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https://github.com/bevyengine/bevy
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93a131661d
# Objective - Added a bunch of backticks to things that should have them, like equations, abstract variable names, - Changed all small x, y, and z to capitals X, Y, Z. This might be more annoying than helpful; Feel free to refuse this PR.
41 lines
1.3 KiB
Rust
41 lines
1.3 KiB
Rust
use bevy_math::{Mat4, Vec4};
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/// A distance calculator for the draw order of [`PhaseItem`](crate::render_phase::PhaseItem)s.
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pub struct ViewRangefinder3d {
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inverse_view_row_2: Vec4,
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}
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impl ViewRangefinder3d {
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/// Creates a 3D rangefinder for a view matrix
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pub fn from_view_matrix(view_matrix: &Mat4) -> ViewRangefinder3d {
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let inverse_view_matrix = view_matrix.inverse();
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ViewRangefinder3d {
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inverse_view_row_2: inverse_view_matrix.row(2),
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}
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}
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/// Calculates the distance, or view-space `Z` value, for a transform
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#[inline]
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pub fn distance(&self, transform: &Mat4) -> f32 {
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// NOTE: row 2 of the inverse view matrix dotted with column 3 of the model matrix
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// gives the z component of translation of the mesh in view-space
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self.inverse_view_row_2.dot(transform.col(3))
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}
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}
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#[cfg(test)]
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mod tests {
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use super::ViewRangefinder3d;
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use bevy_math::{Mat4, Vec3};
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#[test]
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fn distance() {
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let view_matrix = Mat4::from_translation(Vec3::new(0.0, 0.0, -1.0));
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let rangefinder = ViewRangefinder3d::from_view_matrix(&view_matrix);
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assert_eq!(rangefinder.distance(&Mat4::IDENTITY), 1.0);
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assert_eq!(
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rangefinder.distance(&Mat4::from_translation(Vec3::new(0.0, 0.0, 1.0))),
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2.0
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);
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}
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}
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