use bevy_math::{Mat4, Vec4};
pub struct ViewRangefinder3d {
inverse_view_row_2: Vec4,
}
impl ViewRangefinder3d {
pub fn from_view_matrix(view_matrix: &Mat4) -> ViewRangefinder3d {
let inverse_view_matrix = view_matrix.inverse();
ViewRangefinder3d {
inverse_view_row_2: inverse_view_matrix.row(2),
}
}
#[inline]
pub fn distance(&self, transform: &Mat4) -> f32 {
self.inverse_view_row_2.dot(transform.col(3))
}
}
#[cfg(test)]
mod tests {
use super::ViewRangefinder3d;
use bevy_math::{Mat4, Vec3};
#[test]
fn distance() {
let view_matrix = Mat4::from_translation(Vec3::new(0.0, 0.0, -1.0));
let rangefinder = ViewRangefinder3d::from_view_matrix(&view_matrix);
assert_eq!(rangefinder.distance(&Mat4::IDENTITY), 1.0);
assert_eq!(
rangefinder.distance(&Mat4::from_translation(Vec3::new(0.0, 0.0, 1.0))),
2.0
);
}
}