three-mesh-bvh/src/core/cast/shapecast.js

A BVH implementation to speed up raycasting against three.js meshes.

import { Box3 } from 'three';
import { CONTAINED, UINT32_PER_NODE } from '../Constants.js';
import { arrayToBox } from '../../utils/ArrayBoxUtilities.js';
import { PrimitivePool } from '../../utils/PrimitivePool.js';
import { COUNT, OFFSET, LEFT_NODE, RIGHT_NODE, IS_LEAF, BOUNDING_DATA_INDEX } from '../utils/nodeBufferUtils.js';
import { BufferStack } from '../utils/BufferStack.js';

let _box1, _box2;
const boxStack = [];
const boxPool = /* @__PURE__ */ new PrimitivePool( () => new Box3() );

export function shapecast( bvh, root, intersectsBounds, intersectsRange, boundsTraverseOrder, nodeOffset ) {

	// setup
	_box1 = boxPool.getPrimitive();
	_box2 = boxPool.getPrimitive();
	boxStack.push( _box1, _box2 );
	BufferStack.setBuffer( bvh._roots[ root ] );

	const result = shapecastTraverse( 0, bvh.geometry, intersectsBounds, intersectsRange, boundsTraverseOrder, nodeOffset );

	// cleanup
	BufferStack.clearBuffer();
	boxPool.releasePrimitive( _box1 );
	boxPool.releasePrimitive( _box2 );
	boxStack.pop();
	boxStack.pop();

	const length = boxStack.length;
	if ( length > 0 ) {

		_box2 = boxStack[ length - 1 ];
		_box1 = boxStack[ length - 2 ];

	}

	return result;

}

function shapecastTraverse(
	nodeIndex32,
	geometry,
	intersectsBoundsFunc,
	intersectsRangeFunc,
	nodeScoreFunc = null,
	nodeIndexOffset = 0, // offset for unique node identifier
	depth = 0
) {

	const { float32Array, uint16Array, uint32Array } = BufferStack;
	let nodeIndex16 = nodeIndex32 * 2;

	const isLeaf = IS_LEAF( nodeIndex16, uint16Array );
	if ( isLeaf ) {

		const offset = OFFSET( nodeIndex32, uint32Array );
		const count = COUNT( nodeIndex16, uint16Array );
		arrayToBox( BOUNDING_DATA_INDEX( nodeIndex32 ), float32Array, _box1 );
		return intersectsRangeFunc( offset, count, false, depth, nodeIndexOffset + nodeIndex32 / UINT32_PER_NODE, _box1 );

	} else {

		const left = LEFT_NODE( nodeIndex32 );
		const right = RIGHT_NODE( nodeIndex32, uint32Array );
		let c1 = left;
		let c2 = right;

		let score1, score2;
		let box1, box2;
		if ( nodeScoreFunc ) {

			box1 = _box1;
			box2 = _box2;

			// bounding data is not offset
			arrayToBox( BOUNDING_DATA_INDEX( c1 ), float32Array, box1 );
			arrayToBox( BOUNDING_DATA_INDEX( c2 ), float32Array, box2 );

			score1 = nodeScoreFunc( box1 );
			score2 = nodeScoreFunc( box2 );

			if ( score2 < score1 ) {

				c1 = right;
				c2 = left;

				const temp = score1;
				score1 = score2;
				score2 = temp;

				box1 = box2;
				// box2 is always set before use below

			}

		}

		// Check box 1 intersection
		if ( ! box1 ) {

			box1 = _box1;
			arrayToBox( BOUNDING_DATA_INDEX( c1 ), float32Array, box1 );

		}

		const isC1Leaf = IS_LEAF( c1 * 2, uint16Array );
		const c1Intersection = intersectsBoundsFunc( box1, isC1Leaf, score1, depth + 1, nodeIndexOffset + c1 / UINT32_PER_NODE );

		let c1StopTraversal;
		if ( c1Intersection === CONTAINED ) {

			const offset = getLeftOffset( c1 );
			const end = getRightEndOffset( c1 );
			const count = end - offset;

			c1StopTraversal = intersectsRangeFunc( offset, count, true, depth + 1, nodeIndexOffset + c1 / UINT32_PER_NODE, box1 );

		} else {

			c1StopTraversal =
				c1Intersection &&
				shapecastTraverse(
					c1,
					geometry,
					intersectsBoundsFunc,
					intersectsRangeFunc,
					nodeScoreFunc,
					nodeIndexOffset,
					depth + 1
				);

		}

		if ( c1StopTraversal ) return true;

		// Check box 2 intersection
		// cached box2 will have been overwritten by previous traversal
		box2 = _box2;
		arrayToBox( BOUNDING_DATA_INDEX( c2 ), float32Array, box2 );

		const isC2Leaf = IS_LEAF( c2 * 2, uint16Array );
		const c2Intersection = intersectsBoundsFunc( box2, isC2Leaf, score2, depth + 1, nodeIndexOffset + c2 / UINT32_PER_NODE );

		let c2StopTraversal;
		if ( c2Intersection === CONTAINED ) {

			const offset = getLeftOffset( c2 );
			const end = getRightEndOffset( c2 );
			const count = end - offset;

			c2StopTraversal = intersectsRangeFunc( offset, count, true, depth + 1, nodeIndexOffset + c2 / UINT32_PER_NODE, box2 );

		} else {

			c2StopTraversal =
				c2Intersection &&
				shapecastTraverse(
					c2,
					geometry,
					intersectsBoundsFunc,
					intersectsRangeFunc,
					nodeScoreFunc,
					nodeIndexOffset,
					depth + 1
				);

		}

		if ( c2StopTraversal ) return true;

		return false;

		// Define these inside the function so it has access to the local variables needed
		// when converting to the buffer equivalents
		function getLeftOffset( nodeIndex32 ) {

			const { uint16Array, uint32Array } = BufferStack;
			let nodeIndex16 = nodeIndex32 * 2;

			// traverse until we find a leaf
			while ( ! IS_LEAF( nodeIndex16, uint16Array ) ) {

				nodeIndex32 = LEFT_NODE( nodeIndex32 );
				nodeIndex16 = nodeIndex32 * 2;

			}

			return OFFSET( nodeIndex32, uint32Array );

		}

		function getRightEndOffset( nodeIndex32 ) {

			const { uint16Array, uint32Array } = BufferStack;
			let nodeIndex16 = nodeIndex32 * 2;

			// traverse until we find a leaf
			while ( ! IS_LEAF( nodeIndex16, uint16Array ) ) {

				// adjust offset to point to the right node
				nodeIndex32 = RIGHT_NODE( nodeIndex32, uint32Array );
				nodeIndex16 = nodeIndex32 * 2;

			}

			// return the end offset of the triangle range
			return OFFSET( nodeIndex32, uint32Array ) + COUNT( nodeIndex16, uint16Array );

		}

	}

}