marss 0.0.3

Mars celestial simulation crate for the MilkyWay SolarSystem workspace
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

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Face {
    PosX,
    NegX,
    PosY,
    NegY,
    PosZ,
    NegZ,
}

pub struct QuadTreeNode {
    pub face: Face,
    pub level: u32,
    pub x: u32,
    pub y: u32,
    pub children: Option<Box<[QuadTreeNode; 4]>>,
}

impl QuadTreeNode {
    pub fn new(face: Face, level: u32, x: u32, y: u32) -> Self {
        Self {
            face,
            level,
            x,
            y,
            children: None,
        }
    }

    pub fn is_leaf(&self) -> bool {
        self.children.is_none()
    }

    pub fn center_on_sphere(&self, radius: f64) -> (f64, f64, f64) {
        let size = 1.0 / (1u32 << self.level) as f64;
        let cx = self.x as f64 * size + size * 0.5;
        let cy = self.y as f64 * size + size * 0.5;
        let (u, v) = (cx * 2.0 - 1.0, cy * 2.0 - 1.0);
        let (x, y, z) = match self.face {
            Face::PosX => (1.0, v, -u),
            Face::NegX => (-1.0, v, u),
            Face::PosY => (u, 1.0, -v),
            Face::NegY => (u, -1.0, v),
            Face::PosZ => (u, v, 1.0),
            Face::NegZ => (-u, v, -1.0),
        };
        let len = (x * x + y * y + z * z).sqrt();
        (x / len * radius, y / len * radius, z / len * radius)
    }
}

pub struct LodConfig {
    pub max_level: u32,
    pub split_distance_factor: f64,
}

impl Default for LodConfig {
    fn default() -> Self {
        Self {
            max_level: 14,
            split_distance_factor: 2.0,
        }
    }
}

pub struct LodTerrain {
    pub roots: Vec<QuadTreeNode>,
    pub config: LodConfig,
}

impl LodTerrain {
    pub fn new(config: LodConfig) -> Self {
        let faces = [
            Face::PosX,
            Face::NegX,
            Face::PosY,
            Face::NegY,
            Face::PosZ,
            Face::NegZ,
        ];
        let roots = faces
            .into_iter()
            .map(|f| QuadTreeNode::new(f, 0, 0, 0))
            .collect();
        Self { roots, config }
    }

    pub fn update(&mut self, camera: (f64, f64, f64)) {
        for root in &mut self.roots {
            Self::update_node(root, camera, crate::MARS_RADIUS, &self.config);
        }
    }

    fn update_node(
        node: &mut QuadTreeNode,
        camera: (f64, f64, f64),
        radius: f64,
        config: &LodConfig,
    ) {
        if node.level >= config.max_level {
            return;
        }
        let center = node.center_on_sphere(radius);
        let dx = camera.0 - center.0;
        let dy = camera.1 - center.1;
        let dz = camera.2 - center.2;
        let dist = (dx * dx + dy * dy + dz * dz).sqrt();

        let size = radius * 2.0 / (1u32 << node.level) as f64;
        if dist < size * config.split_distance_factor {
            if node.children.is_none() {
                let l = node.level + 1;
                let bx = node.x * 2;
                let by = node.y * 2;
                node.children = Some(Box::new([
                    QuadTreeNode::new(node.face, l, bx, by),
                    QuadTreeNode::new(node.face, l, bx + 1, by),
                    QuadTreeNode::new(node.face, l, bx, by + 1),
                    QuadTreeNode::new(node.face, l, bx + 1, by + 1),
                ]));
            }
            if let Some(ref mut children) = node.children {
                for child in children.iter_mut() {
                    Self::update_node(child, camera, radius, config);
                }
            }
        } else {
            node.children = None;
        }
    }

    pub fn leaf_count(&self) -> usize {
        self.roots.iter().map(Self::count_leaves).sum()
    }

    fn count_leaves(node: &QuadTreeNode) -> usize {
        match &node.children {
            None => 1,
            Some(children) => children.iter().map(Self::count_leaves).sum(),
        }
    }
}