godot/core/math/triangle_mesh.cpp

/*************************************************************************/
/*  triangle_mesh.cpp                                                    */
/*************************************************************************/
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/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
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#include "triangle_mesh.h"
#include "sort.h"

int TriangleMesh::_create_bvh(BVH *p_bvh, BVH **p_bb, int p_from, int p_size, int p_depth, int &max_depth, int &max_alloc) {

	if (p_depth > max_depth) {
		max_depth = p_depth;
	}

	if (p_size == 1) {

		return p_bb[p_from] - p_bvh;
	} else if (p_size == 0) {

		return -1;
	}

	AABB aabb;
	aabb = p_bb[p_from]->aabb;
	for (int i = 1; i < p_size; i++) {

		aabb.merge_with(p_bb[p_from + i]->aabb);
	}

	int li = aabb.get_longest_axis_index();

	switch (li) {

		case Vector3::AXIS_X: {
			SortArray<BVH *, BVHCmpX> sort_x;
			sort_x.nth_element(0, p_size, p_size / 2, &p_bb[p_from]);
			//sort_x.sort(&p_bb[p_from],p_size);
		} break;
		case Vector3::AXIS_Y: {
			SortArray<BVH *, BVHCmpY> sort_y;
			sort_y.nth_element(0, p_size, p_size / 2, &p_bb[p_from]);
			//sort_y.sort(&p_bb[p_from],p_size);
		} break;
		case Vector3::AXIS_Z: {
			SortArray<BVH *, BVHCmpZ> sort_z;
			sort_z.nth_element(0, p_size, p_size / 2, &p_bb[p_from]);
			//sort_z.sort(&p_bb[p_from],p_size);

		} break;
	}

	int left = _create_bvh(p_bvh, p_bb, p_from, p_size / 2, p_depth + 1, max_depth, max_alloc);
	int right = _create_bvh(p_bvh, p_bb, p_from + p_size / 2, p_size - p_size / 2, p_depth + 1, max_depth, max_alloc);

	int index = max_alloc++;
	BVH *_new = &p_bvh[index];
	_new->aabb = aabb;
	_new->center = aabb.pos + aabb.size * 0.5;
	_new->face_index = -1;
	_new->left = left;
	_new->right = right;

	return index;
}

void TriangleMesh::create(const DVector<Vector3> &p_faces) {

	valid = false;

	int fc = p_faces.size();
	ERR_FAIL_COND(!fc || ((fc % 3) != 0));
	fc /= 3;
	triangles.resize(fc);

	bvh.resize(fc * 3); //will never be larger than this (todo make better)
	DVector<BVH>::Write bw = bvh.write();

	{

		//create faces and indices and base bvh
		//except for the Set for repeated triangles, everything
		//goes in-place.

		DVector<Vector3>::Read r = p_faces.read();
		DVector<Triangle>::Write w = triangles.write();
		Map<Vector3, int> db;

		for (int i = 0; i < fc; i++) {

			Triangle &f = w[i];
			const Vector3 *v = &r[i * 3];

			for (int j = 0; j < 3; j++) {

				int vidx = -1;
				Vector3 vs = v[j].snapped(0.0001);
				Map<Vector3, int>::Element *E = db.find(vs);
				if (E) {
					vidx = E->get();
				} else {
					vidx = db.size();
					db[vs] = vidx;
				}

				f.indices[j] = vidx;
				if (j == 0)
					bw[i].aabb.pos = vs;
				else
					bw[i].aabb.expand_to(vs);
			}

			f.normal = Face3(r[i * 3 + 0], r[i * 3 + 1], r[i * 3 + 2]).get_plane().get_normal();

			bw[i].left = -1;
			bw[i].right = -1;
			bw[i].face_index = i;
			bw[i].center = bw[i].aabb.pos + bw[i].aabb.size * 0.5;
		}

		vertices.resize(db.size());
		DVector<Vector3>::Write vw = vertices.write();
		for (Map<Vector3, int>::Element *E = db.front(); E; E = E->next()) {
			vw[E->get()] = E->key();
		}
	}

	DVector<BVH *> bwptrs;
	bwptrs.resize(fc);
	DVector<BVH *>::Write bwp = bwptrs.write();
	for (int i = 0; i < fc; i++) {

		bwp[i] = &bw[i];
	}

	max_depth = 0;
	int max_alloc = fc;
	int max = _create_bvh(bw.ptr(), bwp.ptr(), 0, fc, 1, max_depth, max_alloc);

	bw = DVector<BVH>::Write(); //clearup
	bvh.resize(max_alloc); //resize back

	valid = true;
}

Vector3 TriangleMesh::get_area_normal(const AABB &p_aabb) const {

	uint32_t *stack = (uint32_t *)alloca(sizeof(int) * max_depth);

	enum {
		TEST_AABB_BIT = 0,
		VISIT_LEFT_BIT = 1,
		VISIT_RIGHT_BIT = 2,
		VISIT_DONE_BIT = 3,
		VISITED_BIT_SHIFT = 29,
		NODE_IDX_MASK = (1 << VISITED_BIT_SHIFT) - 1,
		VISITED_BIT_MASK = ~NODE_IDX_MASK,

	};

	int n_count = 0;
	Vector3 n;

	int level = 0;

	DVector<Triangle>::Read trianglesr = triangles.read();
	DVector<Vector3>::Read verticesr = vertices.read();
	DVector<BVH>::Read bvhr = bvh.read();

	const Triangle *triangleptr = trianglesr.ptr();
	int pos = bvh.size() - 1;
	const BVH *bvhptr = bvhr.ptr();

	stack[0] = pos;
	while (true) {

		uint32_t node = stack[level] & NODE_IDX_MASK;
		const BVH &b = bvhptr[node];
		bool done = false;

		switch (stack[level] >> VISITED_BIT_SHIFT) {
			case TEST_AABB_BIT: {

				bool valid = b.aabb.intersects(p_aabb);
				if (!valid) {

					stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;

				} else {

					if (b.face_index >= 0) {

						const Triangle &s = triangleptr[b.face_index];
						n += s.normal;
						n_count++;

						stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;

					} else {

						stack[level] = (VISIT_LEFT_BIT << VISITED_BIT_SHIFT) | node;
					}
				}
				continue;
			}
			case VISIT_LEFT_BIT: {

				stack[level] = (VISIT_RIGHT_BIT << VISITED_BIT_SHIFT) | node;
				stack[level + 1] = b.left | TEST_AABB_BIT;
				level++;
				continue;
			}
			case VISIT_RIGHT_BIT: {

				stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;
				stack[level + 1] = b.right | TEST_AABB_BIT;
				level++;
				continue;
			}
			case VISIT_DONE_BIT: {

				if (level == 0) {
					done = true;
					break;
				} else
					level--;
				continue;
			}
		}

		if (done)
			break;
	}

	if (n_count > 0)
		n /= n_count;

	return n;
}

bool TriangleMesh::intersect_segment(const Vector3 &p_begin, const Vector3 &p_end, Vector3 &r_point, Vector3 &r_normal) const {

	uint32_t *stack = (uint32_t *)alloca(sizeof(int) * max_depth);

	enum {
		TEST_AABB_BIT = 0,
		VISIT_LEFT_BIT = 1,
		VISIT_RIGHT_BIT = 2,
		VISIT_DONE_BIT = 3,
		VISITED_BIT_SHIFT = 29,
		NODE_IDX_MASK = (1 << VISITED_BIT_SHIFT) - 1,
		VISITED_BIT_MASK = ~NODE_IDX_MASK,

	};

	Vector3 n = (p_end - p_begin).normalized();
	real_t d = 1e10;
	bool inters = false;

	int level = 0;

	DVector<Triangle>::Read trianglesr = triangles.read();
	DVector<Vector3>::Read verticesr = vertices.read();
	DVector<BVH>::Read bvhr = bvh.read();

	const Triangle *triangleptr = trianglesr.ptr();
	const Vector3 *vertexptr = verticesr.ptr();
	int pos = bvh.size() - 1;
	const BVH *bvhptr = bvhr.ptr();

	stack[0] = pos;
	while (true) {

		uint32_t node = stack[level] & NODE_IDX_MASK;
		const BVH &b = bvhptr[node];
		bool done = false;

		switch (stack[level] >> VISITED_BIT_SHIFT) {
			case TEST_AABB_BIT: {

				bool valid = b.aabb.intersects_segment(p_begin, p_end);
				//				bool valid = b.aabb.intersects(ray_aabb);

				if (!valid) {

					stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;

				} else {

					if (b.face_index >= 0) {

						const Triangle &s = triangleptr[b.face_index];
						Face3 f3(vertexptr[s.indices[0]], vertexptr[s.indices[1]], vertexptr[s.indices[2]]);

						Vector3 res;

						if (f3.intersects_segment(p_begin, p_end, &res)) {

							float nd = n.dot(res);
							if (nd < d) {

								d = nd;
								r_point = res;
								r_normal = f3.get_plane().get_normal();
								inters = true;
							}
						}

						stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;

					} else {

						stack[level] = (VISIT_LEFT_BIT << VISITED_BIT_SHIFT) | node;
					}
				}
				continue;
			}
			case VISIT_LEFT_BIT: {

				stack[level] = (VISIT_RIGHT_BIT << VISITED_BIT_SHIFT) | node;
				stack[level + 1] = b.left | TEST_AABB_BIT;
				level++;
				continue;
			}
			case VISIT_RIGHT_BIT: {

				stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;
				stack[level + 1] = b.right | TEST_AABB_BIT;
				level++;
				continue;
			}
			case VISIT_DONE_BIT: {

				if (level == 0) {
					done = true;
					break;
				} else
					level--;
				continue;
			}
		}

		if (done)
			break;
	}

	if (inters) {

		if (n.dot(r_normal) > 0)
			r_normal = -r_normal;
	}

	return inters;
}

bool TriangleMesh::intersect_ray(const Vector3 &p_begin, const Vector3 &p_dir, Vector3 &r_point, Vector3 &r_normal) const {

	uint32_t *stack = (uint32_t *)alloca(sizeof(int) * max_depth);

	enum {
		TEST_AABB_BIT = 0,
		VISIT_LEFT_BIT = 1,
		VISIT_RIGHT_BIT = 2,
		VISIT_DONE_BIT = 3,
		VISITED_BIT_SHIFT = 29,
		NODE_IDX_MASK = (1 << VISITED_BIT_SHIFT) - 1,
		VISITED_BIT_MASK = ~NODE_IDX_MASK,

	};

	Vector3 n = p_dir;
	real_t d = 1e20;
	bool inters = false;

	int level = 0;

	DVector<Triangle>::Read trianglesr = triangles.read();
	DVector<Vector3>::Read verticesr = vertices.read();
	DVector<BVH>::Read bvhr = bvh.read();

	const Triangle *triangleptr = trianglesr.ptr();
	const Vector3 *vertexptr = verticesr.ptr();
	int pos = bvh.size() - 1;
	const BVH *bvhptr = bvhr.ptr();

	stack[0] = pos;
	while (true) {

		uint32_t node = stack[level] & NODE_IDX_MASK;
		const BVH &b = bvhptr[node];
		bool done = false;

		switch (stack[level] >> VISITED_BIT_SHIFT) {
			case TEST_AABB_BIT: {

				bool valid = b.aabb.intersects_ray(p_begin, p_dir);
				if (!valid) {

					stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;

				} else {

					if (b.face_index >= 0) {

						const Triangle &s = triangleptr[b.face_index];
						Face3 f3(vertexptr[s.indices[0]], vertexptr[s.indices[1]], vertexptr[s.indices[2]]);

						Vector3 res;

						if (f3.intersects_ray(p_begin, p_dir, &res)) {

							float nd = n.dot(res);
							if (nd < d) {

								d = nd;
								r_point = res;
								r_normal = f3.get_plane().get_normal();
								inters = true;
							}
						}

						stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;

					} else {

						stack[level] = (VISIT_LEFT_BIT << VISITED_BIT_SHIFT) | node;
					}
				}
				continue;
			}
			case VISIT_LEFT_BIT: {

				stack[level] = (VISIT_RIGHT_BIT << VISITED_BIT_SHIFT) | node;
				stack[level + 1] = b.left | TEST_AABB_BIT;
				level++;
				continue;
			}
			case VISIT_RIGHT_BIT: {

				stack[level] = (VISIT_DONE_BIT << VISITED_BIT_SHIFT) | node;
				stack[level + 1] = b.right | TEST_AABB_BIT;
				level++;
				continue;
			}
			case VISIT_DONE_BIT: {

				if (level == 0) {
					done = true;
					break;
				} else
					level--;
				continue;
			}
		}

		if (done)
			break;
	}

	if (inters) {

		if (n.dot(r_normal) > 0)
			r_normal = -r_normal;
	}

	return inters;
}

bool TriangleMesh::is_valid() const {

	return valid;
}

DVector<Face3> TriangleMesh::get_faces() const {

	if (!valid)
		return DVector<Face3>();

	DVector<Face3> faces;
	int ts = triangles.size();
	faces.resize(triangles.size());

	DVector<Face3>::Write w = faces.write();
	DVector<Triangle>::Read r = triangles.read();
	DVector<Vector3>::Read rv = vertices.read();

	for (int i = 0; i < ts; i++) {
		for (int j = 0; j < 3; j++) {
			w[i].vertex[j] = rv[r[i].indices[j]];
		}
	}

	w = DVector<Face3>::Write();
	return faces;
}

TriangleMesh::TriangleMesh() {

	valid = false;
	max_depth = 0;
}