[geo-layers] Fix GlobeView Mercator tile warping

modules/geo-layers/src/terrain-layer/terrain-layer.ts

@@ -19,6 +19,11 @@ import {
 import {SimpleMeshLayer} from '@deck.gl/mesh-layers';
 import type {MeshAttributes} from '@loaders.gl/schema';
 import {TerrainWorkerLoader} from '@loaders.gl/terrain';
+import {
+  MAX_LATITUDE as MAX_WEB_MERCATOR_LATITUDE,
+  lngLatToWorld,
+  worldToLngLat
+} from '@math.gl/web-mercator';
 import TileLayer, {TileLayerProps} from '../tile-layer/tile-layer';
 import type {
   Bounds,
@@ -109,6 +114,7 @@ type TerrainLoadProps = {
   elevationData: string | null;
   elevationDecoder: ElevationDecoder;
   meshMaxError: number;
+  shouldRemapTerrainMeshToWebMercatorTile?: boolean;
   signal?: AbortSignal;
 };
 
@@ -204,6 +210,7 @@ export default class TerrainLayer<ExtraPropsT extends {} = {}> extends Composite
     bounds,
     elevationDecoder,
     meshMaxError,
+    shouldRemapTerrainMeshToWebMercatorTile,
     signal
   }: TerrainLoadProps): Promise<MeshAttributes> | null {
     if (!elevationData) {
@@ -222,7 +229,16 @@ export default class TerrainLayer<ExtraPropsT extends {} = {}> extends Composite
       }
     };
     const {fetch} = this.props;
-    return fetch(elevationData, {propName: 'elevationData', layer: this, loadOptions, signal});
+    const terrain = fetch(elevationData, {
+      propName: 'elevationData',
+      layer: this,
+      loadOptions,
+      signal
+    });
+
+    return shouldRemapTerrainMeshToWebMercatorTile
+      ? terrain.then(mesh => (mesh ? remapTerrainMeshToWebMercatorTile(mesh, bounds) : mesh))
+      : terrain;
   }
 
   getTiledTerrainData(tile: TileLoadProps): Promise<MeshAndTexture> {
@@ -244,19 +260,20 @@ export default class TerrainLayer<ExtraPropsT extends {} = {}> extends Composite
       topRight = [bbox.right, bbox.top];
     }
     const bounds: Bounds = [bottomLeft[0], bottomLeft[1], topRight[0], topRight[1]];
-    const overlappedBounds = getOverlappedBounds(
-      bounds,
-      this.props.tileSize,
-      viewport instanceof GlobeViewport
-    );
-
-    const terrain = this.loadTerrain({
-      elevationData: dataUrl,
-      bounds: overlappedBounds,
-      elevationDecoder,
-      meshMaxError,
-      signal
-    });
+    const isGlobe = viewport instanceof GlobeViewport;
+    const overlappedBounds = getOverlappedBounds(bounds, this.props.tileSize, isGlobe);
+
+    const terrain =
+      this.loadTerrain({
+        elevationData: dataUrl,
+        bounds: overlappedBounds,
+        elevationDecoder,
+        meshMaxError,
+        // The terrain surface keeps its original texture and UVs; only mesh row positions are
+        // remapped from WebMercator tile spacing to lng/lat for GlobeView.
+        shouldRemapTerrainMeshToWebMercatorTile: isGlobe,
+        signal
+      }) ?? Promise.resolve(null);
     const surface = textureUrl
       ? // If surface image fails to load, the tile should still be displayed
         fetch(textureUrl, {propName: 'texture', layer: this, loaders: [], signal}).catch(_ => null)
@@ -321,10 +338,10 @@ export default class TerrainLayer<ExtraPropsT extends {} = {}> extends Composite
     const ranges = tiles
       .map(tile => tile.content)
       .filter(Boolean)
-      .map(arr => {
-        // @ts-ignore
-        const bounds = arr[0].header.boundingBox;
-        return bounds.map(bound => bound[2]);
+      .flatMap(arr => {
+        // @ts-ignore - terrain loader returns {attributes, header} shape; header is not in MeshAttributes type
+        const bounds = (arr[0] as MeshWithBoundingBox | null)?.header?.boundingBox;
+        return bounds ? [bounds.map(bound => bound[2])] : [];
       });
     if (ranges.length === 0) {
       return;
@@ -421,3 +438,46 @@ export default class TerrainLayer<ExtraPropsT extends {} = {}> extends Composite
 
 const isTileSetURL = (url: string): boolean =>
   url.includes('{x}') && (url.includes('{y}') || url.includes('{-y}'));
+
+function remapTerrainMeshToWebMercatorTile(mesh: MeshAttributes, bounds: Bounds): MeshAttributes {
+  // The terrain loader returns {attributes: MeshAttributes, header?: ...} at runtime.
+  // MeshAttributes is typed as an index type so we use a cast to access the nested fields.
+  const attrs = (mesh as any).attributes as MeshAttributes | undefined;
+  const positionAttribute = attrs?.POSITION;
+  const texCoordAttribute = attrs?.TEXCOORD_0;
+  const positions = positionAttribute?.value;
+  const texCoords = texCoordAttribute?.value;
+  if (!positions || !texCoords) {
+    return mesh;
+  }
+
+  const [, south, , north] = bounds;
+  const northY = lngLatToMercatorWorldY(north);
+  const southY = lngLatToMercatorWorldY(south);
+  const remappedPositions = new Float32Array(positions);
+
+  for (let i = 0; i < texCoords.length / 2; i++) {
+    const v = texCoords[i * 2 + 1];
+    const mercatorY = northY + (southY - northY) * v;
+    remappedPositions[i * 3 + 1] = worldToLngLat([0, mercatorY])[1];
+  }
+
+  return {
+    ...(mesh as any),
+    attributes: {
+      ...attrs,
+      POSITION: {
+        ...positionAttribute,
+        value: remappedPositions
+      }
+    }
+  } as MeshAttributes;
+}
+
+function lngLatToMercatorWorldY(latitude: number): number {
+  const clampedLatitude = Math.max(
+    -MAX_WEB_MERCATOR_LATITUDE,
+    Math.min(MAX_WEB_MERCATOR_LATITUDE, latitude)
+  );
+  return lngLatToWorld([0, clampedLatitude])[1];
+}

modules/geo-layers/src/tile-layer/tile-layer.ts

@@ -12,9 +12,11 @@ import {
   GetPickingInfoParams,
   DefaultProps,
   FilterContext,
-  _flatten as flatten
+  COORDINATE_SYSTEM,
+  _flatten as flatten,
+  _GlobeViewport
 } from '@deck.gl/core';
-import {GeoJsonLayer} from '@deck.gl/layers';
+import {BitmapLayer, GeoJsonLayer} from '@deck.gl/layers';
 import {LayersList} from '@deck.gl/core';
 
 import type {TileLoadProps, ZRange} from '../tileset-2d/index';
@@ -421,12 +423,14 @@ export default class TileLayer<DataT = any, ExtraPropsT extends {} = {}> extends
           _offset: 0,
           tile
         });
-        tile.layers = (flatten(layers, Boolean) as Layer<{tile?: Tile2DHeader}>[]).map(layer =>
-          layer.clone({
+        tile.layers = (flatten(layers, Boolean) as Layer<{tile?: Tile2DHeader}>[]).map(layer => {
+          const globeBitmapProps = this._getGlobeBitmapLayerProps(layer);
+          return layer.clone({
             tile,
+            ...globeBitmapProps,
             ...subLayerProps
-          })
-        );
+          });
+        });
       } else if (
         subLayerProps &&
         tile.layers[0] &&
@@ -440,6 +444,25 @@ export default class TileLayer<DataT = any, ExtraPropsT extends {} = {}> extends
     });
   }
 
+  private _getGlobeBitmapLayerProps(layer: Layer): Record<string, unknown> | null {
+    // BitmapLayer and subclasses draw tile imagery over lng/lat bounds. XYZ imagery is encoded
+    // in WebMercator, so default GlobeView bitmap sublayers need UV reprojection; other layer
+    // types do not share this image-coordinate contract and are left unchanged.
+    if (
+      !(this.context.viewport instanceof _GlobeViewport) ||
+      !(layer instanceof BitmapLayer) ||
+      (layer.props as Record<string, unknown>)._imageCoordinateSystem !== 'default'
+    ) {
+      return null;
+    }
+
+    return {
+      // XYZ/slippy tile imagery is Web Mercator encoded. In GlobeView, BitmapLayer
+      // positions the mesh in lng/lat, so the image needs Mercator-to-lnglat UV conversion.
+      _imageCoordinateSystem: COORDINATE_SYSTEM.CARTESIAN
+    };
+  }
+
   filterSubLayer({layer, cullRect}: FilterContext) {
     const {tile} = (layer as Layer<{tile: Tile2DHeader}>).props;
     const {modelMatrix} = this.props;

test/modules/geo-layers/terrain-layer.spec.ts

@@ -5,8 +5,14 @@
 import {test, expect} from 'vitest';
 import {generateLayerTests, testLayerAsync} from '@deck.gl/test-utils/vitest';
 import {TerrainLayer, TileLayer} from '@deck.gl/geo-layers';
+import {_GlobeView as GlobeView} from '@deck.gl/core';
 import {SimpleMeshLayer} from '@deck.gl/mesh-layers';
 import {TerrainLoader} from '@loaders.gl/terrain';
+import {
+  MAX_LATITUDE as MAX_WEB_MERCATOR_LATITUDE,
+  lngLatToWorld,
+  worldToLngLat
+} from '@math.gl/web-mercator';
 
 test('TerrainLayer', async () => {
   const testCases = generateLayerTests({
@@ -47,3 +53,83 @@ test('TerrainLayer', async () => {
     onError: err => expect(err).toBeFalsy()
   });
 });
+
+test('TerrainLayer#globe remaps WebMercator tile rows to lng/lat mesh positions', async () => {
+  const sourcePositions = new Float32Array([0, 80, 0, 0.5, 40, 0, 1, 0, 0]);
+  const sourceTexCoords = new Float32Array([0, 0, 0.5, 0.5, 1, 1]);
+  const sourceTexture = {id: 'source-texture'};
+  const tileSize = 512;
+  const bbox = {west: 0, south: 0, east: 1, north: 80};
+  const yPad = ((bbox.north - bbox.south) / tileSize) * 1;
+  const overlappedSouth = bbox.south - yPad;
+  const overlappedNorth = bbox.north + yPad;
+  const expectedMiddleLatitude = worldToLngLat([
+    0,
+    (lngLatToMercatorWorldY(overlappedNorth) + lngLatToMercatorWorldY(overlappedSouth)) / 2
+  ])[1];
+
+  const sourceMesh = {
+    attributes: {
+      POSITION: {value: sourcePositions, size: 3},
+      TEXCOORD_0: {value: sourceTexCoords, size: 2}
+    }
+  };
+  const layer = new TerrainLayer({
+    id: 'terrain-globe-mercator',
+    elevationData: 'terrain/{z}/{x}/{y}.png',
+    texture: 'texture/{z}/{x}/{y}.png',
+    tileSize,
+    fetch: (_url, context) =>
+      Promise.resolve(context.propName === 'texture' ? sourceTexture : sourceMesh)
+  });
+  layer.context = {
+    viewport: new GlobeView().makeViewport({
+      width: 512,
+      height: 512,
+      viewState: {
+        longitude: 0,
+        latitude: 0,
+        zoom: 1
+      }
+    })
+  };
+  layer.state = {isTiled: true};
+
+  const [mesh, texture] = await layer.getTiledTerrainData({
+    index: {x: 0, y: 0, z: 1},
+    id: '0-0-1',
+    bbox,
+    zoom: 1
+  });
+  const positions = mesh!.attributes.POSITION.value;
+
+  expect(positions, 'remap copies the loader positions').not.toBe(sourcePositions);
+  expect(mesh!.attributes.TEXCOORD_0.value, 'remap preserves source texture coordinates').toBe(
+    sourceTexCoords
+  );
+  expect(texture, 'terrain surface texture is passed through').toBe(sourceTexture);
+  expect(sourcePositions[1], 'source top row is unchanged').toBe(80);
+  expect(sourcePositions[4], 'source middle row is unchanged').toBe(40);
+  expect(sourcePositions[7], 'source bottom row is unchanged').toBe(0);
+
+  expect(positions[1], 'top row latitude follows the overlapped tile north').toBeCloseTo(
+    overlappedNorth,
+    5
+  );
+  expect(positions[4], 'middle row uses Mercator latitude instead of linear latitude').toBeCloseTo(
+    expectedMiddleLatitude,
+    5
+  );
+  expect(positions[7], 'bottom row latitude follows the overlapped tile south').toBeCloseTo(
+    overlappedSouth,
+    5
+  );
+});
+
+function lngLatToMercatorWorldY(latitude: number): number {
+  const clampedLatitude = Math.max(
+    -MAX_WEB_MERCATOR_LATITUDE,
+    Math.min(MAX_WEB_MERCATOR_LATITUDE, latitude)
+  );
+  return lngLatToWorld([0, clampedLatitude])[1];
+}