rerecast 0.3.2

Rust port of recastnavigation
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197

//! Watershed partitioning
//!   - the classic Recast partitioning
//!   - creates the nicest tessellation
//!   - usually slowest
//!   - partitions the heightfield into nice regions without holes or overlaps
//!   - the are some corner cases where this method creates produces holes and overlaps
//!      - holes may appear when a small obstacles is close to large open area (triangulation can handle this)
//!      - overlaps may occur if you have narrow spiral corridors (i.e stairs), this make triangulation to fail
//!   * generally the best choice if you precompute the navmesh, use this if you have large open areas

use alloc::vec::Vec;

use crate::{
    CompactHeightfield,
    math::{dir_offset_x, dir_offset_z},
};

impl CompactHeightfield {
    /// Prepare for region partitioning, by calculating distance field along the walkable surface.
    pub fn build_distance_field(&mut self) {
        let distance_field = self.calculate_distance_field();
        self.max_distance = distance_field.iter().max().copied().unwrap_or_default();
        let distance_field = self.box_blur(1, &distance_field);
        self.dist = distance_field;
    }

    fn calculate_distance_field(&self) -> Vec<u16> {
        // Init distance and points.
        let mut distance_field = vec![u16::MAX; self.spans.len()];

        // Mark boundary cells.
        for z in 0..self.height {
            for x in 0..self.width {
                let cell = self.cell_at(x, z);
                let max_index = cell.index() as usize + cell.count() as usize;
                #[expect(
                    clippy::needless_range_loop,
                    reason = "lol the alternative suggestion is really unreadable"
                )]
                for i in cell.index() as usize..max_index {
                    let span = &self.spans[i];
                    let area = self.areas[i];

                    let mut connection_count = 0;
                    for dir in 0..4 {
                        if let Some(con) = span.con(dir) {
                            let a_x = (x as i32 + dir_offset_x(dir) as i32) as u16;
                            let a_z = (z as i32 + dir_offset_z(dir) as i32) as u16;
                            let a_index = self.cell_at(a_x, a_z).index() as usize + con as usize;
                            if area == self.areas[a_index] {
                                connection_count += 1;
                            }
                        }
                    }
                    if connection_count < 4 {
                        distance_field[i] = 0;
                    }
                }
            }
        }

        // Pass 1
        for z in 0..self.height {
            for x in 0..self.width {
                let cell = self.cell_at(x, z);
                let max_index = cell.index() as usize + cell.count() as usize;
                for i in cell.index() as usize..max_index {
                    let span = &self.spans[i];
                    if let Some(con) = span.con(0) {
                        // (-1,0)
                        let a_x = (x as i32 + dir_offset_x(0) as i32) as u16;
                        let a_z = (z as i32 + dir_offset_z(0) as i32) as u16;
                        let a_index = self.cell_at(a_x, a_z).index() as usize + con as usize;
                        let a_span = &self.spans[a_index];
                        distance_field[i] = distance_field[i].min(distance_field[a_index] + 2);

                        // (-1,-1)
                        if let Some(con) = a_span.con(3) {
                            let b_x = (a_x as i32 + dir_offset_x(3) as i32) as u16;
                            let b_z = (a_z as i32 + dir_offset_z(3) as i32) as u16;
                            let b_index = self.cell_at(b_x, b_z).index() as usize + con as usize;
                            distance_field[i] = distance_field[i].min(distance_field[b_index] + 3);
                        }
                    }

                    if let Some(con) = span.con(3) {
                        // (0, -1)
                        let a_x = (x as i32 + dir_offset_x(3) as i32) as u16;
                        let a_z = (z as i32 + dir_offset_z(3) as i32) as u16;
                        let a_index = self.cell_at(a_x, a_z).index() as usize + con as usize;
                        let a_span = &self.spans[a_index];
                        distance_field[i] = distance_field[i].min(distance_field[a_index] + 2);

                        // (1, -1)
                        if let Some(con) = a_span.con(2) {
                            let b_x = (a_x as i32 + dir_offset_x(2) as i32) as u16;
                            let b_z = (a_z as i32 + dir_offset_z(2) as i32) as u16;
                            let b_index = self.cell_at(b_x, b_z).index() as usize + con as usize;
                            distance_field[i] = distance_field[i].min(distance_field[b_index] + 3);
                        }
                    }
                }
            }
        }

        // Pass 2
        for z in (0..self.height).rev() {
            for x in (0..self.width).rev() {
                let cell = self.cell_at(x, z);
                let max_index = cell.index() as usize + cell.count() as usize;
                for i in cell.index() as usize..max_index {
                    let span = &self.spans[i];
                    if let Some(con) = span.con(2) {
                        // (1, 0)
                        let a_x = (x as i32 + dir_offset_x(2) as i32) as u16;
                        let a_z = (z as i32 + dir_offset_z(2) as i32) as u16;
                        let a_index = self.cell_at(a_x, a_z).index() as usize + con as usize;
                        let a_span = &self.spans[a_index];
                        distance_field[i] = distance_field[i].min(distance_field[a_index] + 2);

                        // (1, 1)
                        if let Some(con) = a_span.con(1) {
                            let b_x = (a_x as i32 + dir_offset_x(1) as i32) as u16;
                            let b_z = (a_z as i32 + dir_offset_z(1) as i32) as u16;
                            let b_index = self.cell_at(b_x, b_z).index() as usize + con as usize;
                            distance_field[i] = distance_field[i].min(distance_field[b_index] + 3);
                        }
                    }

                    if let Some(con) = span.con(1) {
                        // (0, 1)
                        let a_x = (x as i32 + dir_offset_x(1) as i32) as u16;
                        let a_z = (z as i32 + dir_offset_z(1) as i32) as u16;
                        let a_index = self.cell_at(a_x, a_z).index() as usize + con as usize;
                        let a_span = &self.spans[a_index];
                        distance_field[i] = distance_field[i].min(distance_field[a_index] + 2);

                        // (-1, 1)
                        if let Some(con) = a_span.con(0) {
                            let b_x = (a_x as i32 + dir_offset_x(0) as i32) as u16;
                            let b_z = (a_z as i32 + dir_offset_z(0) as i32) as u16;
                            let b_index = self.cell_at(b_x, b_z).index() as usize + con as usize;
                            distance_field[i] = distance_field[i].min(distance_field[b_index] + 3);
                        }
                    }
                }
            }
        }

        distance_field
    }

    fn box_blur(&self, threshold: u16, distance_field: &[u16]) -> Vec<u16> {
        let threshold = threshold.saturating_mul(2);
        let mut result = vec![0; distance_field.len()];

        for z in 0..self.height {
            for x in 0..self.width {
                let cell = self.cell_at(x, z);
                let max_index = cell.index() as usize + cell.count() as usize;
                for i in cell.index() as usize..max_index {
                    let span = &self.spans[i];
                    let cd = distance_field[i];
                    if cd <= threshold {
                        result[i] = cd;
                        continue;
                    }
                    let mut d = cd as u32;
                    for dir in 0..4 {
                        if let Some(con) = span.con(dir) {
                            let a_x = (x as i32 + dir_offset_x(dir) as i32) as u16;
                            let a_z = (z as i32 + dir_offset_z(dir) as i32) as u16;
                            let a_index = self.cell_at(a_x, a_z).index() as usize + con as usize;
                            d += distance_field[a_index] as u32;

                            let a_span = &self.spans[a_index];
                            let dir2 = (dir + 1) & 0x3;
                            if let Some(con) = a_span.con(dir2) {
                                let b_x = (a_x as i32 + dir_offset_x(dir2) as i32) as u16;
                                let b_z = (a_z as i32 + dir_offset_z(dir2) as i32) as u16;
                                let b_index =
                                    self.cell_at(b_x, b_z).index() as usize + con as usize;
                                d += distance_field[b_index] as u32;
                            } else {
                                d += cd as u32;
                            }
                        } else {
                            d += cd as u32 * 2;
                        }
                    }
                    result[i] = ((d + 5) / 9) as u16;
                }
            }
        }
        result
    }
}