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

use glam::{const_mat3a, Mat3A};

/// Default orientation matrix.
pub const EYE: Mat3A = const_mat3a!([1., 0., 0.], [0., 1., 0.], [0., 0., 1.]);

pub(crate) trait MatrixExt {
    fn dot(&self, other: Self) -> Self;
    fn denom(&self, other: f32) -> Self;
}

impl MatrixExt for Mat3A {
    fn dot(&self, other: Self) -> Self {
        // For some reason, glam does matrix multiplication in column order. So,
        // we have to transpose both matrices prior to multiplying them. Then,
        // transpose the final result.
        (self.transpose() * other.transpose()).transpose()
    }

    fn denom(&self, other: f32) -> Self {
        Self::from_cols(self.x_axis / other, self.y_axis / other, self.z_axis / other)
    }
}

#[cfg(test)]
mod test {

    use glam::{const_mat3a, Mat3A};

    use crate::linear_algebra::mat::MatrixExt;

    const A: Mat3A = const_mat3a!([-1., 2., 3.], [4., 5., 6.], [7., 8., 9.]);
    const B: Mat3A = const_mat3a!([9., 8., 7.], [6., -5., 4.], [3., 2., 1.]);
    const C: Mat3A = const_mat3a!([12.0, -12.0, 4.0], [84.0, 19.0, 54.0], [138.0, 34.0, 90.0]);

    #[test]
    fn mat3_dot() {
        assert_eq!(A.dot(B), C);
    }
}