godot/core/math/bsp_tree.cpp

/*************************************************************************/
/*  bsp_tree.cpp                                                         */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
/*                    http://www.godotengine.org                         */
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
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#include "bsp_tree.h"
#include "error_macros.h"
#include "print_string.h"


void BSP_Tree::from_aabb(const AABB& p_aabb) {

	planes.clear();

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

		Vector3 n;
		n[i]=1;
		planes.push_back(Plane(n,p_aabb.pos[i]+p_aabb.size[i]));
		planes.push_back(Plane(-n,-p_aabb.pos[i]));
	}

	nodes.clear();

	for(int i=0;i<6;i++) {

		Node n;
		n.plane=i;
		n.under=(i==0)?UNDER_LEAF:i-1;
		n.over=OVER_LEAF;
		nodes.push_back(n);
	}

	aabb=p_aabb;
	error_radius=0;
}

Vector<BSP_Tree::Node> BSP_Tree::get_nodes() const {

	return nodes;
}
Vector<Plane> BSP_Tree::get_planes() const {

	return planes;
}

AABB BSP_Tree::get_aabb() const {

	return aabb;
}

int BSP_Tree::_get_points_inside(int p_node,const Vector3* p_points,int *p_indices, const Vector3& p_center,const Vector3& p_half_extents,int p_indices_count) const {


	const Node *node =&nodes[p_node];
	const Plane &p = planes[node->plane];

	Vector3 min(
			(p.normal.x>0) ? -p_half_extents.x : p_half_extents.x,
			(p.normal.y>0) ? -p_half_extents.y : p_half_extents.y,
			(p.normal.z>0) ? -p_half_extents.z : p_half_extents.z
		);
	Vector3 max=-min;
	max+=p_center;
	min+=p_center;

	float dist_min = p.distance_to(min);
	float dist_max = p.distance_to(max);

	if ((dist_min * dist_max) < CMP_EPSILON ) { //intersection, test point by point


		int under_count=0;

		//sort points, so the are under first, over last
		for(int i=0;i<p_indices_count;i++) {

			int index=p_indices[i];

			if (p.is_point_over(p_points[index])) {

				// kind of slow (but cache friendly), should try something else,
				// but this is a corner case most of the time

				for(int j=index;j<p_indices_count-1;j++)
					p_indices[j]=p_indices[j+1];

				p_indices[p_indices_count-1]=index;

			} else {
				under_count++;
			}

		}

		int total=0;

		if (under_count>0) {
			if (node->under==UNDER_LEAF) {
				total+=under_count;
			} else {
				total+=_get_points_inside(node->under,p_points,p_indices,p_center,p_half_extents,under_count);
			}
		}

		if (under_count!=p_indices_count) {
			if (node->over==OVER_LEAF) {
				//total+=0 //if they are over an OVER_LEAF, they are outside the model
			} else {
				total+=_get_points_inside(node->over,p_points,&p_indices[under_count],p_center,p_half_extents,p_indices_count-under_count);
			}
		}

		return total;

	} else if (dist_min > 0 ) { //all points over plane

		if (node->over==OVER_LEAF) {

			return 0; // all these points are not visible
		}


		return _get_points_inside(node->over,p_points,p_indices,p_center,p_half_extents,p_indices_count);
	} else if (dist_min <= 0 ) { //all points behind plane

		if (node->under==UNDER_LEAF) {

			return p_indices_count; // all these points are visible
		}
		return _get_points_inside(node->under,p_points,p_indices,p_center,p_half_extents,p_indices_count);
	}

	return 0;
}

int BSP_Tree::get_points_inside(const Vector3* p_points,int p_point_count) const {


	if (nodes.size()==0)
		return 0;

#if 1
//this version is easier to debug, and and MUCH faster in real world cases

	int pass_count = 0;
	const Node *nodesptr=&nodes[0];
	const Plane *planesptr=&planes[0];
	int plane_count=planes.size();
	int node_count=nodes.size();

	if (node_count==0) // no nodes!
		return 0;

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

		const Vector3& point = p_points[i];
		if (!aabb.has_point(point)) {
			continue;
		}

		int idx=node_count-1;

		bool pass=false;

		while(true) {

			if (idx==OVER_LEAF) {
				pass=false;
				break;
			} else if (idx==UNDER_LEAF) {
				pass=true;
				break;
			}

			uint16_t plane=nodesptr[ idx ].plane;
#ifdef DEBUG_ENABLED

			ERR_FAIL_INDEX_V( plane, plane_count, false );
#endif

			idx = planesptr[ nodesptr[ idx ].plane ].is_point_over(point) ? nodes[ idx ].over : nodes[ idx ].under;

#ifdef DEBUG_ENABLED

			ERR_FAIL_COND_V( idx<MAX_NODES && idx>=node_count, false );
#endif

		}

		if (pass)
			pass_count++;
	}

	return pass_count;

#else
//this version scales better but it's slower for real world cases

	int *indices = (int*)alloca(p_point_count*sizeof(int));
	AABB bounds;

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

		indices[i]=i;
		if (i==0)
			bounds.pos=p_points[i];
		else
			bounds.expand_to(p_points[i]);

	}

	Vector3 half_extents = bounds.size/2.0;
	return _get_points_inside(nodes.size()+1,p_points,indices,bounds.pos+half_extents,half_extents,p_point_count);
#endif
}



bool BSP_Tree::point_is_inside(const Vector3& p_point) const {

	if (!aabb.has_point(p_point)) {
		return false;
	}

	int node_count=nodes.size();

	if (node_count==0) // no nodes!
		return false;


	const Node *nodesptr=&nodes[0];
	const Plane *planesptr=&planes[0];
	int plane_count=planes.size();

	int idx=node_count-1;
	int steps=0;

	while(true) {

		if (idx==OVER_LEAF) {
			return false;
		}
		if (idx==UNDER_LEAF) {

			return true;
		}

		uint16_t plane=nodesptr[ idx ].plane;
#ifdef DEBUG_ENABLED

		ERR_FAIL_INDEX_V( plane, plane_count, false );
#endif
		bool over = planesptr[ nodesptr[ idx ].plane ].is_point_over(p_point);

		idx =  over ? nodes[ idx ].over : nodes[ idx ].under;

#ifdef DEBUG_ENABLED

		ERR_FAIL_COND_V( idx<MAX_NODES && idx>=node_count, false );
#endif

		steps++;
	}

	return false;
}


static int _bsp_find_best_half_plane(const Face3* p_faces,const Vector<int>& p_indices,float p_tolerance) {

	int ic = p_indices.size();
	const int*indices=p_indices.ptr();

	int best_plane = -1;
	float best_plane_cost = 1e20;

	// Loop to find the polygon that best divides the set.

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

		const Face3& f=p_faces[ indices[i] ];
		Plane p = f.get_plane();

		int num_over=0,num_under=0,num_spanning=0;

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

			if (i==j)
				continue;

			const Face3& g=p_faces[ indices[j] ];
			int over=0,under=0;

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

				float d = p.distance_to(g.vertex[j]);

				if (Math::abs(d)>p_tolerance) {

					if (d > 0)
						over++;
					else
						under++;
				}

			}

			if (over && under)
				num_spanning++;
			else if (over)
				num_over++;
			else
				num_under++;

		}



		//double split_cost = num_spanning / (double) face_count;
		double relation = Math::abs(num_over-num_under) / (double) ic;

		// being honest, i never found a way to add split cost to the mix in a meaninguful way
		// in this engine, also, will likely be ignored anyway

		double plane_cost = /*split_cost +*/ relation;

		//printf("plane %i, %i over, %i under, %i spanning, cost is %g\n",i,num_over,num_under,num_spanning,plane_cost);
		if (plane_cost<best_plane_cost) {

			best_plane=i;
			best_plane_cost=plane_cost;
		}

	}

	return best_plane;

}


static int _bsp_create_node(const Face3 *p_faces,const Vector<int>& p_indices,Vector<Plane> &p_planes, Vector<BSP_Tree::Node> &p_nodes,float p_tolerance) {

	ERR_FAIL_COND_V( p_nodes.size() == BSP_Tree::MAX_NODES, -1 );

	// should not reach here
	ERR_FAIL_COND_V( p_indices.size() == 0, -1 )

	int ic = p_indices.size();
	const int*indices=p_indices.ptr();

	int divisor_idx = _bsp_find_best_half_plane(p_faces,p_indices,p_tolerance);

	// returned error
	ERR_FAIL_COND_V( divisor_idx<0 , -1 );


	Vector<int> faces_over;
	Vector<int> faces_under;

	Plane divisor_plane=p_faces[ indices[divisor_idx] ].get_plane();

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

		if (i==divisor_idx)
			continue;

		const Face3& f=p_faces[ indices[i] ];

		//if (f.get_plane().is_almost_like(divisor_plane))
		//	continue;

		int over_count=0;
		int under_count=0;

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

			float d = divisor_plane.distance_to(f.vertex[j]);
			if (Math::abs(d)>p_tolerance) {

				if (d > 0)
					over_count++;
				else
					under_count++;
			}
		}

		if (over_count)
			faces_over.push_back( indices[i] );
		if (under_count)
			faces_under.push_back( indices[i] );

	}



	uint16_t over_idx=BSP_Tree::OVER_LEAF,under_idx=BSP_Tree::UNDER_LEAF;

	if (faces_over.size()>0) { //have facess above?

		int idx = _bsp_create_node( p_faces, faces_over, p_planes, p_nodes,p_tolerance );
		if (idx>=0)
			over_idx=idx;
	}

	if (faces_under.size()>0) { //have facess above?

		int idx = _bsp_create_node( p_faces,faces_under, p_planes, p_nodes,p_tolerance );
		if (idx>=0)
			under_idx=idx;
	}

	/* Create the node */

	// find existing divisor plane
	int divisor_plane_idx=-1;


	for (int i=0;i<p_planes.size();i++) {

		if (p_planes[i].is_almost_like( divisor_plane )) {
			divisor_plane_idx=i;
			break;
		}
	}

	if (divisor_plane_idx==-1) {

		ERR_FAIL_COND_V( p_planes.size() == BSP_Tree::MAX_PLANES, -1 );
		divisor_plane_idx=p_planes.size();
		p_planes.push_back( divisor_plane );
	}

	BSP_Tree::Node node;
	node.plane=divisor_plane_idx;
	node.under=under_idx;
	node.over=over_idx;

	p_nodes.push_back(node);

	return p_nodes.size()-1;
}


BSP_Tree::operator Variant() const {


	Dictionary d;
	d["error_radius"]=error_radius;

	Vector<float> plane_values;
	plane_values.resize(planes.size()*4);

	for(int i=0;i<planes.size();i++) {

		plane_values[i*4+0]=planes[i].normal.x;
		plane_values[i*4+1]=planes[i].normal.y;
		plane_values[i*4+2]=planes[i].normal.z;
		plane_values[i*4+3]=planes[i].d;
	}

	d["planes"]=plane_values;

	DVector<int> dst_nodes;
	dst_nodes.resize(nodes.size()*3);

	for(int i=0;i<nodes.size();i++) {

		dst_nodes.set(i*3+0,nodes[i].over);
		dst_nodes.set(i*3+1,nodes[i].under);
		dst_nodes.set(i*3+2,nodes[i].plane);
	}


	d["nodes"]=dst_nodes;
	d["aabb"] = aabb;

	return Variant(d);
}

BSP_Tree::BSP_Tree() {

}


BSP_Tree::BSP_Tree(const Variant& p_variant) {

	Dictionary d=p_variant;
	ERR_FAIL_COND(!d.has("nodes"));
	ERR_FAIL_COND(!d.has("planes"));
	ERR_FAIL_COND(!d.has("aabb"));
	ERR_FAIL_COND(!d.has("error_radius"));

	DVector<int> src_nodes = d["nodes"];
	ERR_FAIL_COND(src_nodes.size()%3);


	if (d["planes"].get_type()==Variant::REAL_ARRAY) {

		DVector<float> src_planes=d["planes"];
		int plane_count=src_planes.size();
		ERR_FAIL_COND(plane_count%4);
		planes.resize(plane_count/4);

		if (plane_count) {
			DVector<float>::Read r = src_planes.read();
			for(int i=0;i<plane_count/4;i++) {

				planes[i].normal.x=r[i*4+0];
				planes[i].normal.y=r[i*4+1];
				planes[i].normal.z=r[i*4+2];
				planes[i].d=r[i*4+3];
			}
		}


	} else {

		planes = d["planes"];
	}


	error_radius = d["error"];
	aabb = d["aabb"];

//	int node_count = src_nodes.size();
	nodes.resize(src_nodes.size()/3);

	DVector<int>::Read r = src_nodes.read();

	for(int i=0;i<nodes.size();i++) {

		nodes[i].over=r[i*3+0];
		nodes[i].under=r[i*3+1];
		nodes[i].plane=r[i*3+2];
	}

}

BSP_Tree::BSP_Tree(const DVector<Face3>& p_faces,float p_error_radius) {

	// compute aabb

	int face_count=p_faces.size();
	DVector<Face3>::Read faces_r=p_faces.read();
	const Face3 *facesptr = faces_r.ptr();


	bool first=true;

	Vector<int> indices;

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

		const Face3& f=facesptr[i];

		if (f.is_degenerate())
			continue;

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

			if (first) {

				aabb.pos=f.vertex[0];
				first=false;
			} else {

				aabb.expand_to(f.vertex[j]);
			}
		}

		indices.push_back(i);

	}

	ERR_FAIL_COND( aabb.has_no_area() );

	int top = _bsp_create_node(faces_r.ptr(),indices,planes,nodes,aabb.get_longest_axis_size()*0.0001);

	if (top<0) {

		nodes.clear();
		planes.clear();
		ERR_FAIL_COND( top < 0 );
	}




	error_radius=p_error_radius;
}

BSP_Tree::BSP_Tree(const Vector<Node> &p_nodes, const Vector<Plane> &p_planes, const AABB& p_aabb,float p_error_radius) {

	nodes=p_nodes;
	planes=p_planes;
	aabb=p_aabb;
	error_radius=p_error_radius;

}

BSP_Tree::~BSP_Tree() {


}