rust_training_tool/
collision.rs

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
//! Simple collision resolution logic.

use eframe::egui::{Rect, Vec2};

/// The direction in which an object colliding with something should bounce.
#[derive(Debug, Eq, PartialEq, Hash)]
pub enum BounceDirection {
    Up,
    Left,
    Down,
    Right,
}

/// A function to check collision between some moving object with a bounding box and the
/// edges of some boundary. If the boundary rectangle does not fully contain
/// the bounding box, return the direction the object must bounce to stay within
/// the boundary.
///
/// ### Example
///
/// ```
/// use rust_training_tool::collision;
/// use rust_training_tool::egui::{Pos2, Rect, Vec2};
/// let boundary = Rect::from_center_size(Pos2::ZERO, Vec2::new(10.0, 10.0));
///
/// // boundary box is inside the boundary rect
/// let mut bounding_box = Rect::from_center_size(Pos2::ZERO, Vec2::new(1.0, 1.0));
/// assert!(collision::collide_with_boundary(&bounding_box, &boundary).is_none());
///
/// // move bounding box so it intersects the boundary on the right
/// bounding_box.set_center(Pos2::new(9.1, 0.0));
/// assert!(matches!(
///     collision::collide_with_boundary(&bounding_box, &boundary),
///     Some(collision::BounceDirection::Left)
/// ));
/// ```
pub fn collide_with_boundary(bounding_box: &Rect, boundary: &Rect) -> Option<BounceDirection> {
    if !boundary.contains_rect(*bounding_box) {
        if bounding_box.left() < boundary.left() {
            Some(BounceDirection::Right)
        } else if bounding_box.right() > boundary.right() {
            Some(BounceDirection::Left)
        } else if bounding_box.top() < boundary.top() {
            Some(BounceDirection::Down)
        } else if bounding_box.bottom() > boundary.bottom() {
            Some(BounceDirection::Up)
        } else {
            eprintln!("WARNING: outside but not colliding?");
            None
        }
    } else {
        None
    }
}

/// A function to check collision between an object moving in `self_direction` with a bounding box
/// `self_bounding_box`, and some other bounding box. If bounding boxes intersect,
/// return the direction the moving object should bounce, otherwise, return None.
///
/// ### Example
///
/// ```
/// use rust_training_tool::collision;
/// use rust_training_tool::egui::{Pos2, Rect, Vec2};
///
/// // I am moving up
/// let self_direction = -Vec2::Y;
/// let self_bounding_box = Rect::from_center_size(Pos2::ZERO, Vec2::new(1.0, 1.0));
/// let other_bounding_box = Rect::from_center_size(
///     Pos2::new(1.0, 0.9),
///     Vec2::new(1.0, 1.0),
/// );
/// assert!(matches!(
///     collision::collide_with_rect(
///         &self_direction,
///         &self_bounding_box,
///         &other_bounding_box
///     ),
///     Some(collision::BounceDirection::Down)
/// ));
///
/// // I am moving right
/// let self_direction = Vec2::X;
/// let other_bounding_box = Rect::from_center_size(
///     Pos2::new(0.9, 1.0),
///     Vec2::new(1.0, 1.0),
/// );
/// assert!(matches!(
///     collision::collide_with_rect(
///         &self_direction,
///         &self_bounding_box,
///         &other_bounding_box
///     ),
///     Some(collision::BounceDirection::Left)
/// ));
/// ```
pub fn collide_with_rect(
    self_direction: &Vec2,
    self_bounding_box: &Rect,
    other_bounding_box: &Rect,
) -> Option<BounceDirection> {
    if self_bounding_box.intersects(*other_bounding_box) {
        let inside_bottom = -(self_bounding_box.top() - other_bounding_box.bottom());
        let inside_right = -(self_bounding_box.left() - other_bounding_box.right());
        let inside_left = self_bounding_box.right() - other_bounding_box.left();
        let inside_top = self_bounding_box.bottom() - other_bounding_box.top();

        let mut min_in: f32 = 999.0;
        if inside_bottom >= 0.0 && self_direction.y < 0.0 {
            min_in = min_in.min(inside_bottom);
        }
        if inside_right >= 0.0 && self_direction.x < 0.0 {
            min_in = min_in.min(inside_right);
        }
        if inside_left >= 0.0 && self_direction.x > 0.0 {
            min_in = min_in.min(inside_left);
        }
        if inside_top >= 0.0 && self_direction.y > 0.0 {
            min_in = min_in.min(inside_top);
        }

        if min_in == inside_bottom {
            Some(BounceDirection::Down)
        } else if min_in == inside_right {
            Some(BounceDirection::Right)
        } else if min_in == inside_left {
            Some(BounceDirection::Left)
        } else if min_in == inside_top {
            Some(BounceDirection::Up)
        } else {
            eprintln!("WARNING: colliding but not inside?");
            None
        }
    } else {
        None
    }
}