bevy_render/render_phase/
rangefinder.rs

1use bevy_math::{Mat4, Vec3, Vec4};
2
3/// A distance calculator for the draw order of [`PhaseItem`](crate::render_phase::PhaseItem)s.
4pub struct ViewRangefinder3d {
5    view_from_world_row_2: Vec4,
6}
7
8impl ViewRangefinder3d {
9    /// Creates a 3D rangefinder for a view matrix.
10    pub fn from_world_from_view(world_from_view: &Mat4) -> ViewRangefinder3d {
11        let view_from_world = world_from_view.inverse();
12
13        ViewRangefinder3d {
14            view_from_world_row_2: view_from_world.row(2),
15        }
16    }
17
18    /// Calculates the distance, or view-space `Z` value, for the given `translation`.
19    #[inline]
20    pub fn distance_translation(&self, translation: &Vec3) -> f32 {
21        // NOTE: row 2 of the inverse view matrix dotted with the translation from the model matrix
22        // gives the z component of translation of the mesh in view-space
23        self.view_from_world_row_2.dot(translation.extend(1.0))
24    }
25
26    /// Calculates the distance, or view-space `Z` value, for the given `transform`.
27    #[inline]
28    pub fn distance(&self, transform: &Mat4) -> f32 {
29        // NOTE: row 2 of the inverse view matrix dotted with column 3 of the model matrix
30        // gives the z component of translation of the mesh in view-space
31        self.view_from_world_row_2.dot(transform.col(3))
32    }
33}
34
35#[cfg(test)]
36mod tests {
37    use super::ViewRangefinder3d;
38    use bevy_math::{Mat4, Vec3};
39
40    #[test]
41    fn distance() {
42        let view_matrix = Mat4::from_translation(Vec3::new(0.0, 0.0, -1.0));
43        let rangefinder = ViewRangefinder3d::from_world_from_view(&view_matrix);
44        assert_eq!(rangefinder.distance(&Mat4::IDENTITY), 1.0);
45        assert_eq!(
46            rangefinder.distance(&Mat4::from_translation(Vec3::new(0.0, 0.0, 1.0))),
47            2.0
48        );
49    }
50}
bevy_render/render_phase/rangefinder.rs

bevy_render/render_phase/
rangefinder.rs
