fix(GeoArrow): handle tessellation error & improve mean centers (#2803)

modules/arrow/src/geoarrow/convert-geoarrow-to-binary-geometry.ts

@@ -8,6 +8,15 @@ import {GeoArrowEncoding} from '@loaders.gl/gis';
 import {updateBoundsFromGeoArrowSamples} from './get-arrow-bounds';
 import {TypedArray} from '@loaders.gl/loader-utils';
 
+/**
+ * Binary geometry type
+ */
+enum BinaryGeometryType {
+  points = 'points',
+  lines = 'lines',
+  polygons = 'polygons'
+}
+
 /**
  * Binary data from geoarrow column and can be used by e.g. deck.gl GeojsonLayer
  */
@@ -57,7 +66,9 @@ export type BinaryGeometriesFromArrowOptions = {
   /** option to specify which chunk to get binary geometries from, for progressive rendering */
   chunkIndex?: number;
   /** option to get mean centers from geometries, for polygon filtering */
-  meanCenter?: boolean;
+  calculateMeanCenters?: boolean;
+  /** option to compute the triangle indices by tesselating polygons */
+  triangulate?: boolean;
 };
 
 /**
@@ -86,7 +97,7 @@ export function getBinaryGeometriesFromArrow(
 
   chunks.forEach((chunk) => {
     const {featureIds, flatCoordinateArray, nDim, geomOffset, triangles} =
-      getBinaryGeometriesFromChunk(chunk, geoEncoding);
+      getBinaryGeometriesFromChunk(chunk, geoEncoding, options);
 
     const globalFeatureIds = new Uint32Array(featureIds.length);
     for (let i = 0; i < featureIds.length; i++) {
@@ -145,7 +156,7 @@ export function getBinaryGeometriesFromArrow(
     binaryGeometries,
     bounds,
     featureTypes,
-    ...(options?.meanCenter
+    ...(options?.calculateMeanCenters
       ? {meanCenters: getMeanCentersFromBinaryGeometries(binaryGeometries)}
       : {})
   };
@@ -159,21 +170,22 @@ export function getBinaryGeometriesFromArrow(
 export function getMeanCentersFromBinaryGeometries(binaryGeometries: BinaryFeatures[]): number[][] {
   const globalMeanCenters: number[][] = [];
   binaryGeometries.forEach((binaryGeometry: BinaryFeatures) => {
-    let binaryGeometryType: string | null = null;
+    let binaryGeometryType: keyof typeof BinaryGeometryType | null = null;
     if (binaryGeometry.points && binaryGeometry.points.positions.value.length > 0) {
-      binaryGeometryType = 'points';
+      binaryGeometryType = BinaryGeometryType.points;
     } else if (binaryGeometry.lines && binaryGeometry.lines.positions.value.length > 0) {
-      binaryGeometryType = 'lines';
+      binaryGeometryType = BinaryGeometryType.lines;
     } else if (binaryGeometry.polygons && binaryGeometry.polygons.positions.value.length > 0) {
-      binaryGeometryType = 'polygons';
+      binaryGeometryType = BinaryGeometryType.polygons;
     }
 
     const binaryContent = binaryGeometryType ? binaryGeometry[binaryGeometryType] : null;
     if (binaryContent && binaryGeometryType !== null) {
       const featureIds = binaryContent.featureIds.value;
       const flatCoordinateArray = binaryContent.positions.value;
       const nDim = binaryContent.positions.size;
-      const primitivePolygonIndices = binaryContent.primitivePolygonIndices?.value;
+      const primitivePolygonIndices =
+        binaryContent.type === 'Polygon' ? binaryContent.primitivePolygonIndices?.value : undefined;
 
       const meanCenters = getMeanCentersFromGeometry(
         featureIds,
@@ -201,30 +213,33 @@ function getMeanCentersFromGeometry(
   featureIds: TypedArray,
   flatCoordinateArray: TypedArray,
   nDim: number,
-  geometryType: string,
+  geometryType: keyof typeof BinaryGeometryType,
   primitivePolygonIndices?: TypedArray
 ) {
   const meanCenters: number[][] = [];
   const vertexCount = flatCoordinateArray.length;
   let vertexIndex = 0;
+  let coordIdx = 0;
+  let primitiveIdx = 0;
   while (vertexIndex < vertexCount) {
     const featureId = featureIds[vertexIndex / nDim];
     const center = [0, 0];
     let vertexCountInFeature = 0;
-    while (vertexIndex < vertexCount && featureIds[vertexIndex / nDim] === featureId) {
+    while (vertexIndex < vertexCount && featureIds[coordIdx] === featureId) {
       if (
-        geometryType === 'polygons' &&
-        primitivePolygonIndices &&
-        primitivePolygonIndices.indexOf(vertexIndex / nDim) >= 0
+        geometryType === BinaryGeometryType.polygons &&
+        primitivePolygonIndices?.[primitiveIdx] === coordIdx
       ) {
         // skip the first point since it is the same as the last point in each ring for polygons
         vertexIndex += nDim;
+        primitiveIdx++;
       } else {
         center[0] += flatCoordinateArray[vertexIndex];
         center[1] += flatCoordinateArray[vertexIndex + 1];
         vertexIndex += nDim;
         vertexCountInFeature++;
       }
+      coordIdx += 1;
     }
     center[0] /= vertexCountInFeature;
     center[1] /= vertexCountInFeature;
@@ -237,11 +252,13 @@ function getMeanCentersFromGeometry(
  * get binary geometries from geoarrow column
  * @param chunk one chunk/batch of geoarrow column
  * @param geoEncoding geo encoding of the geoarrow column
+ * @param options options for getting binary geometries
  * @returns BinaryGeometryContent
  */
 function getBinaryGeometriesFromChunk(
   chunk: arrow.Data,
-  geoEncoding: GeoArrowEncoding
+  geoEncoding: GeoArrowEncoding,
+  options?: BinaryGeometriesFromArrowOptions
 ): BinaryGeometryContent {
   switch (geoEncoding) {
     case 'geoarrow.point':
@@ -252,7 +269,7 @@ function getBinaryGeometriesFromChunk(
       return getBinaryLinesFromChunk(chunk, geoEncoding);
     case 'geoarrow.polygon':
     case 'geoarrow.multipolygon':
-      return getBinaryPolygonsFromChunk(chunk, geoEncoding);
+      return getBinaryPolygonsFromChunk(chunk, geoEncoding, options);
     default:
       throw Error('invalid geoarrow encoding');
   }
@@ -271,47 +288,62 @@ export function getTriangleIndices(
   primitivePolygonIndices: Int32Array,
   flatCoordinateArray: Float64Array,
   nDim: number
-): Uint32Array {
-  let primitiveIndex = 0;
-  const triangles: number[] = [];
-  // loop polygonIndices to get triangles
-  for (let i = 0; i < polygonIndices.length - 1; i++) {
-    const startIdx = polygonIndices[i];
-    const endIdx = polygonIndices[i + 1];
-    // get subarray of flatCoordinateArray
-    const slicedFlatCoords = flatCoordinateArray.subarray(startIdx * nDim, endIdx * nDim);
-    // get holeIndices for earcut
-    const holeIndices: number[] = [];
-    while (primitivePolygonIndices[primitiveIndex] < endIdx) {
-      if (primitivePolygonIndices[primitiveIndex] > startIdx) {
-        holeIndices.push(primitivePolygonIndices[primitiveIndex] - startIdx);
+): Uint32Array | null {
+  try {
+    let primitiveIndex = 0;
+    const triangles: number[] = [];
+    // loop polygonIndices to get triangles
+    for (let i = 0; i < polygonIndices.length - 1; i++) {
+      const startIdx = polygonIndices[i];
+      const endIdx = polygonIndices[i + 1];
+      // get subarray of flatCoordinateArray
+      const slicedFlatCoords = flatCoordinateArray.subarray(startIdx * nDim, endIdx * nDim);
+      // get holeIndices for earcut
+      const holeIndices: number[] = [];
+      while (primitivePolygonIndices[primitiveIndex] < endIdx) {
+        if (primitivePolygonIndices[primitiveIndex] > startIdx) {
+          holeIndices.push(primitivePolygonIndices[primitiveIndex] - startIdx);
+        }
+        primitiveIndex++;
+      }
+      const triangleIndices = earcut(
+        slicedFlatCoords,
+        holeIndices.length > 0 ? holeIndices : undefined,
+        nDim
+      );
+      if (triangleIndices.length === 0) {
+        throw Error('can not tesselate invalid polygon');
+      }
+      for (let j = 0; j < triangleIndices.length; j++) {
+        triangles.push(triangleIndices[j] + startIdx);
       }
-      primitiveIndex++;
     }
-    const triangleIndices = earcut(
-      slicedFlatCoords,
-      holeIndices.length > 0 ? holeIndices : undefined,
-      nDim
-    );
-    for (let j = 0; j < triangleIndices.length; j++) {
-      triangles.push(triangleIndices[j] + startIdx);
+    // convert traingles to Uint32Array
+    const trianglesUint32 = new Uint32Array(triangles.length);
+    for (let i = 0; i < triangles.length; i++) {
+      trianglesUint32[i] = triangles[i];
     }
+    return trianglesUint32;
+  } catch (error) {
+    // TODO - add logging
+    // there is an expection when tesselating invalid polygon, e.g. polygon with self-intersection
+    // return null to skip tesselating
+    return null;
   }
-  // convert traingles to Uint32Array
-  const trianglesUint32 = new Uint32Array(triangles.length);
-  for (let i = 0; i < triangles.length; i++) {
-    trianglesUint32[i] = triangles[i];
-  }
-  return trianglesUint32;
 }
 
 /**
  * get binary polygons from geoarrow polygon column
  * @param chunk one chunk of geoarrow polygon column
  * @param geoEncoding the geo encoding of the geoarrow polygon column
+ * @param options options for getting binary geometries
  * @returns BinaryGeometryContent
  */
-function getBinaryPolygonsFromChunk(chunk: arrow.Data, geoEncoding: string): BinaryGeometryContent {
+function getBinaryPolygonsFromChunk(
+  chunk: arrow.Data,
+  geoEncoding: string,
+  options?: BinaryGeometriesFromArrowOptions
+): BinaryGeometryContent {
   const isMultiPolygon = geoEncoding === 'geoarrow.multipolygon';
 
   const polygonData = isMultiPolygon ? chunk.children[0] : chunk;
@@ -341,14 +373,17 @@ function getBinaryPolygonsFromChunk(chunk: arrow.Data, geoEncoding: string): Bin
     }
   }
 
-  const triangles = getTriangleIndices(geometryIndicies, geomOffset, flatCoordinateArray, nDim);
+  const triangles = options?.triangulate
+    ? getTriangleIndices(geometryIndicies, geomOffset, flatCoordinateArray, nDim)
+    : null;
+
   return {
     featureIds,
     flatCoordinateArray,
     nDim,
     geomOffset,
     geometryIndicies,
-    triangles
+    ...(options?.triangulate && triangles ? {triangles} : {})
   };
 }
 

modules/arrow/src/triangulate-on-worker.ts

@@ -22,7 +22,7 @@ export type TriangulateInput = {
 
 /** Result type for operation: 'triangulate' */
 export type TriangulateResult = TriangulateInput & {
-  triangleIndices: Uint32Array;
+  triangleIndices?: Uint32Array;
 };
 
 /**

modules/arrow/src/workers/triangulation-worker.ts

@@ -35,5 +35,5 @@ function triangulateBatch(data: TriangulateInput): TriangulateResult {
     data.flatCoordinateArray,
     data.nDim
   );
-  return {...data, triangleIndices};
+  return {...data, ...(triangleIndices ? {triangleIndices} : {})};
 }

modules/arrow/test/geoarrow/convert-geoarrow-to-binary-geometry.spec.ts

@@ -342,7 +342,7 @@ async function testGetBinaryGeometriesFromArrow(
 
     t.notEqual(encoding, undefined, 'encoding is not undefined');
     if (geoColumn && encoding) {
-      const options = {meanCenter: true};
+      const options = {calculateMeanCenters: true, triangulate: true};
       const binaryData = getBinaryGeometriesFromArrow(geoColumn, encoding, options);
       t.deepEqual(binaryData, expectedBinaryGeometries, 'binary geometries are correct');
     }