From 4a1b47174296c69e082e51935cb0b70888e65804 Mon Sep 17 00:00:00 2001
From: Fraser Graham <frasergraham@me.com>
Date: Tue, 26 Nov 2013 21:40:32 -0800
Subject: [PATCH] convenience functions for converting things to polygons

---
 govector_test.go |  5 +++++
 vectorpoint.go   | 31 ++++++++++++++++++++++++++++---
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/govector_test.go b/govector_test.go
index 0540936..d135a82 100644
--- a/govector_test.go
+++ b/govector_test.go
@@ -354,3 +354,8 @@ func TestPolyPolyIntersectFail(t *testing.T) {
 	i, m, p := PolyPolyIntersection(p1, Vector2d{0, 0}, p2)
 	fmt.Printf("%v %v %v\n", i, m, p)
 }
+
+func TestOrientedSquare(t *testing.T) {
+	p := OrientedSquare(Point2d{10, 10}, Vector2d{0.5, 0.5}, 5)
+	fmt.Printf("Square: %v\n", p)
+}
diff --git a/vectorpoint.go b/vectorpoint.go
index 2350c0e..92b54e0 100644
--- a/vectorpoint.go
+++ b/vectorpoint.go
@@ -79,6 +79,10 @@ func (p Point2d) ToVector() Vector2d {
 	return Vector2d{p.X, p.Y}
 }
 
+func (v Vector2d) ToPoint() Point2d {
+	return Point2d{v.X, v.Y}
+}
+
 func (v1 Vector2d) Rotate(a float32) Vector2d {
 	x := float64(v1.X)*math.Cos(float64(a)) - float64(v1.Y)*math.Sin(float64(a))
 	y := float64(v1.X)*math.Sin(float64(a)) + float64(v1.Y)*math.Cos(float64(a))
@@ -95,9 +99,30 @@ func RectFromPoint(p Point2d, size float32) AABB2d {
 		B: Point2d{X: p.X + size, Y: p.Y + size}}
 }
 
-func PolygonFromAABB(r AABB2d) Polygon2d {
-	// TBD
-	return Polygon2d{}
+func (r AABB2d) ToPolygon() Polygon2d {
+	p := Polygon2d{}
+
+	p.Origin = r.A
+	p.Points = append(p.Points, r.A.Sub(p.Origin))
+	p.Points = append(p.Points, Point2d{r.A.X, r.B.Y}.Sub(p.Origin))
+	p.Points = append(p.Points, r.B.Sub(p.Origin))
+	p.Points = append(p.Points, Point2d{r.B.X, r.A.Y}.Sub(p.Origin))
+
+	return p
+}
+
+func OrientedSquare(center Point2d, heading Vector2d, size float32) Polygon2d {
+	out := Polygon2d{}
+	out.Origin.X = center.X
+	out.Origin.Y = center.Y
+	x := heading.Normalize().Scale(size)
+	y := Vector2d{-x.Y, x.X}
+	z := Point2d{}
+	out.Points = append(out.Points, z.Add(x).Add(y).ToVector())
+	out.Points = append(out.Points, z.Add(y).Sub(x.ToPoint()))
+	out.Points = append(out.Points, z.Sub(x.ToPoint()).ToPoint().Sub(y.ToPoint()))
+	out.Points = append(out.Points, z.Add(x).Sub(y.ToPoint()))
+	return out
 }
 
 func (v Vector2d) Normalize() Vector2d {