From bedf2fd14e102854d9f959ce8cbbc62800a5a8fd Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Fri, 16 Dec 2022 16:55:42 +0100
Subject: [PATCH] Return coords from `SurfaceBuilder` method

---
 crates/fj-kernel/src/builder/shell.rs   |  3 ++-
 crates/fj-kernel/src/builder/surface.rs | 27 ++++++++++++++++++-------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/crates/fj-kernel/src/builder/shell.rs b/crates/fj-kernel/src/builder/shell.rs
index 75bc79f49..1e2006ba5 100644
--- a/crates/fj-kernel/src/builder/shell.rs
+++ b/crates/fj-kernel/src/builder/shell.rs
@@ -67,7 +67,8 @@ impl ShellBuilder for PartialShell {
                         });
                     let c = a + [Z, Z, edge_length];
 
-                    let surface = PartialSurface::plane_from_points([a, b, c]);
+                    let (surface, _) =
+                        PartialSurface::plane_from_points([a, b, c]);
                     Partial::from_partial(surface)
                 })
                 .collect::<Vec<_>>();
diff --git a/crates/fj-kernel/src/builder/surface.rs b/crates/fj-kernel/src/builder/surface.rs
index dc0b8db40..54f1efcdd 100644
--- a/crates/fj-kernel/src/builder/surface.rs
+++ b/crates/fj-kernel/src/builder/surface.rs
@@ -1,4 +1,4 @@
-use fj_math::{Point, Vector};
+use fj_math::{Point, Scalar, Vector};
 
 use crate::{
     geometry::{path::GlobalPath, surface::SurfaceGeometry},
@@ -11,7 +11,9 @@ pub trait SurfaceBuilder: Sized {
     fn from_axes(u: GlobalPath, v: impl Into<Vector<3>>) -> Self;
 
     /// Construct a plane from 3 points
-    fn plane_from_points(points: [impl Into<Point<3>>; 3]) -> Self;
+    fn plane_from_points(
+        points: [impl Into<Point<3>>; 3],
+    ) -> (Self, [Point<2>; 3]);
 }
 
 impl SurfaceBuilder for PartialSurface {
@@ -23,14 +25,25 @@ impl SurfaceBuilder for PartialSurface {
         }
     }
 
-    fn plane_from_points(points: [impl Into<Point<3>>; 3]) -> Self {
+    fn plane_from_points(
+        points: [impl Into<Point<3>>; 3],
+    ) -> (Self, [Point<2>; 3]) {
         let [a, b, c] = points.map(Into::into);
 
-        let (u, _) = GlobalPath::line_from_points([a, b]);
+        let (u, u_coords) = GlobalPath::line_from_points([a, b]);
         let v = c - a;
 
-        Self {
-            geometry: Some(SurfaceGeometry { u, v }),
-        }
+        let coords = {
+            let [a, b] = u_coords.map(|point| point.t);
+            [[a, Scalar::ZERO], [b, Scalar::ZERO], [a, Scalar::ONE]]
+                .map(Point::from)
+        };
+
+        (
+            Self {
+                geometry: Some(SurfaceGeometry { u, v }),
+            },
+            coords,
+        )
     }
 }