vector/vectorpoint.go

package govector

import (
	"math"
)

type Rect2d struct {
	X1 float64 `json:"x1"`
	Y1 float64 `json:"y1"`
	X2 float64 `json:"x2"`
	Y2 float64 `json:"y2"`
}

type Vector2d struct {
	X float64 `json:"x"`
	Y float64 `json:"y"`
}

type Point2d struct {
	X float64 `json:"x"`
	Y float64 `json:"y"`
}

const epsilon = 1e-7
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}
}

func (p Point2d) Add(v Vector2d) Point2d {
	return Point2d{p.X + v.X, p.Y + v.Y}
}

func (v Vector2d) Mag() float64 {
	return math.Abs(math.Sqrt(v.X*v.X + v.Y*v.Y))
}

func (v Vector2d) PopPop() float64 {
	return v.Mag()
}

func (v Vector2d) Scale(s float64) Vector2d {
	return Vector2d{v.X * s, v.Y * s}
}

func (v1 Vector2d) Cross(v2 Vector2d) float64 {
	return v1.X*v2.Y - v1.Y*v2.X
}

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)
	if t >= 0 && t <= 1 && s >= 0 && s <= 1 {
		return true, p1.Add(v1.Scale(t))
	}

	return false, Point2d{0, 0}
}

func (v Vector2d) Normalize() Vector2d {
	if v.X == 0 && v.Y == 0 {
		return v
	}

	m := v.Mag()
	return Vector2d{v.X / m, v.Y / m}
}

func Move(d1, d2 Point2d, velocity float64, timeDelta float64) Point2d {
	v := d2.Sub(d1)
	v_norm := v.Normalize()
	v_scaled := v_norm.Scale(velocity * timeDelta)
	return d1.Add(v_scaled)
}

func Distance(p1, p2 Point2d) float64 {
	return p1.Sub(p2).Mag()
}

func Angle(v1, v2 Vector2d) float64 {
	x := (v1.Dot(v2) / (v1.Mag() * v2.Mag()))
	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
}