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/* SPDX-License-Identifier: GPL-2.0-or-later
* Copyright 2014 Blender Foundation. All rights reserved. */
#pragma once
/** \file
* \ingroup bli
* \brief An implementation of the A* (AStar) algorithm to solve shortest path problem.
*/
#include "BLI_utildefines.h"
#include "BLI_bitmap.h"
#ifdef __cplusplus
extern "C" {
#endif
/* -------------------------------------------------------------------- */
typedef struct BLI_AStarGNLink {
int nodes[2];
float cost;
void *custom_data;
} BLI_AStarGNLink;
typedef struct BLI_AStarGNode {
struct ListBase neighbor_links;
void *custom_data;
} BLI_AStarGNode;
typedef struct BLI_AStarSolution {
/* Final 'most useful' data. */
/** Number of steps (i.e. walked links) in path
* (nodes num, including start and end, is steps + 1). */
int steps;
/** Store the path, in reversed order (from destination to source node), as indices. */
int *prev_nodes;
/** Indices are nodes' ones, as prev_nodes, but they map to relevant link. */
BLI_AStarGNLink **prev_links;
void *custom_data;
/* Mostly runtime data. */
BLI_bitmap *done_nodes;
float *g_costs;
int *g_steps;
struct MemArena *mem; /* Memory arena. */
} BLI_AStarSolution;
typedef struct BLI_AStarGraph {
int node_num;
BLI_AStarGNode *nodes;
void *custom_data;
struct MemArena *mem; /* Memory arena. */
} BLI_AStarGraph;
/**
* Initialize a node in A* graph.
*
* \param custom_data: an opaque pointer attached to this link,
* available e.g. to cost callback function.
*/
void BLI_astar_node_init(BLI_AStarGraph *as_graph, int node_index, void *custom_data);
/**
* Add a link between two nodes of our A* graph.
*
* \param cost: The 'length' of the link
* (actual distance between two vertices or face centers e.g.).
* \param custom_data: An opaque pointer attached to this link,
* available e.g. to cost callback function.
*/
void BLI_astar_node_link_add(
BLI_AStarGraph *as_graph, int node1_index, int node2_index, float cost, void *custom_data);
/**
* \return The index of the other node of given link.
*/
int BLI_astar_node_link_other_node(BLI_AStarGNLink *lnk, int idx);
/**
* Initialize a solution data for given A* graph. Does not compute anything!
*
* \param custom_data: an opaque pointer attached to this link, available e.g
* . to cost callback function.
*
* \note BLI_AStarSolution stores nearly all data needed during solution compute.
*/
void BLI_astar_solution_init(BLI_AStarGraph *as_graph,
BLI_AStarSolution *as_solution,
void *custom_data);
/**
* Clear given solution's data, but does not release its memory.
* Avoids having to recreate/allocate a memarena in loops, e.g.
*
* \note This *has to be called* between each path solving.
*/
void BLI_astar_solution_clear(BLI_AStarSolution *as_solution);
/**
* Release the memory allocated for this solution.
*/
void BLI_astar_solution_free(BLI_AStarSolution *as_solution);
/**
* Callback computing the current cost (distance) to next node,
* and the estimated overall cost to destination node
* (A* expects this estimation to always be less or equal than actual shortest path
* from next node to destination one).
*
* \param link: the graph link between current node and next one.
* \param node_idx_curr: current node index.
* \param node_idx_next: next node index.
* \param node_idx_dst: destination node index.
*/
typedef float (*astar_f_cost)(BLI_AStarGraph *as_graph,
BLI_AStarSolution *as_solution,
BLI_AStarGNLink *link,
int node_idx_curr,
int node_idx_next,
int node_idx_dst);
/**
* Initialize an A* graph. Total number of nodes must be known.
*
* Nodes might be e.g. vertices, faces, ... etc.
*
* \param custom_data: an opaque pointer attached to this link,
* available e.g. to cost callback function.
*/
void BLI_astar_graph_init(BLI_AStarGraph *as_graph, int node_num, void *custom_data);
void BLI_astar_graph_free(BLI_AStarGraph *as_graph);
/**
* Solve a path in given graph, using given 'cost' callback function.
*
* \param max_steps: maximum number of nodes the found path may have.
* Useful in performance-critical usages.
* If no path is found within given steps, returns false too.
* \return true if a path was found, false otherwise.
*/
bool BLI_astar_graph_solve(BLI_AStarGraph *as_graph,
int node_index_src,
int node_index_dst,
astar_f_cost f_cost_cb,
BLI_AStarSolution *r_solution,
int max_steps);
#ifdef __cplusplus
}
#endif
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