From 470a31dbcc9281208f259fea2407ffe7a07c8f62 Mon Sep 17 00:00:00 2001
From: Andrey Kuzmin <unsoundscapes@gmail.com>
Date: Sat, 2 Jan 2021 15:03:59 +0100
Subject: [PATCH] Implement Axis3d.intersectionWithRectangle

---
 src/Axis3d.elm          | 45 ++++++++++++++++++++++++++++---
 tests/Geometry/Fuzz.elm | 12 +++++++--
 tests/Tests/Axis3d.elm  | 60 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 112 insertions(+), 5 deletions(-)

diff --git a/src/Axis3d.elm b/src/Axis3d.elm
index 01368d9a..1b3a1640 100644
--- a/src/Axis3d.elm
+++ b/src/Axis3d.elm
@@ -12,7 +12,7 @@ module Axis3d exposing
     , x, y, z
     , through, withDirection, throughPoints, on
     , originPoint, direction
-    , intersectionWithPlane, intersectionWithSphere
+    , intersectionWithPlane, intersectionWithRectangle, intersectionWithSphere
     , reverse, moveTo, rotateAround, translateBy, translateIn, mirrorAcross, projectOnto
     , at, at_
     , relativeTo, placeIn, projectInto
@@ -46,7 +46,7 @@ by an origin point and direction. Axes have several uses, such as:
 
 # Intersection
 
-@docs intersectionWithPlane, intersectionWithSphere
+@docs intersectionWithPlane, intersectionWithRectangle, intersectionWithSphere
 
 
 # Transformations
@@ -68,9 +68,10 @@ by an origin point and direction. Axes have several uses, such as:
 import Angle exposing (Angle)
 import Axis2d exposing (Axis2d)
 import Direction3d exposing (Direction3d)
-import Geometry.Types as Types exposing (Frame3d, Plane3d, SketchPlane3d, Sphere3d, Triangle3d)
+import Geometry.Types as Types exposing (Frame3d, LineSegment3d, Plane3d, Rectangle3d, SketchPlane3d, Sphere3d, Triangle3d)
 import Point3d exposing (Point3d)
 import Quantity exposing (Quantity(..), Rate)
+import Unsafe.Direction3d as Direction3d
 import Vector3d exposing (Vector3d)
 
 
@@ -308,6 +309,44 @@ intersectionWithTriangle triangle axis =
                     |> Just
 
 
+{-| Try to find the unique intersection point of an axis with a rectangle. If
+the axis does not intersect the rectangle, or if it is coplanar with it (lying
+perfectly in the plane of the rectangle), returns `Nothing`.
+-}
+intersectionWithRectangle : Rectangle3d units coordinates -> Axis3d units coordinates -> Maybe (Point3d units coordinates)
+intersectionWithRectangle (Types.Rectangle3d { axes, dimensions }) axis =
+    let
+        (Types.SketchPlane3d sketchPlane) =
+            axes
+
+        plane =
+            Types.Plane3d
+                { normalDirection =
+                    Direction3d.unsafeCrossProduct
+                        sketchPlane.xDirection
+                        sketchPlane.yDirection
+                , originPoint = sketchPlane.originPoint
+                }
+    in
+    case intersectionWithPlane plane axis of
+        (Just point) as result ->
+            let
+                ( Quantity width, Quantity height ) =
+                    dimensions
+
+                (Types.Point2d p) =
+                    Point3d.projectInto (Types.SketchPlane3d sketchPlane) point
+            in
+            if abs p.x / width <= 0.5 && abs p.y / height <= 0.5 then
+                result
+
+            else
+                Nothing
+
+        Nothing ->
+            Nothing
+
+
 {-| Attempt to find the intersection of an axis with a sphere. The two points
 will be in order of signed distance along the axis. Returns `Nothing` if there
 is no intersection.
diff --git a/tests/Geometry/Fuzz.elm b/tests/Geometry/Fuzz.elm
index 9522f780..0e87c69e 100644
--- a/tests/Geometry/Fuzz.elm
+++ b/tests/Geometry/Fuzz.elm
@@ -3,7 +3,7 @@ module Geometry.Fuzz exposing
     , length, positiveLength, angle, quantityRange
     , point2d, point3d, vector2d, vector3d, direction2d, direction3d, boundingBox2d, boundingBox3d
     , axis2d, axis3d, frame2d, frame3d, plane3d, sketchPlane3d
-    , lineSegment2d, lineSegment3d, triangle2d, triangle3d, rectangle2d, block3d, polyline2d, polyline3d, polygon2d
+    , lineSegment2d, lineSegment3d, triangle2d, triangle3d, rectangle2d, rectangle3d, block3d, polyline2d, polyline3d, polygon2d
     , arc2d, arc3d, circle2d, circle3d, cubicSpline2d, cubicSpline3d, cylinder3d, cone3d, ellipse2d, ellipticalArc2d, ellipticalArc3d, ellipsoid3d, quadraticSpline2d, quadraticSpline3d, rationalCubicSpline2d, rationalCubicSpline3d, rationalQuadraticSpline2d, rationalQuadraticSpline3d, sphere3d
     )
 
@@ -47,7 +47,7 @@ running into any naming conflicts.
 
 # Simple geometry
 
-@docs lineSegment2d, lineSegment3d, triangle2d, triangle3d, rectangle2d, block3d, polyline2d, polyline3d, polygon2d
+@docs lineSegment2d, lineSegment3d, triangle2d, triangle3d, rectangle2d, rectangle3d, block3d, polyline2d, polyline3d, polygon2d
 
 
 # Complex geometry
@@ -97,6 +97,7 @@ import RationalCubicSpline3d exposing (RationalCubicSpline3d)
 import RationalQuadraticSpline2d exposing (RationalQuadraticSpline2d)
 import RationalQuadraticSpline3d exposing (RationalQuadraticSpline3d)
 import Rectangle2d exposing (Rectangle2d)
+import Rectangle3d exposing (Rectangle3d)
 import Shrink
 import SketchPlane3d exposing (SketchPlane3d)
 import Sphere3d exposing (Sphere3d)
@@ -571,6 +572,13 @@ rectangle2d =
     Fuzz.map3 rectangle frame2d positiveLength positiveLength
 
 
+{-| Generate a random `Rectangle3d`.
+-}
+rectangle3d : Fuzzer (Rectangle3d Meters coordinates)
+rectangle3d =
+    Fuzz.map2 Rectangle3d.on sketchPlane3d rectangle2d
+
+
 {-| Generate a random `Block3d`.
 -}
 block3d : Fuzzer (Block3d Meters coordinates)
diff --git a/tests/Tests/Axis3d.elm b/tests/Tests/Axis3d.elm
index 91cb26f8..f860dc01 100644
--- a/tests/Tests/Axis3d.elm
+++ b/tests/Tests/Axis3d.elm
@@ -1,6 +1,7 @@
 module Tests.Axis3d exposing
     ( directionExample
     , intersectionWithPlane
+    , intersectionWithRectangle
     , intersectionWithSphere
     , intersectionWithTriangle
     , onExamples
@@ -26,6 +27,8 @@ import Plane3d
 import Point2d
 import Point3d
 import Quantity
+import Rectangle2d exposing (Rectangle2d)
+import Rectangle3d
 import SketchPlane3d
 import Sphere3d
 import Test exposing (Test)
@@ -205,6 +208,63 @@ intersectionWithTriangle =
         )
 
 
+intersectionWithRectangle : Test
+intersectionWithRectangle =
+    Test.fuzz3
+        Fuzz.rectangle3d
+        Fuzz.direction3d
+        (ElmFuzz.tuple3
+            ( ElmFuzz.floatRange -0.5 1.5
+            , ElmFuzz.floatRange -0.5 1.5
+            , ElmFuzz.floatRange -10 10
+            )
+        )
+        "intersectionWithRectangle works properly"
+        (\rectangle axisDirection parameters ->
+            let
+                s =
+                    Rectangle3d.axes rectangle
+                        |> SketchPlane3d.normalDirection
+                        |> Direction3d.componentIn axisDirection
+            in
+            if abs s < 1.0e-3 then
+                Expect.pass
+
+            else
+                let
+                    ( u, v, t ) =
+                        parameters
+
+                    planeIntersection =
+                        Rectangle3d.interpolate rectangle u v
+
+                    direction =
+                        Vector3d.withLength (Length.meters 1) axisDirection
+
+                    axisOrigin =
+                        planeIntersection
+                            |> Point3d.translateBy (Vector3d.scaleBy -t direction)
+
+                    axis =
+                        Axis3d.through axisOrigin axisDirection
+                in
+                case Axis3d.intersectionWithRectangle rectangle axis of
+                    Nothing ->
+                        if u < 0 || v < 0 || u > 1 || v > 1 then
+                            Expect.pass
+
+                        else
+                            Expect.fail "Expected an intersection"
+
+                    Just point ->
+                        if u < 0 || v < 0 || u > 1 || v > 1 then
+                            Expect.fail "Expected no intersection"
+
+                        else
+                            Expect.point3d planeIntersection point
+        )
+
+
 intersectionWithSphere : Test
 intersectionWithSphere =
     Test.describe "intersectionWithSphere"