From 885832d5b214d3ce16d532c6d35ceb30387a5589 Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Fri, 23 Feb 2024 12:53:24 +0100
Subject: [PATCH] Remove unused surface/surface intersection code

---
 .../fj-core/src/algorithms/intersect/mod.rs   |   2 -
 .../algorithms/intersect/surface_surface.rs   | 113 ------------------
 2 files changed, 115 deletions(-)
 delete mode 100644 crates/fj-core/src/algorithms/intersect/surface_surface.rs

diff --git a/crates/fj-core/src/algorithms/intersect/mod.rs b/crates/fj-core/src/algorithms/intersect/mod.rs
index 58acf0d8e..8a841efaa 100644
--- a/crates/fj-core/src/algorithms/intersect/mod.rs
+++ b/crates/fj-core/src/algorithms/intersect/mod.rs
@@ -7,7 +7,6 @@ pub mod ray_segment;
 mod curve_edge;
 mod curve_face;
 mod line_segment;
-mod surface_surface;
 
 use fj_math::{Point, Vector};
 
@@ -15,7 +14,6 @@ pub use self::{
     curve_edge::CurveEdgeIntersection,
     curve_face::{CurveFaceIntersection, CurveFaceIntersectionInterval},
     line_segment::LineSegmentIntersection,
-    surface_surface::SurfaceSurfaceIntersection,
 };
 
 /// Compute the intersection between a tuple of objects
diff --git a/crates/fj-core/src/algorithms/intersect/surface_surface.rs b/crates/fj-core/src/algorithms/intersect/surface_surface.rs
deleted file mode 100644
index a5be37894..000000000
--- a/crates/fj-core/src/algorithms/intersect/surface_surface.rs
+++ /dev/null
@@ -1,113 +0,0 @@
-use fj_math::{Line, Plane, Point, Scalar};
-
-use crate::{
-    geometry::{GlobalPath, SurfacePath},
-    objects::Surface,
-    storage::Handle,
-};
-
-/// The intersection between two surfaces
-#[derive(Clone, Debug, Eq, PartialEq, Hash, Ord, PartialOrd)]
-pub struct SurfaceSurfaceIntersection {
-    /// The intersection curves
-    pub intersection_curves: [SurfacePath; 2],
-}
-
-impl SurfaceSurfaceIntersection {
-    /// Compute the intersection between two surfaces
-    pub fn compute(surfaces: [Handle<Surface>; 2]) -> Option<Self> {
-        // Algorithm from Real-Time Collision Detection by Christer Ericson. See
-        // section 5.4.4, Intersection of Two Planes.
-        //
-        // Adaptations were made to get the intersection curves in local
-        // coordinates for each surface.
-
-        let planes = surfaces.map(|surface| plane_from_surface(&surface));
-
-        let [(a_distance, a_normal), (b_distance, b_normal)] =
-            planes.map(|plane| plane.constant_normal_form());
-
-        let direction = a_normal.cross(&b_normal);
-
-        let denom = direction.dot(&direction);
-        if denom == Scalar::ZERO {
-            // Comparing `denom` against zero looks fishy. It's probably better
-            // to compare it against an epsilon value, but I don't know how
-            // large that epsilon should be.
-            //
-            // I'll just leave it like that, until we had the opportunity to
-            // collect some experience with this code.
-            // - @hannobraun
-            return None;
-        }
-
-        let origin = (b_normal * a_distance - a_normal * b_distance)
-            .cross(&direction)
-            / denom;
-        let origin = Point { coords: origin };
-
-        let line = Line::from_origin_and_direction(origin, direction);
-
-        let curves =
-            planes.map(|plane| SurfacePath::Line(plane.project_line(&line)));
-
-        Some(Self {
-            intersection_curves: curves,
-        })
-    }
-}
-
-fn plane_from_surface(surface: &Surface) -> Plane {
-    let (line, path) = {
-        let line = match surface.geometry().u {
-            GlobalPath::Line(line) => line,
-            _ => todo!("Only plane-plane intersection is currently supported."),
-        };
-
-        (line, surface.geometry().v)
-    };
-
-    Plane::from_parametric(line.origin(), line.direction(), path)
-}
-
-#[cfg(test)]
-mod tests {
-    use fj_math::Transform;
-    use pretty_assertions::assert_eq;
-
-    use crate::{
-        geometry::SurfacePath, operations::transform::TransformObject, Core,
-    };
-
-    use super::SurfaceSurfaceIntersection;
-
-    #[test]
-    fn plane_plane() {
-        let mut core = Core::new();
-
-        let xy = core.layers.objects.surfaces.xy_plane();
-        let xz = core.layers.objects.surfaces.xz_plane();
-
-        // Coincident and parallel planes don't have an intersection curve.
-        assert_eq!(
-            SurfaceSurfaceIntersection::compute([
-                xy.clone(),
-                xy.clone().transform(
-                    &Transform::translation([0., 0., 1.],),
-                    &mut core
-                )
-            ],),
-            None,
-        );
-
-        let expected_xy = SurfacePath::u_axis();
-        let expected_xz = SurfacePath::u_axis();
-
-        assert_eq!(
-            SurfaceSurfaceIntersection::compute([xy, xz],),
-            Some(SurfaceSurfaceIntersection {
-                intersection_curves: [expected_xy, expected_xz],
-            })
-        );
-    }
-}