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Merge pull request #162 from bcvery1/fixCircleIntersect 

Fix circle intersect
This commit is contained in:
Michal Štrba 2019-02-22 17:13:57 +01:00 committed by GitHub
parent 8563c28493 b3246f6234
commit 3cc0ec3d30
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 56 additions and 41 deletions
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65
geometry.go
View File

@ -484,9 +484,6 @@ func (c Circle) Intersect(d Circle) Circle {
// - The Rect contains the Circle, partially or fully
// - The Circle contains the Rect, partially of fully
func (c Circle) IntersectRect(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
@ -498,8 +495,8 @@ func (c Circle) IntersectRect(r Rect) Vec {
// 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)
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
@ -507,48 +504,52 @@ func (c Circle) IntersectRect(r Rect) Vec {
if rToC.Y < 0 {
v = -v
}
// No intersect
if h == 0 && v == 0 {
return ZV
}
if math.Abs(h) > math.Abs(v) {
// Vertical distance shorter
return V(0, v)
}
return V(h, 0)
} else {
// The center is in the diagonal quadrants
// Helper points to make code below easy to read.
rectTopLeft := V(r.Min.X, r.Max.Y)
rectBottomRight := V(r.Max.X, r.Min.Y)
// Check for overlap.
if !(c.Contains(r.Min) || c.Contains(r.Max) || c.Contains(rectTopLeft) || c.Contains(rectBottomRight)) {
// No overlap.
return ZV
}
var centerToCorner Vec
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)))
centerToCorner = c.Center.To(r.Min)
}
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))
centerToCorner = c.Center.To(r.Max)
}
if c.Center.To(V(r.Min.X, r.Max.Y)).Len() <= c.Radius {
if c.Center.To(rectTopLeft).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))
centerToCorner = c.Center.To(rectTopLeft)
}
if c.Center.To(V(r.Max.X, r.Min.Y)).Len() <= c.Radius {
if c.Center.To(rectBottomRight).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)))
centerToCorner = c.Center.To(rectBottomRight)
}
}
// No intersect
if h == 0 && v == 0 {
return ZV
}
cornerToCircumferenceLen := c.Radius - centerToCorner.Len()
if math.Abs(h) > math.Abs(v) {
// Vertical distance shorter
return V(0, v)
return centerToCorner.Unit().Scaled(cornerToCircumferenceLen)
}
return V(h, 0)
}
// Matrix is a 2x3 affine matrix that can be used for all kinds of spatial transforms, such

32
geometry_test.go
View File

@ -542,6 +542,19 @@ func TestCircle_Intersect(t *testing.T) {
}
func TestRect_IntersectCircle(t *testing.T) {
// closeEnough will shift the decimal point by the accuracy required, truncates the results and compares them.
// Effectively this compares two floats to a given decimal point.
// Example:
// closeEnough(100.125342432, 100.125, 2) == true
// closeEnough(math.Pi, 3.14, 2) == true
// closeEnough(0.1234, 0.1245, 3) == false
closeEnough := func(got, expected float64, decimalAccuracy int) bool {
gotShifted := got * math.Pow10(decimalAccuracy)
expectedShifted := expected * math.Pow10(decimalAccuracy)
return math.Trunc(gotShifted) == math.Trunc(expectedShifted)
}
type fields struct {
Min pixel.Vec
Max pixel.Vec
@ -576,26 +589,26 @@ func TestRect_IntersectCircle(t *testing.T) {
{
name: "Rect.IntersectCircle(): circle overlaps bottom-left corner",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(0, 0), 1)},
want: pixel.V(1, 0),
args: args{c: pixel.C(pixel.V(-0.5, -0.5), 1)},
want: pixel.V(-0.2, -0.2),
},
{
name: "Rect.IntersectCircle(): circle overlaps top-left corner",
fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
args: args{c: pixel.C(pixel.V(0, 10), 1)},
want: pixel.V(1, 0),
args: args{c: pixel.C(pixel.V(-0.5, 10.5), 1)},
want: pixel.V(-0.2, 0.2),
},
{
name: "Rect.IntersectCircle(): 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),
args: args{c: pixel.C(pixel.V(10.5, -0.5), 1)},
want: pixel.V(0.2, -0.2),
},
{
name: "Rect.IntersectCircle(): 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),
args: args{c: pixel.C(pixel.V(10.5, 10.5), 1)},
want: pixel.V(0.2, 0.2),
},
{
name: "Rect.IntersectCircle(): circle overlaps two corners",
@ -670,7 +683,8 @@ func TestRect_IntersectCircle(t *testing.T) {
Min: tt.fields.Min,
Max: tt.fields.Max,
}
if got := r.IntersectCircle(tt.args.c); got != tt.want {
got := r.IntersectCircle(tt.args.c)
if !closeEnough(got.X, tt.want.X, 2) || !closeEnough(got.Y, tt.want.Y, 2) {
t.Errorf("Rect.IntersectCircle() = %v, want %v", got, tt.want)
}
})