path: root/quadtree.cpp

#include "quadtree.h"
#include "vector.h"

#include "gl.h"

#include <cmath>
#include <queue>

using std::min;
using std::max;

Quadtree::QuadNode::QuadNode(QuadChunk *chunk, float x, float y, float width, float height) {
	this->chunk = chunk;
	this->x = x;
	this->y = y;
	this->width = width;
	this->height = height;

	fill();
}

Quadtree::QuadNode::~QuadNode() {
}

float Quadtree::QuadNode::distance(float px, float pz) {
	bool in_width = px > x && px < x+width;
	bool in_height = pz > y && pz < y+height;

	if(in_width && in_height)
		return 0;

	Vector2 p(px, pz);

	float a = (p - Vector2(x, y)).length();
	float b = (p - Vector2(x+width, y)).length();
	float c = (p - Vector2(x, y+height)).length();
	float d = (p - Vector2(x+width, y+height)).length();

	float dist = min(min(min(a, b), c), d);

	if(in_width)
		dist = min(dist, (float)min(abs(y - pz), abs(y+height - pz)));
	if(in_height)
		dist = min(dist, (float)min(abs(x - px), abs(x+width - px)));

	return dist;
}

void Quadtree::QuadNode::fill() {
	vertex_array[0] = x + width / 2;
	vertex_array[1] = chunk->tree->heights[(int)floorf((int)(x + width/2)*chunk->tree->height + (int)(y + height/2))];
	vertex_array[2] = y + height / 2;

	vertex_array[3] = x;
	vertex_array[4] = chunk->tree->heights[(int)floorf(x*chunk->tree->height+y)];
	vertex_array[5] = y;

	vertex_array[6] = x;
	vertex_array[7] = chunk->tree->heights[(int)floorf(x*chunk->tree->height + (y + height))];
	vertex_array[8] = y + height;

	vertex_array[9] = x + width;
	vertex_array[10] = chunk->tree->heights[(int)floorf((x + width)*chunk->tree->height + (y + height))];
	vertex_array[11] = y + height;

	vertex_array[12] = x + width;
	vertex_array[13] = chunk->tree->heights[(int)floorf((x + width)*chunk->tree->height + y)];
	vertex_array[14] = y;

	/* midpoint is average of corner heights when width == 1 */
	if(width == 1) {
		vertex_array[1] = (vertex_array[4] + vertex_array[7] + vertex_array[10] + vertex_array[13])/4;
	}
}

void Quadtree::QuadNode::draw() {
	float tex_coords[4][3][2] = {
		{{.5, .5}, {0, 0}, {0, 1}},
		{{.5, .5}, {0, 1}, {1, 1}},
		{{.5, .5}, {1, 1}, {1, 0}},
		{{.5, .5}, {1, 0}, {0, 0}}
	};

	glBegin(GL_TRIANGLES);
	for(int i = 0; i < 4; i++) {
		Vector3 a(vertex_array[0], vertex_array[1], vertex_array[2]);
		Vector3 b(vertex_array[i*3+3], vertex_array[i*3+4], vertex_array[i*3+5]);
		Vector3 c(vertex_array[i == 3 ? 3 : (i*3+6)], vertex_array[i == 3 ? 4 : (i*3+7)], vertex_array[i == 3 ? 5 : (i*3+8)]);

		Vector3 U(c.x-a.x, c.y-a.y, c.z-a.z);
		Vector3 V(b.x-a.x, b.y-a.y, b.z-a.z);
		Vector3 N(V.cross(U));
		glNormal3f(N.x, N.y, N.z);

		glTexCoord2f(tex_coords[i][0][0], tex_coords[i][0][1]);
		glVertex3f(a.x, a.y, a.z);

		glTexCoord2f(tex_coords[i][1][0], tex_coords[i][1][1]);
		glVertex3f(b.x, b.y, b.z);

		glTexCoord2f(tex_coords[i][2][0], tex_coords[i][2][1]);
		glVertex3f(c.x, c.y, c.z);
	}
	glEnd();
}

void Quadtree::QuadNode::draw_grid() {
	glNormal3f(0, 1, 0);
	glBegin(GL_LINES);
	for(int i = 0; i < 4; i++) {
		Vector3 a(vertex_array[0], vertex_array[1], vertex_array[2]);
		Vector3 b(vertex_array[i*3+3], vertex_array[i*3+4], vertex_array[i*3+5]);

		glVertex3f(a.x, a.y, a.z);
		glVertex3f(b.x, b.y, b.z);
	}
	glEnd();
	glBegin(GL_LINE_LOOP);
		glVertex3f(vertex_array[3], vertex_array[4], vertex_array[5]);
		glVertex3f(vertex_array[6], vertex_array[7], vertex_array[8]);
		glVertex3f(vertex_array[9], vertex_array[10], vertex_array[11]);
		glVertex3f(vertex_array[12], vertex_array[13], vertex_array[14]);
	glEnd();
}

float Quadtree::QuadNode::get_height(float px, float py) {
	bool left;
	bool top;
	top = px - x >= height - (py - y);
	left = px - x >= py - y;
	Vector3 a(vertex_array[0], vertex_array[1], vertex_array[2]);
	Vector3 b, c;
	int bi, ci;
	if(left) {
		if(top) {
			bi = 3*3;
			ci = 4*3;
		} else {
			bi = 4*3;
			ci = 1*3;
		}
	} else {
		if(top) {
			bi = 2*3;
			ci = 3*3;
		} else {
			bi = 1*3;
			ci = 2*3;
		}
	}
	b = Vector3(vertex_array[bi], vertex_array[bi+1], vertex_array[bi+2]);
	c = Vector3(vertex_array[ci], vertex_array[ci+1], vertex_array[ci+2]);
	float det1 = (b.z - c.z) * (a.x - c.x) + (c.x - b.x) * (a.z - c.z);
	float det2 = (c.z - a.z) * (b.x - c.x) + (a.x - c.x) * (b.z - c.z);
	float l1 = ((b.z - c.z) * (px - c.x) + (c.x - b.x) * (py - c.z)) / det1;
	float l2 = ((c.z - a.z) * (px - c.x) + (a.x - c.x) * (py - c.z)) / det2;
	float l3 = 1 - l1 - l2;
	return l1 * a.y + l2 * b.y + l3 * c.y;
}

/* QuadChunk */

Quadtree::QuadChunk::QuadChunk(Quadtree *tree, float x, float y, float width, float height) {
	this->tree = tree;
	this->x = x;
	this->y = y;
	this->width = width;
	this->height = height;
	this->vbo_object = this->node_count = this->vertices = 0;
	this->nodes = NULL;

	if(width / chunk_size > 1) {
		for(int i = 0; i < 4; i++) {
			float nx = x + ((i & 1) ^((i & 2) >> 1)) * width / 2;
			float ny = y + ((i & 2) >> 1) * height / 2;
			children[i] = new QuadChunk(tree, nx, ny, width / 2, height / 2);
		}
		return;
	}

	node_count = width*height;
	nodes = new QuadNode*[node_count];
	for(int i = 0; i < height; i++) {
		for(int j = 0; j < width; j++) {
			nodes[j*(int)height + i] = new QuadNode(this, x+j, y+i, 1, 1);
		}
	}
}

Quadtree::QuadChunk::~QuadChunk() {
	for(unsigned int i = 0; i < node_count; i++)
		delete nodes[i];
	delete[] nodes;
}

float Quadtree::QuadChunk::distance(float px, float pz) {
	bool in_width = px > x && px < x+width;
	bool in_height = pz > y && pz < y+height;

	if(in_width && in_height)
		return 0;

	Vector2 p(px, pz);

	float a = (p - Vector2(x, y)).length();
	float b = (p - Vector2(x+width, y)).length();
	float c = (p - Vector2(x, y+height)).length();
	float d = (p - Vector2(x+width, y+height)).length();

	float dist = min(min(min(a, b), c), d);

	if(in_width)
		dist = min(dist, (float)min(abs(y - pz), abs(y+height - pz)));
	if(in_height)
		dist = min(dist, (float)min(abs(x - px), abs(x+width - px)));

	return dist;
}

void Quadtree::QuadChunk::make_vbo() {
	node_count = width*height;
	vertices = node_count*12;
	glGenBuffers(1, &vbo_object);
	glBindBuffer(GL_ARRAY_BUFFER, vbo_object);

	const size_t vertex_chunk_size = /*sizeof(float)*/3*12;
	const size_t vertices_size = vertex_chunk_size*node_count;
	const size_t normal_chunk_size = vertex_chunk_size;
	const size_t normals_size = normal_chunk_size*node_count;
	const size_t tex_coord_chunk_size = /*sizeof(float)*/2*12;
	const size_t tex_coords_size = tex_coord_chunk_size*node_count;

	buf_size = sizeof(float)*(vertices_size + normals_size + tex_coords_size);

	glBufferData(GL_ARRAY_BUFFER, buf_size, NULL, GL_STATIC_DRAW);

	float *buffer = (float*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);

	for(unsigned int index = 0; index < node_count; index++) {
		Quadtree::QuadNode *node = nodes[index];
		float tex_coords[4][3][2] = {
			{{.5, .5}, {0, 0}, {0, 1}},
			{{.5, .5}, {0, 1}, {1, 1}},
			{{.5, .5}, {1, 1}, {1, 0}},
			{{.5, .5}, {1, 0}, {0, 0}}
		};
		for(int i = 0; i < 4; i++) {
			float *v = buffer + vertex_chunk_size*index + 3*3*i;
			for(int j = 0; j < 3; j++) {
				float *tc = buffer + vertices_size + normals_size + tex_coord_chunk_size*index + 6*i + 2*j;
				tc[0] = tex_coords[i][j][0]*node->width;
				tc[1] = tex_coords[i][j][1]*node->height;
			}

			v[0] = node->vertex_array[0];
			v[1] = node->vertex_array[1];
			v[2] = node->vertex_array[2];

			v[3] = node->vertex_array[i*3+3];
			v[4] = node->vertex_array[i*3+4];
			v[5] = node->vertex_array[i*3+5];

			v[6] = node->vertex_array[i == 3 ? 3 : (i*3+6)];
			v[7] = node->vertex_array[i == 3 ? 4 : (i*3+7)];
			v[8] = node->vertex_array[i == 3 ? 5 : (i*3+8)];
		}

		float *n = buffer + vertices_size + normal_chunk_size*index;

		Vector3 bl = tree->normals[(int)((node->x+1)*tree->height + node->y)];
		Vector3 br = tree->normals[(int)(node->x*tree->height + node->y)];
		Vector3 tr = tree->normals[(int)(node->x*tree->height + node->y+1)];
		Vector3 tl = tree->normals[(int)((node->x+1)*tree->height + node->y+1)];

		n[24] = n[30] = bl.x;
		n[25] = n[31] = bl.y;
		n[26] = n[32] = bl.z;

		n[3] = n[33] = br.x;
		n[4] = n[34] = br.y;
		n[5] = n[35] = br.z;

		n[6] = n[12] = tr.x;
		n[7] = n[13] = tr.y;
		n[8] = n[14] = tr.z;

		n[15] = n[21] = tl.x;
		n[16] = n[22] = tl.y;
		n[17] = n[23] = tl.z;

		if(node->width == 1) {
			Vector3 v(bl + br + tr + tl);
			v /= v.length();
			n[0] = n[9] = n[18] = n[27] = v.x;
			n[1] = n[10] = n[19] = n[28] = v.y;
			n[2] = n[11] = n[20] = n[29] = v.z;
		} else {
			Vector3 v(tree->normals[(int)((node->x+node->width/2)*tree->height + node->y+node->height/2)]);
			n[0] = n[9] = n[18] = n[27] = v.x;
			n[1] = n[10] = n[19] = n[28] = v.y;
			n[2] = n[11] = n[20] = n[29] = v.z;
		}
	}

	glUnmapBuffer(GL_ARRAY_BUFFER);
}

Quadtree::QuadNode* Quadtree::QuadChunk::find(float x, float y) {
	if(!nodes) {
		float mx = this->x + width / 2;
		float my = this->y + height / 2;
		int i = 2*(y > my);
		if(i < 2 && x > mx)
			i = 1;
		else if(i == 2 && x < mx)
			i = 3;
		return children[i]->find(x, y);
	}
	if(!(x >= this->x && x < this->x+width && y >= this->y && y < this->y+height))
		return NULL;
	return nodes[(int)(x-this->x)*(int)height + (int)(y - this->y)];
}

/* Quadtree */

Quadtree::Quadtree(int width, int height, float *heightmap) {
	this->width = width;
	this->height = height;
	heights = heightmap;

	root = new QuadChunk(this, 0, 0, width-1, height-1);

	normals = new Vector3[width*height];
	for(int x = 0; x < width; x++) {
		for(int y = 0; y < height; y++) {
			Vector3 p(x, heights[x*height + y], y);
			Vector3 N;

			if(x > 0) {
				Vector3 U = Vector3(x-1, heights[(x-1)*height + y], y) - p;
				if(y > 0) {
					Vector3 V = Vector3(x, heights[x*height + y - 1], y-1) - p;
					N += V.cross(U);
				}
				if(y < height-1) {
					Vector3 V = Vector3(x, heights[x*height + y + 1], y+1) - p;
					N += U.cross(V);
				}
			}
			if(x < width-1) {
				Vector3 U = Vector3(x+1, heights[(x+1)*height + y], y) - p;
				if(y > 0) {
					Vector3 V = Vector3(x, heights[x*height + y - 1], y-1) - p;
					N += U.cross(V);
				}
				if(y < height-1) {
					Vector3 V = Vector3(x, heights[x*height + y + 1], y+1) - p;
					N += V.cross(U);
				}
			}
			normals[x*height + y] = N / N.length();
		}
	}
}

Quadtree::~Quadtree() {
	delete root;
	delete[] heights;
	delete[] normals;
}

void Quadtree::update(float x, float z) {
	std::queue<QuadChunk*> q;
	q.push(root);
	while(!q.empty()) {
		QuadChunk *chunk = q.front();
		q.pop();
		if(!chunk->nodes) {
			for(int i = 0; i < 4; i++)
				q.push(chunk->children[i]);
			continue;
		}

		float d = chunk->distance(x, z);
		if(d < 100 && !chunk->vbo_object) {
			chunk->make_vbo();
		} else if(d > 100 && chunk->vbo_object) {
			glDeleteBuffers(1, &chunk->vbo_object);
			chunk->vbo_object = 0;
			chunk->vertices = 0;
		}
	}
}

Quadtree::QuadNode *Quadtree::find(float x, float y) {
	return root->find(x, y);
}

Quadtree::QuadNode *Quadtree::get_left(Quadtree::QuadNode *node) {
	QuadNode *n = find(node->x + node->width*1.5, node->y + node->height / 2);
	if(n == node)
		return NULL;
	return n;
}

Quadtree::QuadNode *Quadtree::get_right(Quadtree::QuadNode *node) {
	QuadNode *n = find(node->x - node->width/2, node->y + node->height / 2);
	if(n == node)
		return NULL;
	return n;
}

Quadtree::QuadNode *Quadtree::get_up(Quadtree::QuadNode *node) {
	QuadNode *n = find(node->x + node->width/2, node->y + node->height*1.5);
	if(n == node)
		return NULL;
	return n;
}

Quadtree::QuadNode *Quadtree::get_down(Quadtree::QuadNode *node) {
	QuadNode *n = find(node->x + node->width/2, node->y);
	if(n == node)
		return NULL;
	return n;
}