From 58329a83f6bfc652e36514655a49e9b28c4df587 Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Thu, 13 Oct 2022 14:19:17 +0200
Subject: [PATCH 1/5] Add dependency on `robust-predicates` to `fj-math`

---
 Cargo.lock                | 1 +
 crates/fj-math/Cargo.toml | 1 +
 2 files changed, 2 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 823d90e79..d94f38b01 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1026,6 +1026,7 @@ dependencies = [
  "num-traits",
  "parry2d-f64",
  "parry3d-f64",
+ "robust-predicates",
 ]
 
 [[package]]
diff --git a/crates/fj-math/Cargo.toml b/crates/fj-math/Cargo.toml
index 73342ea30..6aeed7f46 100644
--- a/crates/fj-math/Cargo.toml
+++ b/crates/fj-math/Cargo.toml
@@ -17,3 +17,4 @@ nalgebra = "0.31.2"
 num-traits = "0.2.15"
 parry2d-f64 = "0.10.0"
 parry3d-f64 = "0.10.0"
+robust-predicates = "0.1.3"

From cd1844fc4f735e51ea5477dd6b94fd0b9cb3a9ae Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Thu, 13 Oct 2022 14:20:29 +0200
Subject: [PATCH 2/5] Fix `Triangle<2>::winding_direction`

For some reason, the Parry function gave a wrong result.
---
 crates/fj-math/src/triangle.rs | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/crates/fj-math/src/triangle.rs b/crates/fj-math/src/triangle.rs
index cbafd436e..2c3cffb32 100644
--- a/crates/fj-math/src/triangle.rs
+++ b/crates/fj-math/src/triangle.rs
@@ -1,4 +1,4 @@
-use parry2d_f64::utils::point_in_triangle::{corner_direction, Orientation};
+use parry2d_f64::utils::point_in_triangle::Orientation;
 use parry3d_f64::query::{Ray, RayCast as _};
 
 use crate::Vector;
@@ -59,8 +59,17 @@ impl<const D: usize> Triangle<D> {
 impl Triangle<2> {
     /// Returns the direction of the line through the points of the triangle.
     pub fn winding_direction(&self) -> Winding {
-        let [v0, v1, v2] = self.points.map(|point| point.to_na());
-        corner_direction(&v0, &v1, &v2).into()
+        let [pa, pb, pc] = self.points.map(|point| point.into());
+        let orient2d = robust_predicates::orient2d(&pa, &pb, &pc);
+
+        if orient2d < 0. {
+            return Winding::Cw;
+        }
+        if orient2d > 0. {
+            return Winding::Ccw;
+        }
+
+        unreachable!("not a triangle")
     }
 }
 

From fdd53a88aab7c19bdb8287f4d2c7ca4d75057d9d Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Thu, 13 Oct 2022 14:21:27 +0200
Subject: [PATCH 3/5] Simplify method name

---
 crates/fj-kernel/src/algorithms/triangulate/delaunay.rs | 2 +-
 crates/fj-math/src/triangle.rs                          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/crates/fj-kernel/src/algorithms/triangulate/delaunay.rs b/crates/fj-kernel/src/algorithms/triangulate/delaunay.rs
index bc45a4dee..bc1fcad1f 100644
--- a/crates/fj-kernel/src/algorithms/triangulate/delaunay.rs
+++ b/crates/fj-kernel/src/algorithms/triangulate/delaunay.rs
@@ -22,7 +22,7 @@ pub fn triangulate(
             v2.point_surface,
         ])
         .expect("invalid triangle")
-        .winding_direction();
+        .winding();
 
         let required_winding = match coord_handedness {
             Handedness::LeftHanded => Winding::Cw,
diff --git a/crates/fj-math/src/triangle.rs b/crates/fj-math/src/triangle.rs
index 2c3cffb32..78f9836f4 100644
--- a/crates/fj-math/src/triangle.rs
+++ b/crates/fj-math/src/triangle.rs
@@ -58,7 +58,7 @@ impl<const D: usize> Triangle<D> {
 
 impl Triangle<2> {
     /// Returns the direction of the line through the points of the triangle.
-    pub fn winding_direction(&self) -> Winding {
+    pub fn winding(&self) -> Winding {
         let [pa, pb, pc] = self.points.map(|point| point.into());
         let orient2d = robust_predicates::orient2d(&pa, &pb, &pc);
 

From cc7936b29b38033596c48a38f73b7963b704c677 Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Thu, 13 Oct 2022 14:22:19 +0200
Subject: [PATCH 4/5] Improve panic message

---
 crates/fj-math/src/triangle.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/crates/fj-math/src/triangle.rs b/crates/fj-math/src/triangle.rs
index 78f9836f4..54504870e 100644
--- a/crates/fj-math/src/triangle.rs
+++ b/crates/fj-math/src/triangle.rs
@@ -69,7 +69,10 @@ impl Triangle<2> {
             return Winding::Ccw;
         }
 
-        unreachable!("not a triangle")
+        unreachable!(
+            "Points don't form a triangle, but this was verified in the \
+            constructor."
+        )
     }
 }
 

From 670a155386eff18e9c88b9c8d739d5ace6d81460 Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Thu, 13 Oct 2022 14:23:49 +0200
Subject: [PATCH 5/5] Remove unused code

---
 crates/fj-math/src/triangle.rs | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/crates/fj-math/src/triangle.rs b/crates/fj-math/src/triangle.rs
index 54504870e..fb763017f 100644
--- a/crates/fj-math/src/triangle.rs
+++ b/crates/fj-math/src/triangle.rs
@@ -1,4 +1,3 @@
-use parry2d_f64::utils::point_in_triangle::Orientation;
 use parry3d_f64::query::{Ray, RayCast as _};
 
 use crate::Vector;
@@ -134,16 +133,6 @@ pub enum Winding {
     Cw,
 }
 
-impl From<Orientation> for Winding {
-    fn from(o: Orientation) -> Self {
-        match o {
-            Orientation::Ccw => Winding::Ccw,
-            Orientation::Cw => Winding::Cw,
-            Orientation::None => unreachable!("not a triangle"),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use crate::{Point, Vector};