From acd13fd925c7fad76af9339657fb275ae8e3f47e Mon Sep 17 00:00:00 2001
From: Hanno Braun <hello@hannobraun.com>
Date: Thu, 9 Jan 2025 18:52:54 +0100
Subject: [PATCH] Add `Plane::project_point`

---
 experiments/2024-12-09/src/math/plane.rs | 36 ++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/experiments/2024-12-09/src/math/plane.rs b/experiments/2024-12-09/src/math/plane.rs
index 13f468c8f..98ebdc274 100644
--- a/experiments/2024-12-09/src/math/plane.rs
+++ b/experiments/2024-12-09/src/math/plane.rs
@@ -25,6 +25,22 @@ impl Plane {
         self.origin + self.coords.a * u + self.coords.b * v
     }
 
+    #[allow(unused)] // code to use it is being worked on
+    pub fn project_point(&self, point: impl Into<Point<3>>) -> Point<2> {
+        let point = point.into();
+        let origin_to_point = point - self.origin;
+
+        let min_distance_plane_to_point = origin_to_point.dot(&self.normal());
+        let point_in_plane =
+            point - self.normal() * min_distance_plane_to_point;
+        let origin_to_point_in_plane = point_in_plane - self.origin;
+
+        let u = origin_to_point_in_plane.dot(&self.u());
+        let v = origin_to_point_in_plane.dot(&self.v());
+
+        Point::from([u, v])
+    }
+
     pub fn translate(self, offset: impl Into<Vector<3>>) -> Self {
         Self {
             origin: self.origin + offset,
@@ -32,3 +48,23 @@ impl Plane {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::math::{Bivector, Point, Vector};
+
+    use super::Plane;
+
+    #[test]
+    fn project_point() {
+        let plane = Plane {
+            origin: Point::from([1., 1., 1.]),
+            coords: Bivector {
+                a: Vector::from([1., 0., 0.]),
+                b: Vector::from([0., 1., 0.]),
+            },
+        };
+
+        assert_eq!(plane.project_point([2., 2., 2.]), Point::from([1., 1.]));
+    }
+}