number of tiles (>1). NULL = use vae_tile_size. Takes priority over vae_tile_size.
vae_tile_rel_y	Relative tile height as fraction of latent height (0-1) or number of tiles (>1). NULL = use vae_tile_size. Takes priority over vae_tile_size.
cache_mode	Step caching mode: "off" (default), "easy" (EasyCache — skips redundant denoising steps), or "ucache" (UCache). Can speed up sampling 20-40% with minor quality impact.
cache_config	Optional fine-tuned cache config from sd_cache_params. Overrides cache_mode when provided.

Details

Requires tiled VAE (enabled automatically via vae_mode = "auto").

Value

List of SD images

Examples

## Not run: 
ctx <- sd_ctx("sd15.safetensors", model_type = "sd1")
imgs <- sd_txt2img_tiled(ctx, "a vast mountain landscape",
                         width = 2048, height = 1024)
sd_save_image(imgs[[1]], "landscape.png")

## End(Not run)

sd2R documentation built on March 30, 2026, 5:08 p.m.