bevy_render/render_phase/
rangefinder.rs

1use bevy_math::{Affine3A, 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: &Affine3A) -> ViewRangefinder3d {
11        let view_from_world = world_from_view.inverse();
12
13        ViewRangefinder3d {
14            view_from_world_row_2: Mat4::from(view_from_world).row(2),
15        }
16    }
17
18    /// Calculates the distance, or view-space `Z` value, for the given world-space `position`.
19    #[inline]
20    pub fn distance(&self, position: &Vec3) -> f32 {
21        // NOTE: row 2 of the inverse view matrix dotted with the world-space position
22        // gives the z component of the point in view-space
23        self.view_from_world_row_2.dot(position.extend(1.0))
24    }
25}
26
27#[cfg(test)]
28mod tests {
29    use super::ViewRangefinder3d;
30    use bevy_math::{Affine3A, Vec3};
31
32    #[test]
33    fn distance() {
34        let view_matrix = Affine3A::from_translation(Vec3::new(0.0, 0.0, -1.0));
35        let rangefinder = ViewRangefinder3d::from_world_from_view(&view_matrix);
36        assert_eq!(rangefinder.distance(&Vec3::new(0., 0., 0.)), 1.0);
37        assert_eq!(rangefinder.distance(&Vec3::new(0., 0., 1.)), 2.0);
38    }
39}
bevy_render/render_phase/rangefinder.rs

bevy_render/render_phase/
rangefinder.rs
