three-mesh-bvh
Version:
A BVH implementation to speed up raycasting against three.js meshes.
71 lines (46 loc) • 1.94 kB
JavaScript
/********************************************************/
/* This file is generated from "sortUtils.template.js". */
/********************************************************/
// reorders `tris` such that for `count` elements after `offset`, elements on the left side of the split
// will be on the left and elements on the right side of the split will be on the right. returns the index
// of the first element on the right side, or offset + count if there are no elements on the right side.
function partition( indirectBuffer, index, triangleBounds, offset, count, split ) {
let left = offset;
let right = offset + count - 1;
const pos = split.pos;
const axisOffset = split.axis * 2;
const boundsOffset = triangleBounds.offset || 0;
// hoare partitioning, see e.g. https://en.wikipedia.org/wiki/Quicksort#Hoare_partition_scheme
while ( true ) {
while ( left <= right && triangleBounds[ ( left - boundsOffset ) * 6 + axisOffset ] < pos ) {
left ++;
}
// if a triangle center lies on the partition plane it is considered to be on the right side
while ( left <= right && triangleBounds[ ( right - boundsOffset ) * 6 + axisOffset ] >= pos ) {
right --;
}
if ( left < right ) {
// we need to swap all of the information associated with the triangles at index
// left and right; that's the verts in the geometry index, the bounds,
// and perhaps the SAH planes
for ( let i = 0; i < 3; i ++ ) {
let t0 = index[ left * 3 + i ];
index[ left * 3 + i ] = index[ right * 3 + i ];
index[ right * 3 + i ] = t0;
}
// swap bounds
for ( let i = 0; i < 6; i ++ ) {
const l = left - boundsOffset;
const r = right - boundsOffset;
const tb = triangleBounds[ l * 6 + i ];
triangleBounds[ l * 6 + i ] = triangleBounds[ r * 6 + i ];
triangleBounds[ r * 6 + i ] = tb;
}
left ++;
right --;
} else {
return left;
}
}
}
export { partition };