Fix infinite recursive loop in BVH building (#81)

When all primitive centroids are equal during a recursive BVH building step, it results in a recursive loop.
This fix detects this case and returns a leaf node instead.

Co-authored-by: Tom Janssens <tom@corebvba.be>

src/renderer/bvhAccel.js

@@ -149,6 +149,10 @@ function recursiveBuild(primitiveInfo, start, end) {
     }
     const dim = maximumExtent(centroidBounds);
 
+    if (centroidBounds.max[dim] === centroidBounds.min[dim]) {
+      return makeLeafNode(primitiveInfo.slice(start, end), bounds);
+    }
+
     let mid = Math.floor((start + end) / 2);
 
     // middle split method