fix: resolve overlapping group bounding boxes and add README

Group 4/5 and Group 1/2 bounding boxes overlapped, causing nodes to
appear in multiple groups. Muting the Seam Fix group would have also
muted Pass 1 output nodes. Repositioned GenerateSeamMask node and
adjusted all group boundaries to eliminate overlaps.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -0,0 +1,54 @@
+# ComfyUI_UltimateSGUpscale
+
+Tiled upscaling for ComfyUI using built-in nodes. Replicates the core features of [UltimateSDUpscale](https://github.com/ssitu/ComfyUI_UltimateSDUpscale) as a transparent workflow you can inspect and modify.
+
+## Requirements
+
+- ComfyUI with `SplitImageToTileList` and `ImageMergeTileList` nodes (added in [PR #12599](https://github.com/comfyanonymous/ComfyUI/pull/12599))
+
+## Installation
+
+Clone into your ComfyUI `custom_nodes` directory:
+
+```bash
+cd ComfyUI/custom_nodes
+git clone https://github.com/ethanfel/ComfyUI_UltimateSGUpscale.git
+```
+
+This installs one custom node (`Generate Seam Mask`) and provides an example workflow.
+
+## What's Included
+
+### Example Workflow
+
+`example_workflows/tiled-upscale-builtin-nodes.json` — a two-pass tiled upscaling workflow:
+
+**Pass 1 — Tiled Redraw:** Upscales the image with a model (e.g. 4x-UltraSharp), splits it into overlapping tiles, runs each tile through KSampler, then merges them back with sine-based blending.
+
+**Pass 2 — Seam Fix (optional):** Generates a mask targeting only the seam regions between tiles, then runs a second tiled denoise pass restricted to those seam bands via `SetLatentNoiseMask`. Mute or bypass the "Seam Fix" group to skip this pass.
+
+### Generate Seam Mask Node
+
+A small helper node that creates a binary mask image with white bands at tile seam positions. It replicates `SplitImageToTileList`'s tiling logic to place bands at the exact center of each overlap region.
+
+**Inputs:**
+| Parameter | Default | Description |
+|-----------|---------|-------------|
+| image_width | 2048 | Image width (connect from GetImageSize) |
+| image_height | 2048 | Image height (connect from GetImageSize) |
+| tile_width | 1024 | Tile width matching Pass 1 |
+| tile_height | 1024 | Tile height matching Pass 1 |
+| overlap | 128 | Overlap matching Pass 1 |
+| seam_width | 64 | Width of seam bands in pixels |
+
+**Output:** `IMAGE` — a mask with white bands at seam positions, black elsewhere.
+
+## How It Works
+
+The workflow chains standard ComfyUI nodes together. `SplitImageToTileList` outputs a list, and ComfyUI's auto-iteration runs all downstream nodes (VAEEncode, KSampler, VAEDecode) once per tile automatically. Scalar inputs (model, conditioning, VAE) are reused across tiles. `ImageMergeTileList` reassembles tiles using sine-weighted blending for smooth overlap transitions.
+
+The seam fix pass uses `SetLatentNoiseMask` to restrict denoising to only the masked seam regions, leaving the rest of the image untouched.
+
+## License
+
+MIT

example_workflows/tiled-upscale-builtin-nodes.json

@@ -235,7 +235,7 @@
     {
       "id": 13,
       "type": "GenerateSeamMask",
-      "pos": [2040, 500],
+      "pos": [2370, 650],
       "size": [250, 170],
       "flags": {},
       "order": 12,
@@ -453,7 +453,7 @@
     {
       "id": 1,
       "title": "Load Models",
-      "bounding": [40, 130, 345, 400],
+      "bounding": [40, 130, 345, 190],
       "color": "#3f789e",
       "font_size": 24,
       "flags": {}
@@ -477,7 +477,7 @@
     {
       "id": 4,
       "title": "Pass 1: Tiled Redraw",
-      "bounding": [1150, 130, 970, 730],
+      "bounding": [1150, 130, 1200, 730],
       "color": "#3a7e3a",
       "font_size": 24,
       "flags": {}
@@ -485,7 +485,7 @@
     {
       "id": 5,
       "title": "Pass 2: Seam Fix (bypass/mute to skip)",
-      "bounding": [2030, 130, 1800, 600],
+      "bounding": [2360, 130, 1470, 710],
       "color": "#7e3a3a",
       "font_size": 24,
       "flags": {}