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changes to angle computation to deal with directions

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This commit is contained in:
Fraser Graham 2013-09-21 20:00:24 -07:00
parent 70c53c6e9a
commit 3232b29939
2 changed files with 37 additions and 6 deletions
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26
govector_test.go
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@ -138,8 +138,8 @@ func TestAngle(t *testing.T) {
a := Angle(v2, v1)
fmt.Printf("%v %v %f\n", v1, v2, a*rad2deg)
if math.Abs(a-math.Pi/2) > epsilon {
fmt.Printf("%v %v %f\n", v1, v2, a*Rad2deg)
if math.Abs(a)-math.Pi/2 > epsilon {
t.Errorf("Angle Error")
}
@ -148,10 +148,28 @@ func TestAngle(t *testing.T) {
a = Angle(v1, v2)
fmt.Printf("%v %v %f\n", v1, v2, a*rad2deg)
fmt.Printf("%v %v %f\n", v1, v2, a*Rad2deg)
if math.Abs(a-math.Pi/4) > epsilon {
if math.Abs(a)-math.Pi/4 > epsilon {
t.Errorf("Angle Error")
}
}
func TestRotate(t *testing.T) {
v1 := Vector2d{10, 0}
v2 := v1.Rotate(math.Pi / 2)
fmt.Printf("%v %v\n", v1, v2)
if v2.X > epsilon || v2.Y-10 > epsilon {
t.Errorf("Rotate Error")
}
v1 = Vector2d{1, 0}
v2 = v1.Rotate(-30 * Deg2rad)
fmt.Printf("%v %v\n", v1, v2)
if v2.X-0.866025403784438 > epsilon || v2.Y+0.5 > epsilon {
t.Errorf("Rotate Error")
}
}

17
vectorpoint.go
View File

@ -22,7 +22,8 @@ type Point2d struct {
}
const epsilon = 1e-7
const rad2deg = 180 / math.Pi
const Rad2deg = 180 / math.Pi
const Deg2rad = math.Pi / 180
func (p1 Point2d) Sub(p2 Point2d) Vector2d {
return Vector2d{p1.X - p2.X, p1.Y - p2.Y}
@ -52,6 +53,12 @@ func (v1 Vector2d) Dot(v2 Vector2d) float64 {
return (v1.X * v2.X) + (v1.Y * v2.Y)
}
func (v1 Vector2d) Rotate(a float64) Vector2d {
x := v1.X*math.Cos(a) - v1.Y*math.Sin(a)
y := v1.X*math.Sin(a) + v1.Y*math.Cos(a)
return Vector2d{x, y}
}
func Intersection(p1, p2 Point2d, v1, v2 Vector2d) (bool, Point2d) {
t := p2.Sub(p1).Cross(v2) / v1.Cross(v2)
s := p2.Sub(p1).Cross(v1) / v1.Cross(v2)
@ -84,5 +91,11 @@ func Distance(p1, p2 Point2d) float64 {
func Angle(v1, v2 Vector2d) float64 {
x := (v1.Dot(v2) / (v1.Mag() * v2.Mag()))
return math.Acos(x)
angle := math.Acos(x)
// Determine the sign to see what direction
// the angle should go in
if v1.Y*v2.X > v1.X*v2.Y {
angle = angle * -1.0
}
return angle
}