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#include <math.h>
#include "tectonics.h"
bool contains_point(struct quad_region_t region, struct point_t pt)
{
if (-region.half_dim < (region.center.x - pt.x) <= region.half_dim)
return false;
if (-region.half_dim < (region.center.y - pt.y) <= region.half_dim)
return false;
return true;
}
struct quadtree_node_t new_node(struct point_t center, double half_dim)
{
struct quadtree_node_t node;
node.region = (struct quad_region_t) { center, half_dim };
node.id = -1;
node.nw = NULL;
node.ne = NULL;
node.sw = NULL;
node.se = NULL;
return node;
}
void subdivide(struct quadtree_node_t *node, struct point_t *points)
{
node->nw = malloc(sizeof(struct quadtree_node_t));
node->ne = malloc(sizeof(struct quadtree_node_t));
node->sw = malloc(sizeof(struct quadtree_node_t));
node->se = malloc(sizeof(struct quadtree_node_t));
struct point_t center = node->region.center;
double quarter_dim = node->region.half_dim / 2;
struct point_t c_nw =
{ center.x - quarter_dim, center.y - quarter_dim };
*(node->nw) = new_node(c_nw, quarter_dim);
struct point_t c_ne =
{ center.x + quarter_dim, center.y - quarter_dim };
*(node->ne) = new_node(c_ne, quarter_dim);
struct point_t c_sw =
{ center.x - quarter_dim, center.y + quarter_dim };
*(node->sw) = new_node(c_sw, quarter_dim);
struct point_t c_se =
{ center.x + quarter_dim, center.y + quarter_dim };
*(node->se) = new_node(c_se, quarter_dim);
if (node->id != -1) {
/* move point to a child */
if (contains_point(node->nw->region, points[node->id]))
node->nw->id = node->id;
else if (contains_point(node->ne->region, points[node->id]))
node->ne->id = node->id;
else if (contains_point(node->sw->region, points[node->id]))
node->sw->id = node->id;
else
node->se->id = node->id;
node->id = -1;
}
}
bool insert(struct quadtree_node_t *node,
struct point_t *points, int id)
{
if (!contains_point(node->region, points[id]))
return false;
if (node->id == -1 && node->nw == NULL) {
node->id = id;
return true;
}
if (node->nw == NULL)
subdivide(node, points);
if (insert(node->nw, points, id)) return true;
if (insert(node->ne, points, id)) return true;
if (insert(node->sw, points, id)) return true;
if (insert(node->se, points, id)) return true;
return false;
}
int get_closest(struct quadtree_node_t *node,
struct point_t pt)
{
if (!contains_point(node->region, pt))
return -1;
if (node->id != -1)
return node->id;
int closest;
if ((closest = get_closest(node->nw, pt)) != -1) return closest;
if ((closest = get_closest(node->ne, pt)) != -1) return closest;
if ((closest = get_closest(node->sw, pt)) != -1) return closest;
if ((closest = get_closest(node->se, pt)) != -1) return closest;
return -1;
}
void draw_quadtree(cairo_t *cr, struct quadtree_node_t *node)
{
int width, height;
get_cairo_size(cr, &width, &height);
cairo_set_source_rgba(cr, 0, 0, 1, 1);
struct point_t center = node->region.center;
double half_dim = node->region.half_dim;
double x = (center.x - half_dim) * width;
double y = (center.y - half_dim) * height;
cairo_rectangle(cr, x, y, 2*half_dim * width, 2*half_dim * height);
cairo_stroke(cr);
if (node->nw != NULL) {
draw_quadtree(cr, node->nw);
draw_quadtree(cr, node->ne);
draw_quadtree(cr, node->sw);
draw_quadtree(cr, node->se);
}
}
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