perf(raster-tileset): Reduce re-renders of RasterLayer for same per-tile transforms

packages/deck.gl-raster/src/raster-tile-layer/raster-tile-layer.ts

@@ -380,12 +380,9 @@ export class RasterTileLayer<
       return debugLayers;
     }
 
-    const { x, y, z } = tile.index;
-    const level = descriptor.levels[z];
-    if (!level) {
-      return debugLayers;
-    }
-    const { forwardTransform, inverseTransform } = level.tileTransform(x, y);
+    // Access forwardTransform/inverseTransform from tile metadata so that
+    // reference equality holds across renders.
+    const { forwardTransform, inverseTransform } = tile;
     const tileResult = renderTile(props.data);
     if (!tileResult) {
       return debugLayers;

packages/deck.gl-raster/src/raster-tileset/raster-tileset-2d.ts

@@ -21,6 +21,7 @@ import type {
   Bounds,
   Corners,
   ProjectedBoundingBox,
+  ProjectionFunction,
   TileIndex,
   ZRange,
 } from "./types.js";
@@ -55,6 +56,24 @@ export type TileMetadata = {
    * Tile height in pixels.
    */
   tileHeight: number;
+
+  /**
+   * Forward (tile-local pixel → CRS) transform for this tile.
+   *
+   * Stable across the tile's lifetime; computed once at tile creation. Stored
+   * on the tile so downstream layers (e.g. `RasterTileLayer._renderSubLayers`)
+   * receive a reference-stable function across renders, which is what
+   * `RasterLayer`'s `reprojectionFnsChanged` check needs to avoid spurious mesh
+   * regeneration.
+   */
+  forwardTransform: ProjectionFunction;
+
+  /**
+   * Inverse (CRS → tile-local pixel) transform.
+   *
+   * Same stability guarantees as {@link TileMetadata.forwardTransform}.
+   */
+  inverseTransform: ProjectionFunction;
 };
 
 /**
@@ -253,6 +272,9 @@ export class RasterTileset2D extends Tileset2D {
       ...projectedBounds,
     );
 
+    const { forwardTransform, inverseTransform } =
+      levelDescriptor.tileTransform(x, y);
+
     return {
       bbox: {
         west,
@@ -269,6 +291,8 @@ export class RasterTileset2D extends Tileset2D {
       projectedCorners,
       tileWidth,
       tileHeight,
+      forwardTransform,
+      inverseTransform,
     };
   }
 }

packages/deck.gl-raster/tests/raster-tileset/raster-tileset-2d-tile-transform.test.ts

@@ -0,0 +1,53 @@
+import type { _Tileset2DProps as Tileset2DProps } from "@deck.gl/geo-layers";
+import { compose, scale, translation } from "@developmentseed/affine";
+import { describe, expect, it } from "vitest";
+import { AffineTileset } from "../../src/raster-tileset/affine-tileset.js";
+import { AffineTilesetLevel } from "../../src/raster-tileset/affine-tileset-level.js";
+import { RasterTileset2D } from "../../src/raster-tileset/raster-tileset-2d.js";
+
+const identity = (x: number, y: number): [number, number] => [x, y];
+
+const PROJECTIONS = {
+  projectTo3857: identity,
+  projectFrom3857: identity,
+  projectTo4326: identity,
+  projectFrom4326: identity,
+};
+
+function tilesetProps(): Tileset2DProps {
+  return { getTileData: () => new Promise(() => {}) } as Tileset2DProps;
+}
+
+describe("RasterTileset2D.getTileMetadata", () => {
+  it("attaches per-tile forwardTransform/inverseTransform to TileMetadata", () => {
+    const level = new AffineTilesetLevel({
+      affine: compose(translation(100, 200), scale(10, -10)),
+      arrayWidth: 8,
+      arrayHeight: 8,
+      tileWidth: 4,
+      tileHeight: 4,
+      mpu: 1,
+    });
+    const descriptor = new AffineTileset({
+      levels: [level],
+      ...PROJECTIONS,
+    });
+    const tileset = new RasterTileset2D(tilesetProps(), descriptor);
+
+    const metadata = tileset.getTileMetadata({ x: 1, y: 1, z: 0 });
+
+    expect(typeof metadata.forwardTransform).toBe("function");
+    expect(typeof metadata.inverseTransform).toBe("function");
+
+    // Tile (1,1) at pixel (0,0) should map to the CRS origin of that tile.
+    // Tile is 4x4 pixels at 10 CRS units/pixel from origin (100, 200), Y flipped.
+    const [x, y] = metadata.forwardTransform(0, 0);
+    expect(x).toBeCloseTo(140, 10);
+    expect(y).toBeCloseTo(160, 10);
+
+    // Round-trip via inverseTransform.
+    const [px, py] = metadata.inverseTransform(x, y);
+    expect(px).toBeCloseTo(0, 10);
+    expect(py).toBeCloseTo(0, 10);
+  });
+});