MeshLayer.getObjectPosition now samples up to ~100,000 vertices

Author: chrisj

src/mesh/frontend.ts

@@ -612,8 +612,8 @@ export class MeshLayer extends PerspectiveViewRenderLayer<ThreeDimensionalRender
       rank,
     );
     const { fragmentIds } = chunk;
-    const closestVertex = new Float32Array(rank);
-    let closestDistanceSq = Number.POSITIVE_INFINITY;
+    let vertexCount = 0;
+    const fragmentChunks: FragmentChunk[] = [];
     for (const fragmentId of fragmentIds) {
       const { key: fragmentKey } = this.source.getFragmentKey(key, fragmentId);
       const fragmentChunk = this.source.fragmentSource.chunks.get(fragmentKey);
@@ -625,9 +625,21 @@ export class MeshLayer extends PerspectiveViewRenderLayer<ThreeDimensionalRender
       ) {
         continue;
       }
+      vertexCount += meshData.vertexPositions.length / rank;
+      fragmentChunks.push(fragmentChunk);
+    }
+    // Only check up to ~100,000 vertices.
+    // Not exact because it restarts the interval for each fragment chunk.
+    const TARGET_VERTEX_COUNT = 100 * 1000;
+    const sampleRate = TARGET_VERTEX_COUNT / vertexCount;
+    const sampleInterval = Math.max(1, Math.floor(1 / sampleRate));
+    const closestVertex = new Float32Array(rank);
+    let closestDistanceSq = Number.POSITIVE_INFINITY;
+    for (const fragmentChunk of fragmentChunks) {
+      const { meshData } = fragmentChunk;
       const { vertexPositions } = meshData;
       if (vertexPositions.length < rank) continue;
-      for (let i = 0; i < vertexPositions.length; i += rank) {
+      for (let i = 0; i < vertexPositions.length; i += rank * sampleInterval) {
         let distanceSq = 0;
         for (let j = 0; j < rank; j++) {
           distanceSq +=