wip: image cutline/clamp UV bounds during mesh creation

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

@@ -79,6 +79,22 @@ export interface RasterLayerProps extends CompositeLayerProps {
    */
   maxError?: number;
 
+  /**
+   * Minimum V (top edge) of the mesh in UV space [0, 1].
+   * Use to exclude rows at the top of the tile from meshing
+   * (e.g. when the tile touches lat +90° and the projection is undefined).
+   * @default 0
+   */
+  _vMin?: number;
+
+  /**
+   * Maximum V (bottom edge) of the mesh in UV space [0, 1].
+   * Use to exclude rows at the bottom of the tile from meshing
+   * (e.g. when the tile touches lat -90° and the projection is undefined).
+   * @default 1
+   */
+  _vMax?: number;
+
   /** If set, enables debug mode for visualizing the mesh and reprojection process. */
   debug?: boolean;
 
@@ -141,6 +157,8 @@ export class RasterLayer extends CompositeLayer<RasterLayerProps> {
       height,
       reprojectionFns,
       maxError = DEFAULT_MAX_ERROR,
+      _vMin,
+      _vMax,
     } = this.props;
 
     // The mesh is lined up with the upper and left edges of the raster. So if
@@ -154,6 +172,7 @@ export class RasterLayer extends CompositeLayer<RasterLayerProps> {
       reprojectionFns,
       width + 1,
       height + 1,
+      { _vMin, _vMax },
     );
     reprojector.run(maxError);
     const { indices, positions, texCoords } = reprojectorToMesh(reprojector);

packages/raster-reproject/src/delatin.ts

@@ -112,6 +112,7 @@ export class RasterReprojector {
     reprojectors: ReprojectionFns,
     width: number,
     height: number = width,
+    { _vMin = 0, _vMax = 1 }: { _vMin?: number; _vMax?: number } = {},
   ) {
     this.reprojectors = reprojectors;
     this.width = width;
@@ -131,12 +132,14 @@ export class RasterReprojector {
     this._pending = []; // triangles pending addition to queue
     this._pendingLen = 0;
 
-    // The two initial triangles cover the entire input texture in UV space, so
-    // they range from [0, 0] to [1, 1] in u and v.
+    // The two initial triangles cover the input texture UV space.
+    // _vMin/_vMax allow callers to exclude rows at the top/bottom edges
+    // (e.g. to avoid polar singularities when the tile touches lat ±90°).
     const u1 = 1;
-    const v1 = 1;
-    const p0 = this._addPoint(0, 0);
-    const p1 = this._addPoint(u1, 0);
+    const v0 = _vMin;
+    const v1 = _vMax;
+    const p0 = this._addPoint(0, v0);
+    const p1 = this._addPoint(u1, v0);
     const p2 = this._addPoint(0, v1);
     const p3 = this._addPoint(u1, v1);