Implement intersection algorithm

This commit is contained in:
Markus Koch 2020-05-01 20:48:36 +02:00
parent ce4295f674
commit f9e9726974
3 changed files with 380 additions and 1 deletions

291
src/dijkstrasearch.c Normal file
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#include "dijkstrasearch.h"
#include <stdlib.h>
#include <glib/glist.h>
#include <math.h>
#define FP_THRESHOLD 0.01
int dijkstra_node_same (struct dijkstra_node *node_a,
struct dijkstra_node *node_b)
{
int same = 1;
// Not the proper way to do it, but it works for now.
same &= (fabs(node_a->position.x - node_b->position.x) < FP_THRESHOLD);
same &= (fabs(node_a->position.y - node_b->position.y) < FP_THRESHOLD);
return same;
}
struct dijkstra_node *dijkstra_node_exists(GList *list,
struct dijkstra_node *node)
{
GList *l;
struct dijkstra_node *node_existing;
for (l = list; l != NULL; l = l->next) {
node_existing = (struct dijkstra_node*) l->data;
if (dijkstra_node_same(node, node_existing)) {
return node_existing;
}
}
return NULL;
}
/*!
* \brief dijkstra_node_new_to_list creates a new node entry if it does not already exist in the list
* \param list list of dijkstra_node
* \param x
* \param y
* \param is_new When != NULL: is_new will be set to true if a new node had to be created
* \return a dijkstra_node with the specified position (either newly created or from the list). Or NULL on error.
*/
struct dijkstra_node *dijkstra_node_new_to_list(GList **list,
float x,
float y,
int *is_new)
{
struct dijkstra_node *node;
struct dijkstra_node *found;
node = dijkstra_node_new(x, y);
if (!node)
return NULL;
if ((found = dijkstra_node_exists(*list, node))) {
free(node);
node = found;
if (is_new)
*is_new = 0;
} else {
*list = g_list_append(*list, node);
if (is_new)
*is_new = 1;
}
return node;
}
int dijkstra_connect_destination_node_to_path(struct dijkstra_node *destination,
struct dijkstra_path *path)
{
if (!path || !destination)
return -1;
destination->paths = g_list_append(destination->paths, (gpointer) path);
path->destination = destination;
return 0;
}
int dijkstra_connect_source_node_to_path(struct dijkstra_node *source,
struct dijkstra_path *path)
{
if (!path || !source)
return -1;
source->paths = g_list_append(source->paths, (gpointer) path);
path->source = source;
return 0;
}
/*!
* \brief dijkstra_connect_nodes_to_path connect the two nodes using the path
* \param source
* \param destination
* \param path
* \return
*/
int dijkstra_connect_nodes_to_path(struct dijkstra_node *source,
struct dijkstra_node *destination,
struct dijkstra_path *path)
{
int ret = 0;
ret |= dijkstra_connect_source_node_to_path(source, path);
ret |= dijkstra_connect_destination_node_to_path(destination, path);
return ret;
}
// WARNING: This does not update the references in the nodes!!!
struct dijkstra_path *dijkstra_path_dup_shallow(struct dijkstra_path *path)
{
struct dijkstra_path *dup;
if (!path)
return NULL;
dup = malloc(sizeof(*path));
if (dup) {
memcpy(dup, path, sizeof(*path));
}
return dup;
}
struct dijkstra_node *dijkstra_disconnect_node_from_path(struct dijkstra_path *path,
struct dijkstra_node *node,
int ref_only)
{
node->paths = g_list_remove(node->paths, (gpointer) node);
if (ref_only)
return node;
if (path->source == node)
path->source = NULL;
if (path->destination == node)
path->destination = NULL;
return node;
}
int dijkstra_path_intersect(GList **nodes,
GList **paths,
struct dijkstra_path *path_a,
struct dijkstra_path *path_b)
{
// Yes, I was too lazy to code this myself:
// https://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect
struct dijkstra_path *path_new;
struct dijkstra_node *node_new;
float p0_x, p0_y, p1_x, p1_y;
float p2_x, p2_y, p3_x, p3_y;
float i_x, i_y;
float s1_x, s1_y, s2_x, s2_y;
float s, t;
int is_new;
if (!path_a || !path_b)
return -1;
p0_x = path_a->source->position.x;
p0_y = path_a->source->position.y;
p1_x = path_a->destination->position.x;
p1_y = path_a->destination->position.y;
p2_x = path_b->source->position.x;
p2_y = path_b->source->position.y;
p3_x = path_b->destination->position.x;
p3_y = path_b->destination->position.y;
s1_x = p1_x - p0_x;
s1_y = p1_y - p0_y;
s2_x = p3_x - p2_x;
s2_y = p3_y - p2_y;
s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1)
{
// Collision detected
i_x = p0_x + (t * s1_x);
i_y = p0_y + (t * s1_y);
node_new = dijkstra_node_new_to_list(nodes, i_x, i_y, &is_new);
if (node_new != path_a->source && node_new != path_a->destination) {
path_new = dijkstra_path_dup_shallow(path_a);
*paths = g_list_append(*paths, (gpointer) path_new);
dijkstra_disconnect_node_from_path(path_a, path_a->destination, 1);
dijkstra_connect_destination_node_to_path(node_new, path_a);
dijkstra_connect_source_node_to_path(node_new, path_new);
}
// Now do the same thing for path b
if (node_new != path_b->source && node_new != path_b->destination) {
path_new = dijkstra_path_dup_shallow(path_b);
*paths = g_list_append(*paths, (gpointer) path_new);
dijkstra_disconnect_node_from_path(path_b, path_b->destination, 1);
dijkstra_connect_destination_node_to_path(node_new, path_b);
dijkstra_connect_source_node_to_path(node_new, path_new);
}
return 1;
}
return 0; // No collision
}
struct dijkstra_path *dijkstra_path_new_to_list(GList **nodes,
GList **paths,
float x1,
float y1,
float x2,
float y2,
char *name,
dijkstra_cost weight)
{
struct dijkstra_node *n1, *n2;
struct dijkstra_path *path;
struct dijkstra_path *existing_path;
GList *l, *l_last;
n1 = dijkstra_node_new_to_list(nodes, x1, y1, NULL);
n2 = dijkstra_node_new_to_list(nodes, x2, y2, NULL);
path = dijkstra_path_new(name, n1, n2, weight);
l_last = g_list_last(*paths);
*paths = g_list_append(*paths, (gpointer) path);
for (l = *paths; l != NULL; l = l->next) {
existing_path = (struct dijkstra_path*) l->data;
dijkstra_path_intersect(nodes, paths, path, existing_path);
if (l == l_last) /* Avoid testing newly added paths */
break;
}
return path;
}
/*!
* \brief dijkstra_node_new creates a new dijkstra_node
* \param x x position
* \param y y position
* \return a new dijkstra node or NULL. Needs to be freed manually.
*/
struct dijkstra_node *dijkstra_node_new(float x,
float y)
{
struct dijkstra_node *node;
node = malloc(sizeof(*node));
if (node) {
node->position.x = x;
node->position.y = y;
node->paths = NULL;
}
return node;
}
/*!
* \brief dijkstra_path_new creates a new dijkstra_path between two nodes.
* \param name the name of the path (pointer is not copied and must stay valid!)
* \return a new dijkstra path or NULL. Needs to be freed manually.
*/
struct dijkstra_path *dijkstra_path_new(char *name,
struct dijkstra_node *source,
struct dijkstra_node *destination,
dijkstra_cost weight)
{
struct dijkstra_path *path;
path = malloc(sizeof(*path));
if (path) {
path->name = name;
path->weight = weight;
dijkstra_connect_nodes_to_path(source, destination, path);
}
return path;
}

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#ifndef DIJKSTRASEARCH_H
#define DIJKSTRASEARCH_H
#include <glib.h>
typedef int dijkstra_cost;
struct position {
float x;
float y;
};
struct dijkstra_path {
struct dijkstra_node *source;
struct dijkstra_node *destination;
char *name;
dijkstra_cost weight;
};
struct dijkstra_node {
struct position position;
GList *paths;
dijkstra_cost cost;
};
struct dijkstra_node *dijkstra_node_new(float x,
float y);
struct dijkstra_path *dijkstra_path_new(char *name,
struct dijkstra_node *source,
struct dijkstra_node *destination,
dijkstra_cost weight);
int dijkstra_path_intersect(GList **nodes,
GList **paths,
struct dijkstra_path *path_a,
struct dijkstra_path *path_b);
struct dijkstra_path *dijkstra_path_new_to_list(GList **nodes,
GList **paths,
float x1,
float y1,
float x2,
float y2,
char *name,
dijkstra_cost weight);
#endif // DIJKSTRASEARCH_H

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#include <stdio.h>
#include "dijkstrasearch.h"
#include <glib/glist.h>
int main()
{
printf("Hello World!\n");
GList *nodes = NULL;
GList *paths = NULL;
GList *l = NULL;
struct dijkstra_node *node;
struct dijkstra_path *path;
dijkstra_path_new_to_list(&nodes,
&paths,
0,0,
0,10,
"Vertical",
1);
dijkstra_path_new_to_list(&nodes,
&paths,
0,5,
10,5,
"Horizontal",
1);
for (l = nodes; l != NULL; l = l->next) {
node = (struct dijkstra_node*) l->data;
printf("Node %p: %f,\t%f [%d paths]\n", node, node->position.x, node->position.y, g_list_length(node->paths));
}
printf("\n");
for (l = paths; l != NULL; l = l->next) {
path = (struct dijkstra_path*) l->data;
printf("Path %p: %p (%f,%f) -> %p (%f,%f) \t\"%s\"\n", path,
path->source, path->source->position.x, path->source->position.y,
path->destination, path->destination->position.x, path->destination->position.y,
path->name);
}
printf("\nDone.\n");
// TODO: Free memory
return 0;
}