diff --git a/geometry.go b/geometry.go
index 7353f1af389f360a63f2fa1e98a38265723c0ea7..593736100c958df20e1329e3cffef62836f550a8 100644
--- a/geometry.go
+++ b/geometry.go
@@ -310,14 +310,15 @@ func (r Rect) Intersect(s Rect) Rect {
return t
}
-// IntersectsCircle returns whether the Circle and the Rect intersect.
+// IntersectsCircle returns a minimal required Vector, such that moving the circle by that vector would stop the Circle
+// and the Rect intersecting. This function returns a zero-vector if the Circle and Rect do not overlap, and if only
+// the perimeters touch.
//
// 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)
+func (r Rect) IntersectsCircle(c Circle) Vec {
+ return c.IntersectsRect(r).Scaled(-1)
}
// Circle is a 2D circle. It is defined by two properties:
@@ -467,24 +468,79 @@ func (c Circle) Intersect(d Circle) Circle {
}
}
-// IntersectsRect returns whether the Circle and the Rect intersect.
+// IntersectsRect returns a minimal required Vector, such that moving the circle by that vector would stop the Circle
+// and the Rect intersecting. This function returns a zero-vector if the Circle and Rect do not overlap, and if only
+// the perimeters touch.
//
// 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 {
+func (c Circle) IntersectsRect(r Rect) Vec {
+ // h and v will hold the minimum horizontal and vertical distances (respectively) to avoid overlapping
+ var h, v float64
+
// Checks if the c.Center is not in the diagonal quadrants of the rectangle
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 orthagonal
- return Rect{
- Min: r.Min.Sub(V(c.Radius, c.Radius)),
- Max: r.Max.Add(V(c.Radius, c.Radius)),
- }.Contains(c.Center)
+ grown := Rect{Min: r.Min.Sub(V(c.Radius, c.Radius)), Max: r.Max.Add(V(c.Radius, c.Radius))}
+ if !grown.Contains(c.Center) {
+ // c.Center not close enough to overlap, return zero-vector
+ return ZV
+ }
+
+ // Get minimum distance to travel out of Rect
+ rToC := r.Center().To(c.Center)
+ h = c.Radius - math.Abs(rToC.X) + (r.W() / 2)
+ v = c.Radius - math.Abs(rToC.Y) + (r.H() / 2)
+
+ if rToC.X < 0 {
+ h = -h
+ }
+ if rToC.Y < 0 {
+ v = -v
+ }
+ } else {
+ // The center is in the diagonal quadrants
+ if c.Center.To(r.Min).Len() <= c.Radius {
+ // Closest to bottom-left
+ cornerToCenter := r.Min.To(c.Center)
+ // Get the horizontal and vertical overlaps
+ h = c.Radius - math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.Y, 2))
+ v = -1 * (c.Radius + math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.X, 2)))
+ }
+ if c.Center.To(r.Max).Len() <= c.Radius {
+ // Closest to top-right
+ cornerToCenter := r.Max.To(c.Center)
+ // Get the horizontal and vertical overlaps
+ h = c.Radius - math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.Y, 2))
+ v = c.Radius - math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.X, 2))
+ }
+ if c.Center.To(V(r.Min.X, r.Max.Y)).Len() <= c.Radius {
+ // Closest to top-left
+ cornerToCenter := V(r.Min.X, r.Max.Y).To(c.Center)
+ // Get the horizontal and vertical overlaps
+ h = -1 * (c.Radius + math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.Y, 2)))
+ v = c.Radius - math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.X, 2))
+ }
+ if c.Center.To(V(r.Max.X, r.Min.Y)).Len() <= c.Radius {
+ // Closest to bottom-right
+ cornerToCenter := V(r.Max.X, r.Min.Y).To(c.Center)
+ // Get the horizontal and vertical overlaps
+ h = -1 * (c.Radius + math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.Y, 2)))
+ v = -1 * (c.Radius + math.Sqrt(math.Pow(c.Radius, 2)-math.Pow(cornerToCenter.X, 2)))
+ }
+ }
+
+ // No intersect
+ if h == 0 && v == 0 {
+ return ZV
+ }
+
+ if math.Abs(h) > math.Abs(v) {
+ // Vertical distance shorter
+ return V(0, v)
}
- // The center is in the diagonal quadrants
- return c.Center.To(r.Min).Len() <= c.Radius || c.Center.To(r.Max).Len() <= c.Radius ||
- c.Center.To(V(r.Min.X, r.Max.Y)).Len() <= c.Radius || c.Center.To(V(r.Max.X, r.Min.Y)).Len() <= c.Radius
+ return V(h, 0)
}
// Matrix is a 2x3 affine matrix that can be used for all kinds of spatial transforms, such
diff --git a/geometry_test.go b/geometry_test.go
index eec854de9fb4776d0f6b8b1c8a4a1d23644302c6..2bdc2840985dfe79ab3fc2b53c05c6e0d1b8ee1d 100644
--- a/geometry_test.go
+++ b/geometry_test.go
@@ -469,55 +469,85 @@ func TestRect_IntersectsCircle(t *testing.T) {
name string
fields fields
args args
- want bool
+ want pixel.Vec
}{
{
name: "Rect.IntersectsCircle(): no overlap",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(50, 50), 1)},
- want: false,
+ want: pixel.ZV,
},
{
name: "Rect.IntersectsCircle(): circle contains rect",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(5, 5), 10)},
- want: true,
+ want: pixel.V(-15, 0),
},
{
name: "Rect.IntersectsCircle(): rect contains circle",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(5, 5), 1)},
- want: true,
+ want: pixel.V(-6, 0),
},
{
name: "Rect.IntersectsCircle(): circle overlaps bottom-left corner",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
- args: args{c: pixel.C(pixel.V(-.5, -.5), 1)},
- want: true,
+ args: args{c: pixel.C(pixel.V(0, 0), 1)},
+ want: pixel.V(1, 0),
},
{
name: "Rect.IntersectsCircle(): circle overlaps top-left corner",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
- args: args{c: pixel.C(pixel.V(-.5, 10.5), 1)},
- want: true,
+ args: args{c: pixel.C(pixel.V(0, 10), 1)},
+ want: pixel.V(1, 0),
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps bottom-right corner",
+ fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(pixel.V(10, 0), 1)},
+ want: pixel.V(-1, 0),
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps top-right corner",
+ fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(pixel.V(10, 10), 1)},
+ want: pixel.V(-1, 0),
},
{
name: "Rect.IntersectsCircle(): circle overlaps two corners",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(0, 5), 6)},
- want: true,
+ want: pixel.V(6, 0),
},
{
- name: "Rect.IntersectsCircle(): circle overlaps one edge",
+ name: "Rect.IntersectsCircle(): circle overlaps left edge",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(0, 5), 1)},
- want: true,
+ want: pixel.V(1, 0),
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps bottom edge",
+ fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(pixel.V(5, 0), 1)},
+ want: pixel.V(0, 1),
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps right edge",
+ fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(pixel.V(10, 5), 1)},
+ want: pixel.V(-1, 0),
+ },
+ {
+ name: "Rect.IntersectsCircle(): circle overlaps top edge",
+ fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+ args: args{c: pixel.C(pixel.V(5, 10), 1)},
+ want: pixel.V(0, -1),
},
{
name: "Rect.IntersectsCircle(): edge is tangent",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(-1, 5), 1)},
- want: true,
+ want: pixel.ZV,
},
}
for _, tt := range tests {