From 5a56453390da1f74b3f1b9469fe84d6a31110724 Mon Sep 17 00:00:00 2001
From: Stewart Allen <stewart.allen@gmail.com>
Date: Sun, 8 Jan 2023 20:33:13 -0500
Subject: [PATCH] borrow bucket map from cam slicer to allow negative z indices

---
 src/add/three.js  |  8 ++++++++
 src/geo/slicer.js | 14 ++++++++------
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/add/three.js b/src/add/three.js
index e6e1bae5..b2db4c8c 100644
--- a/src/add/three.js
+++ b/src/add/three.js
@@ -22,6 +22,14 @@ THREE.computeFaceNormal = function(vA,vB,vC) {
     return cb;
 };
 
+// https://www.npmjs.com/package/three-mesh-bvh
+THREE.addBVH = function() {
+    const { computeBoundsTree, disposeBoundsTree, acceleratedRaycast } = MeshBVHLib;
+    THREE.BufferGeometry.prototype.computeBoundsTree = computeBoundsTree;
+    THREE.BufferGeometry.prototype.disposeBoundsTree = disposeBoundsTree;
+    THREE.Mesh.prototype.raycast = acceleratedRaycast;
+};
+
 THREE.dispose = function(obj) {
     if (!obj) {
         return;
diff --git a/src/geo/slicer.js b/src/geo/slicer.js
index ea020d2d..88bbaf9e 100644
--- a/src/geo/slicer.js
+++ b/src/geo/slicer.js
@@ -45,6 +45,7 @@ async function slice(points, options = {}) {
         zScale,                 // bucket span in z units
         zSum = 0.0,             // sanity check that points enclose non-zere volume
         buckets = [],           // banded/grouped faces to speed up slice/search
+        bucketMap = {},
         overlapMax = options.overlap || 0.75,
         bucketMax = options.bucketMax || 100,
         onupdate = options.onupdate || function() {},
@@ -161,11 +162,6 @@ async function slice(points, options = {}) {
         return {};
     }
 
-    // create empty buckets
-    for (i = 0; i < bucketCount; i++) {
-        buckets.push({ points: [], slices: [] });
-    }
-
     if (bucketCount > 1) {
         let failAt = (points.length * overlapMax) | 0, bucket;
         // copy triples into all matching z-buckets
@@ -179,7 +175,12 @@ async function slice(points, options = {}) {
                 bM = Math.min(Math.ceil(zM * zScale), bucketCount);
             // add point to all buckets in range
             for (j = bm; j < bM; j++) {
-                bucket = buckets[j].points;
+                let map = bucketMap[j];
+                if (!map) {
+                    map = bucketMap[j] = { points: [], slices: [] };
+                    buckets.push(map);
+                }
+                bucket = map.points;
                 bucket.push(p1);
                 bucket.push(p2);
                 bucket.push(p3);
@@ -196,6 +197,7 @@ async function slice(points, options = {}) {
     // fallback if we can't partition point space
     if (bucketCount === 1) {
         buckets = [{ points, slices: [] }];
+        bucketMap[0] = buckets[0];
     }
 
     // create buckets data structure