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

use std::ops::{Mul, MulAssign, Neg};
mod vec3d;
pub use vec3d::Vec3D;
mod fast_rotate;
use fast_rotate::CachedRotation3D;

/// The `Transform3D` struct is used to manipulate the position of objects in 3D space
#[derive(Debug, Clone, Copy)]
pub struct Transform3D {
    /// The position of the object in 3D space
    pub translation: Vec3D,
    /// The rotation of the object, applied in radians
    pub rotation: Vec3D,
    /// The object's scale
    pub scale: Vec3D,
}

impl Default for Transform3D {
    fn default() -> Self {
        Self::DEFAULT
    }
}

impl Transform3D {
    /// The default transform - no translation, no rotation and 1x scaling
    pub const DEFAULT: Self = Self::new_trs(Vec3D::ZERO, Vec3D::ZERO, Vec3D::ONE);

    /// Create a `Transform3D` with chosen translation, rotation and scale
    #[must_use]
    pub const fn new_trs(translation: Vec3D, rotation: Vec3D, scale: Vec3D) -> Self {
        Self {
            translation,
            rotation,
            scale,
        }
    }

    /// Create a `Transform3D` with chosen translation and rotation
    #[must_use]
    pub const fn new_tr(translation: Vec3D, rotation: Vec3D) -> Self {
        Self {
            translation,
            rotation,
            scale: Vec3D::ONE,
        }
    }

    /// Create a `Transform3D` with chosen translation
    #[must_use]
    pub const fn new_t(translation: Vec3D) -> Self {
        Self {
            translation,
            rotation: Vec3D::ZERO,
            scale: Vec3D::ONE,
        }
    }

    /// Create a `Transform3D` with chosen rotation
    #[must_use]
    pub const fn new_r(rotation: Vec3D) -> Self {
        Self {
            translation: Vec3D::ZERO,
            rotation,
            scale: Vec3D::ONE,
        }
    }

    /// Apply the transform to a slice of vertices
    #[allow(clippy::let_and_return)]
    #[must_use]
    pub fn apply_to(&self, vertices: &[Vec3D]) -> Vec<Vec3D> {
        let rotation = CachedRotation3D::new(self.rotation);

        vertices
            .iter()
            .map(|v| {
                let rhs = *v;
                let rhs = rhs * self.scale;
                let rhs = rotation.rotate(rhs);
                let rhs = rhs + self.translation;

                rhs
            })
            .collect()
    }

    /// Apply the transform to a slice of vertices as if it is a viewport transform
    #[allow(clippy::let_and_return)]
    #[must_use]
    pub(crate) fn apply_viewport_transform(&self, vertices: &[Vec3D]) -> Vec<Vec3D> {
        let rotation = CachedRotation3D::new(-self.rotation);

        vertices
            .iter()
            .map(|v| {
                let rhs = *v;
                // Don't do scale at all
                let rhs = rhs - self.translation; // Translate before rotating
                let rhs = (rotation).rotate(rhs);

                rhs
            })
            .collect()
    }

    /// Rotate the given [`Vec3D`] using the `Transform3D`'s rotation field
    #[must_use]
    pub fn rotate(&self, value: Vec3D) -> Vec3D {
        let rotation = CachedRotation3D::new(self.rotation);

        rotation.rotate(value)
    }
}

impl Neg for Transform3D {
    type Output = Self;

    fn neg(self) -> Self::Output {
        Self::new_trs(-self.translation, -self.rotation, self.scale)
    }
}

impl Mul<Self> for Transform3D {
    type Output = Self;

    fn mul(self, rhs: Self) -> Self::Output {
        Self::new_trs(
            self.translation + rhs.translation,
            self.rotation + rhs.rotation,
            self.scale * rhs.scale,
        )
    }
}

impl MulAssign<Self> for Transform3D {
    fn mul_assign(&mut self, rhs: Self) {
        self.translation += rhs.translation;
        self.rotation += rhs.rotation;
        self.scale *= rhs.scale;
    }
}

impl Mul<Vec3D> for Transform3D {
    type Output = Vec3D;

    /// Apply the transform to the `Vec3D`
    #[allow(clippy::let_and_return)]
    fn mul(self, rhs: Vec3D) -> Self::Output {
        let rhs = rhs * self.scale;
        let rhs = self.rotate(rhs);
        let rhs = rhs + self.translation;

        rhs
    }
}