# Texture Tile Seam Checker

> Measure opposite-edge jumps and feather a reusable numeric texture tile. Turn a typed grayscale grid into a texture tile, compare opposite-edge differences before and after symmetric feathering, and inspect an exact 2 × 2 repeated PNG. Save an editable material project with its original source and blend recipe.

Part of usefulweb.app (https://usefulweb.app/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://renderloomtileseam.usefulweb.app/ (interactive tool at https://renderloomtileseam.usefulweb.app/tool)
- JSON API: POST https://renderloomtileseam.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://renderloomtileseam.usefulweb.app/api/v1/tool)
- OpenAPI: https://renderloomtileseam.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://renderloomtileseam.usefulweb.app/mcp - tool `renderloom_tile_seam`

## Inputs
- grid (textarea): Height grid (0–1, rows separated by newlines)
- size (integer): Square map size (px)
- seamBlend (number): Edge feather fraction

## Method
- Input is a 2–64 row and column grid of 0–1 heights, bilinearly interpolated to 16–512 px. The same deterministic engine is used in the browser Texture Lab and API/MCP.
- The edge score is the mean absolute RGB difference between corresponding first/last rows and columns, divided by 255. A score of zero means outer pixels match exactly; it is not a perceptual quality score.
- A blend band of 0–25% per edge symmetrically mixes corresponding edge pairs toward their average. Weight is (1 − distance / band width)². Horizontal blending precedes vertical blending. Pixels outside the bands are unchanged.
- The 2 × 2 preview repeats the blended tile without interpolation. Feathering can soften edge detail and cannot remove repeated motifs or guarantee continuity of derivatives.

## Limits
- Equal boundary colors do not guarantee matching slopes or an invisible repeating pattern. This is symmetric edge feathering, not texture synthesis.