From 4c6d061455e299aa3ff116c7888ab3860d9aa489 Mon Sep 17 00:00:00 2001
From: Ben Cragg <bcvery1@gmail.com>
Date: Tue, 29 Jan 2019 11:20:21 +0000
Subject: [PATCH] added rect-circle intersection functions
---
geometry.go | 32 ++++++++++++++++++++++
geometry_test.go | 70 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 102 insertions(+)
diff --git a/geometry.go b/geometry.go
index 55fbf53..b19e902 100644
--- a/geometry.go
+++ b/geometry.go
@@ -318,6 +318,16 @@ func (r Rect) Intersect(s Rect) Rect {
return t
}
+// IntersectsCircle returns whether the Circle and the Rect intersect.
+//
+// This function will return true if:
+// - The Rect contains the Circle, partially or fully
+// - The Circle contains the Rect, partially of fully
+// - An edge of the Rect is a tangent to the Circle
+func (r Rect) IntersectsCircle(c Circle) bool {
+ return c.IntersectsRect(r)
+}
+
// Circle is a 2D circle. It is defined by two properties:
// - Radius float64
// - Center vector
@@ -470,6 +480,28 @@ func (c Circle) Intersect(d Circle) Circle {
}
}
+// IntersectsRect returns whether the Circle and the Rect intersect.
+//
+// This function will return true if:
+// - The Rect contains the Circle, partially or fully
+// - The Circle contains the Rect, partially of fully
+// - An edge of the Rect is a tangent to the Circle
+func (c Circle) IntersectsRect(r Rect) bool {
+ // Checks if the c.Center is not in the diagonal quadrants of the rectangle
+ var grownR Rect
+ if (r.Min.X <= c.Center.X && c.Center.X <= r.Max.X) || (r.Min.Y <= c.Center.Y && c.Center.Y <= r.Max.Y) {
+ // 'grow' the Rect by c.Radius in each diagonal
+ grownR = Rect{
+ Min: r.Min.Sub(V(c.Radius, c.Radius)),
+ Max: r.Max.Add(V(c.Radius, c.Radius)),
+ }
+
+ return grownR.Contains(c.Center)
+ }
+ // The center is in the diagonal quadrants
+ return c.Center.To(r.Min).Len() <= c.Radius || c.Center.To(r.Max).Len() <= c.Radius
+}
+
// Matrix is a 2x3 affine matrix that can be used for all kinds of spatial transforms, such
// as movement, scaling and rotations.
//
diff --git a/geometry_test.go b/geometry_test.go
index cda1dc6..a3aa5f8 100644
--- a/geometry_test.go
+++ b/geometry_test.go
@@ -576,3 +576,73 @@ func TestCircle_Intersect(t *testing.T) {
})
}
}
+
+func TestRect_IntersectsCircle(t *testing.T) {
+ type fields struct {
+ Min pixel.Vec
+ Max pixel.Vec
+ }
+ type args struct {
+ c pixel.Circle
+ }
+ tests := []struct {
+ name string
+ fields fields
+ args args
+ want bool
+ }{
+ {
+ name: "Rect.IntersectsCircle(): no overlap",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(1, pixel.V(50, 50))},
+ want: false,
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle contains rect",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(10, pixel.V(5, 5))},
+ want: true,
+ },
+ {
+ name: "Rect.IntersectsCircle(): rect contains circle",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(1, pixel.V(5, 5))},
+ want: true,
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps one corner",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(1, pixel.V(0, 0))},
+ want: true,
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps two corner",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(11, pixel.V(0, 5))},
+ want: true,
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps one edge",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(1, pixel.V(0, 5))},
+ want: true,
+ },
+ {
+ name: "Rect.IntersectsCircle(): edge is tangent",
+ fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(1, pixel.V(-1, 5))},
+ want: true,
+ },
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ r := pixel.Rect{
+ Min: tt.fields.Min,
+ Max: tt.fields.Max,
+ }
+ if got := r.IntersectsCircle(tt.args.c); got != tt.want {
+ t.Errorf("Rect.IntersectsCircle() = %v, want %v", got, tt.want)
+ }
+ })
+ }
+}
--
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