/* path.c - Path finding for Eurobot 2010. */ /* io - Input & Output with Artificial Intelligence (ai) support on AVR. {{{ * * Copyright (C) 2010 Nicolas Schodet * * APBTeam: * Web: http://apbteam.org/ * Email: team AT apbteam DOT org * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * }}} */ #include "common.h" #include "defs.h" #include "path.h" #include "food.h" #include "modules/path/astar/astar.h" #include "modules/utils/utils.h" #include "modules/math/geometry/distance.h" #define PATH_DEBUG 0 #if PATH_DEBUG #include "debug.host.h" #endif /** * This year, due to the large number of obstacles, a grid like structure is * used for path finding on the playground. The A* algorithm is used to find * path along nodes. * * The grid is composed of 13 columns of 5 node each. They are numbered by * column. See eurobot/2010/table for drawings of the grid. Even columns are * aligned with playing elements, while odd columns are connecting nodes * placed on the middle of segments connecting playing elements. Therefore, * odd columns have a offset of 125 mm, and that is the reason why code should * handle odd and even columns differently. * * All those tricks are used to reduce the number of nodes. */ /** Number of possible obstacles. */ #define PATH_OBSTACLES_NB AC_PATH_OBSTACLES_NB /** Number of nodes in a column. */ #define PATH_COLUMN_NODES_NB 5 /** Number of columns. */ #define PATH_COLUMNS_NB 13 /** Number of nodes in the grid. */ #define PATH_GRID_NODES_NB (PATH_COLUMNS_NB * PATH_COLUMN_NODES_NB) /** Number of nodes in search graph, last two nodes are destination and source * nodes. */ #define PATH_NODES_NB (PATH_GRID_NODES_NB + 2) /** Index of destination node. */ #define PATH_DST_NODE_INDEX PATH_GRID_NODES_NB /** Index of source node. */ #define PATH_SRC_NODE_INDEX (PATH_DST_NODE_INDEX + 1) /** Information on a node. */ struct path_node_t { /** Whether this node can be used. */ uint8_t usable; /** If this node can carry a corn, this is the index of the carried corn * in the food table, else, 0xff. */ uint8_t carry_corn; }; /** Context. */ struct path_t { /** List of obstacles. */ struct path_obstacle_t obstacles[PATH_OBSTACLES_NB]; /** List of nodes used for A*. */ struct astar_node_t astar_nodes[PATH_NODES_NB]; /** Cache of whether a node is blocked. */ uint8_t valid[PATH_GRID_NODES_NB]; /** Position of end points. */ vect_t endpoints[2]; /** Whether the last update was a success. */ uint8_t found; /** Which node to look at for next step. */ uint8_t get; }; static struct path_t path; /** Static information on nodes. */ static const struct path_node_t path_nodes[PATH_GRID_NODES_NB] = { /* {{{ */ { 1, 0 }, /* 0 column 0. */ { 1, 0xff }, /* 1 */ { 1, 2 }, /* 2 */ { 1, 0xff }, /* 3 */ { 1, 4 }, /* 4 */ { 1, 0xff }, /* 5 column 1. */ { 1, 0xff }, /* 6 */ { 1, 0xff }, /* 7 */ { 1, 0xff }, /* 8 */ { 1, 0xff }, /* 9 */ { 1, 0xff }, /* 10 column 2. */ { 1, 5 }, /* 11 */ { 1, 0xff }, /* 12 */ { 1, 7 }, /* 13 */ { 1, 0xff }, /* 14 */ { 1, 0xff }, /* 15 column 3. */ { 1, 0xff }, /* 16 */ { 1, 0xff }, /* 17 */ { 1, 0xff }, /* 18 */ { 1, 0xff }, /* 19 */ { 0, 0xff }, /* 20 column 4. */ { 1, 0xff }, /* 21 */ { 1, 10 }, /* 22 */ { 1, 0xff }, /* 23 */ { 1, 12 }, /* 24 */ { 1, 0xff }, /* 25 column 5. */ { 1, 0xff }, /* 26 */ { 1, 0xff }, /* 27 */ { 1, 0xff }, /* 28 */ { 1, 0xff }, /* 29 */ { 0, 0xff }, /* 30 column 6. */ { 1, 0xff }, /* 31 */ { 1, 0xff }, /* 32 */ { 1, 29 }, /* 33 */ { 1, 0xff }, /* 34 */ { 1, 0xff }, /* 35 column 7. */ { 1, 0xff }, /* 36 */ { 1, 0xff }, /* 37 */ { 1, 0xff }, /* 38 */ { 1, 0xff }, /* 39 */ { 0, 0xff }, /* 40 column 8. */ { 1, 0xff }, /* 41 */ { 1, 24 }, /* 42 */ { 1, 0xff }, /* 43 */ { 1, 26 }, /* 44 */ { 1, 0xff }, /* 45 column 9. */ { 1, 0xff }, /* 46 */ { 1, 0xff }, /* 47 */ { 1, 0xff }, /* 48 */ { 1, 0xff }, /* 49 */ { 1, 0xff }, /* 50 column 10. */ { 1, 19 }, /* 51 */ { 1, 0xff }, /* 52 */ { 1, 21 }, /* 53 */ { 1, 0xff }, /* 54 */ { 1, 0xff }, /* 55 column 11. */ { 1, 0xff }, /* 56 */ { 1, 0xff }, /* 57 */ { 1, 0xff }, /* 58 */ { 1, 0xff }, /* 59 */ { 1, 14 }, /* 60 column 12. */ { 1, 0xff }, /* 61 */ { 1, 16 }, /* 62 */ { 1, 0xff }, /* 63 */ { 1, 18 }, /* 64 */ /* }}} */ }; /** Compute position of a node. */ static void path_pos (uint8_t node, vect_t *pos) { assert (node < PATH_NODES_NB); if (node < PATH_GRID_NODES_NB) { uint8_t col = node / PATH_COLUMN_NODES_NB; uint8_t line = node - col * PATH_COLUMN_NODES_NB; pos->x = 150 + col * 450 / 2; pos->y = 128 + PATH_COLUMN_NODES_NB * 250 - (col % 2 ? 250 / 2 : 0) - line * 250; } else { *pos = path.endpoints[node - PATH_GRID_NODES_NB]; } } /** Return 1 if the direct path between a and b nodes is blocked, also compute * distance. */ static uint8_t path_blocking (uint8_t a, uint8_t b, int16_t *dp) { uint8_t i; vect_t va; vect_t vb; path_pos (a, &va); path_pos (b, &vb); /* Test for a blocking obstacle. */ for (i = 0; i < PATH_OBSTACLES_NB; i++) { if (path.obstacles[i].valid) { uint16_t d = distance_segment_point (&va, &vb, &path.obstacles[i].c); if (d < path.obstacles[i].r) return 1; } } /* Test for a blocking food. */ int16_t d = distance_point_point (&va, &vb); *dp = d; if (d == 0) return 0; return food_blocking_path (va, vb, d); } /** Update the cache of blocked nodes. */ static void path_blocked_update (void) { uint8_t i, j; for (i = 0; i < PATH_GRID_NODES_NB; i++) { uint8_t valid = 1; /* First, gather information from tables. */ if (!path_nodes[i].usable || food_blocking (path_nodes[i].carry_corn)) valid = 0; else { vect_t pos; path_pos (i, &pos); /* Then, test for obstacles. */ for (j = 0; j < PATH_OBSTACLES_NB; j++) { if (path.obstacles[j].valid) { vect_t v = pos; vect_sub (&v, &path.obstacles[j].c); uint32_t dsq = vect_dot_product (&v, &v); uint32_t r = path.obstacles[j].r; if (dsq <= r * r) { valid = 0; break; } } } } /* Update cache. */ path.valid[i] = valid; } } void path_init (int16_t border_xmin, int16_t border_ymin, int16_t border_xmax, int16_t border_ymax) { /* Border are ignored as only the grid is used, nothing else to do. */ } void path_endpoints (vect_t s, vect_t d) { path.endpoints[0] = d; path.endpoints[1] = s; } void path_escape (uint8_t factor) { /* TODO */ } void path_obstacle (uint8_t i, vect_t c, uint16_t r, uint8_t factor, uint16_t valid) { assert (i < AC_PATH_OBSTACLES_NB); assert (factor == 0); path.obstacles[i].c = c; path.obstacles[i].r = r; path.obstacles[i].valid = valid; } void path_decay (void) { uint8_t i; for (i = 0; i < PATH_OBSTACLES_NB; i++) { if (path.obstacles[i].valid && path.obstacles[i].valid != PATH_OBSTACLE_VALID_ALWAYS) path.obstacles[i].valid--; } } void path_update (void) { path_blocked_update (); path.found = astar (path.astar_nodes, PATH_NODES_NB, PATH_DST_NODE_INDEX, PATH_SRC_NODE_INDEX); path.get = PATH_SRC_NODE_INDEX; #if AC_PATH_REPORT if (path.found) { uint8_t n, len = 0; vect_t points[PATH_NODES_NB]; for (n = path.get; n != PATH_DST_NODE_INDEX; n = path.astar_nodes[n].prev) path_pos (n, &points[len++]); path_pos (n, &points[len++]); AC_PATH_REPORT_CALLBACK (points, len, path.obstacles, PATH_OBSTACLES_NB); } #endif } uint8_t path_get_next (vect_t *p) { if (path.found) { /* TODO: remove useless nodes. */ assert (path.get != PATH_DST_NODE_INDEX); uint8_t next = path.astar_nodes[path.get].prev; path.get = next; path_pos (next, p); return 1; } else return 0; } /** Neighbors callback for nodes in grid. */ static uint8_t path_astar_neighbor_callback_grid (uint8_t node, struct astar_neighbor_t *neighbors) { uint8_t neighbors_nb = 0; uint8_t i; /* Add neighbors in all 6 directions. */ static const struct { /** Column offset of this neighbor. */ int8_t column_offset; /** Line offset of this neighbor. */ int8_t line_offset; /** Extra line offset for odd columns. */ int8_t odd_line_offset; /** Distance to this neighbor. */ uint16_t weight; } star_n[] = { { 0, -1, 0, 250 }, /* N */ { -1, -1, 1, 514 / 2 }, /* NW */ { -1, 0, 1, 514 / 2 }, /* SW */ { 0, 1, 0, 250 }, /* S */ { 1, 0, 1, 514 / 2 }, /* SE */ { 1, -1, 1, 514 / 2 }, /* NE */ }; uint8_t col = node / PATH_COLUMN_NODES_NB; uint8_t line = node - col * PATH_COLUMN_NODES_NB; uint8_t odd = col % 2; for (i = 0; i < UTILS_COUNT (star_n); i++) { int8_t new_col = col + star_n[i].column_offset; int8_t new_line = line + star_n[i].line_offset + (odd ? star_n[i].odd_line_offset : 0); int8_t new_node = new_col * PATH_COLUMN_NODES_NB + new_line; if (new_col >= 0 && new_col < PATH_COLUMNS_NB && new_line >= 0 && new_line < PATH_COLUMN_NODES_NB && path.valid[new_node]) { neighbors[neighbors_nb].node = new_node; neighbors[neighbors_nb].weight = star_n[i].weight + 1; neighbors_nb++; } } /* Check if direct path OK. */ int16_t d; if (!path_blocking (node, PATH_SRC_NODE_INDEX, &d)) { /* Add this neighbor. */ neighbors[neighbors_nb].node = PATH_SRC_NODE_INDEX; neighbors[neighbors_nb].weight = d + 1; neighbors_nb++; } #if PATH_DEBUG for (i = 0; i < neighbors_nb; i++) DPRINTF (" n %d %d\n", neighbors[i].node, neighbors[i].weight); #endif return neighbors_nb; } /** Neighbors callback for endpoints. */ static uint8_t path_astar_neighbor_callback_endpoints (uint8_t node, struct astar_neighbor_t *neighbors) { uint8_t neighbors_nb = 0; uint8_t i; assert (node == PATH_DST_NODE_INDEX); /* Select neighbors in the grid. */ for (i = 0; i < PATH_GRID_NODES_NB; i++) { /* Discard blocking nodes. */ if (!path.valid[i]) continue; /* Check if there is an obstacle along the path. */ int16_t d; if (path_blocking (PATH_DST_NODE_INDEX, i, &d)) continue; /* Add this neighbor. */ neighbors[neighbors_nb].node = i; neighbors[neighbors_nb].weight = d + 1; neighbors_nb++; } /* Check if direct path OK. */ int16_t d; if (!path_blocking (PATH_DST_NODE_INDEX, PATH_SRC_NODE_INDEX, &d)) { /* Add this neighbor. */ neighbors[neighbors_nb].node = PATH_SRC_NODE_INDEX; neighbors[neighbors_nb].weight = d + 1; neighbors_nb++; } #if PATH_DEBUG for (i = 0; i < neighbors_nb; i++) DPRINTF (" n %d %d\n", neighbors[i].node, neighbors[i].weight); #endif return neighbors_nb; } uint8_t path_astar_neighbor_callback (uint8_t node, struct astar_neighbor_t *neighbors) { #if PATH_DEBUG DPRINTF ("neighbor %d\n", node); #endif if (node < PATH_GRID_NODES_NB) return path_astar_neighbor_callback_grid (node, neighbors); else return path_astar_neighbor_callback_endpoints (node, neighbors); } uint16_t path_astar_heuristic_callback (uint8_t node) { /* TODO: a better and faster heuristic can be found, considering that * movement is only allowed on the grid. */ vect_t pos; path_pos (node, &pos); return distance_point_point (&pos, &path.endpoints[0]); }