Golang math.Cos函数代码示例

//GridToGeodetic converts RT90 coordinates to WGS84
func GridToGeodetic(x, y float64) (float64, float64) {

	if CentralMeridian == 31337.0 {
		return 0.0, 0.0
	}

	e2 := Flattening * (2.0 - Flattening)
	n := Flattening / (2.0 - Flattening)
	a_roof := Axis / (1.0 + n) * (1.0 + n*n/4.0 + n*n*n*n/64.0)
	delta1 := n/2.0 - 2.0*n*n/3.0 + 37.0*n*n*n/96.0 - n*n*n*n/360.0
	delta2 := n*n/48.0 + n*n*n/15.0 - 437.0*n*n*n*n/1440.0
	delta3 := 17.0*n*n*n/480.0 - 37*n*n*n*n/840.0
	delta4 := 4397.0 * n * n * n * n / 161280.0

	Astar := e2 + e2*e2 + e2*e2*e2 + e2*e2*e2*e2
	Bstar := -(7.0*e2*e2 + 17.0*e2*e2*e2 + 30.0*e2*e2*e2*e2) / 6.0
	Cstar := (224.0*e2*e2*e2 + 889.0*e2*e2*e2*e2) / 120.0
	Dstar := -(4279.0 * e2 * e2 * e2 * e2) / 1260.0

	DegToRad := math.Pi / 180
	LambdaZero := CentralMeridian * DegToRad
	xi := (x - FalseNorthing) / (Scale * a_roof)
	eta := (y - FalseEasting) / (Scale * a_roof)
	xi_prim := xi - delta1*math.Sin(2.0*xi)*math.Cosh(2.0*eta) - delta2*math.Sin(4.0*xi)*math.Cosh(4.0*eta) - delta3*math.Sin(6.0*xi)*math.Cosh(6.0*eta) - delta4*math.Sin(8.0*xi)*math.Cosh(8.0*eta)
	eta_prim := eta - delta1*math.Cos(2.0*xi)*math.Sinh(2.0*eta) - delta2*math.Cos(4.0*xi)*math.Sinh(4.0*eta) - delta3*math.Cos(6.0*xi)*math.Sinh(6.0*eta) - delta4*math.Cos(8.0*xi)*math.Sinh(8.0*eta)
	phi_star := math.Asin(math.Sin(xi_prim) / math.Cosh(eta_prim))
	delta_lambda := math.Atan(math.Sinh(eta_prim) / math.Cos(xi_prim))
	lon_radian := LambdaZero + delta_lambda
	lat_radian := phi_star + math.Sin(phi_star)*math.Cos(phi_star)*(Astar+Bstar*math.Pow(math.Sin(phi_star), 2)+Cstar*math.Pow(math.Sin(phi_star), 4)+Dstar*math.Pow(math.Sin(phi_star), 6))

	return lat_radian * 180.0 / math.Pi, lon_radian * 180.0 / math.Pi
}

func drawCircle(x, y, r float64) {

	//@TODO: Should speed this up by pre-computing all these cos() and sin() calculations and storing in a lookup table.
	gl.Begin(gl.TRIANGLE_FAN)
	//		gl.Color3d(me.red, me.green, me.blue)

	gl.Vertex2d(x, y)

	pi2 := 2 * math.Pi

	num := 36
	dTheta := pi2 / float64(num)
	theta := float64(0)
	for i := 0; i < num; i++ {

		theta += dTheta

		dx := math.Cos(theta) * r
		dy := math.Sin(theta) * r

		gl.Vertex2d(x+dx, y+dy)
	}

	theta += dTheta

	dx := math.Cos(theta) * r
	dy := math.Sin(theta) * r

	gl.Vertex2d(x+dx, y+dy)

	gl.End()
}

// Arc draws an arc with a positive angle (clockwise)
func Arc(gc draw2d.GraphicContext, xc, yc, width, height float64) {
	// draw an arc
	xc += width / 2
	yc += height / 2
	radiusX, radiusY := width/2, height/2
	startAngle := 45 * (math.Pi / 180.0) /* angles are specified */
	angle := 135 * (math.Pi / 180.0)     /* clockwise in radians           */
	gc.SetLineWidth(width / 10)
	gc.SetLineCap(draw2d.ButtCap)
	gc.SetStrokeColor(image.Black)
	gc.MoveTo(xc+math.Cos(startAngle)*radiusX, yc+math.Sin(startAngle)*radiusY)
	gc.ArcTo(xc, yc, radiusX, radiusY, startAngle, angle)
	gc.Stroke()

	// fill a circle
	gc.SetStrokeColor(color.NRGBA{255, 0x33, 0x33, 0x80})
	gc.SetFillColor(color.NRGBA{255, 0x33, 0x33, 0x80})
	gc.SetLineWidth(width / 20)

	gc.MoveTo(xc+math.Cos(startAngle)*radiusX, yc+math.Sin(startAngle)*radiusY)
	gc.LineTo(xc, yc)
	gc.LineTo(xc-radiusX, yc)
	gc.Stroke()

	gc.MoveTo(xc, yc)
	gc.ArcTo(xc, yc, width/10.0, height/10.0, 0, 2*math.Pi)
	gc.Fill()
}

// Returns a Point populated with the lat and lng coordinates of transposing the origin point the distance (in meters) supplied by the compass bearing (in degrees) supplied.
// Original Implementation from: http://www.movable-type.co.uk/scripts/latlong.html
func (p *Point) PointAtDistanceAndBearing(dist float64, bearing float64) *Point {

	dr := dist / EARTH_RADIUS

	bearing = (bearing * (math.Pi / 180.0))

	lat1 := (p.lat * (math.Pi / 180.0))
	lng1 := (p.lng * (math.Pi / 180.0))

	lat2_part1 := math.Sin(lat1) * math.Cos(dr)
	lat2_part2 := math.Cos(lat1) * math.Sin(dr) * math.Cos(bearing)

	lat2 := math.Asin(lat2_part1 + lat2_part2)

	lng2_part1 := math.Sin(bearing) * math.Sin(dr) * math.Cos(lat1)
	lng2_part2 := math.Cos(dr) - (math.Sin(lat1) * math.Sin(lat2))

	lng2 := lng1 + math.Atan2(lng2_part1, lng2_part2)
	lng2 = math.Mod((lng2+3*math.Pi), (2*math.Pi)) - math.Pi

	lat2 = lat2 * (180.0 / math.Pi)
	lng2 = lng2 * (180.0 / math.Pi)

	return &Point{lat: lat2, lng: lng2}
}

// Approximate a circular arc of fewer than π/2
// radians with cubic Bézier curve.
func partialArc(p *pdf.Path, x, y, r vg.Length, a1, a2 float64) {
	a := (a2 - a1) / 2
	x4 := r * vg.Length(math.Cos(a))
	y4 := r * vg.Length(math.Sin(a))
	x1 := x4
	y1 := -y4

	const k = 0.5522847498 // some magic constant
	f := k * vg.Length(math.Tan(a))
	x2 := x1 + f*y4
	y2 := y1 + f*x4
	x3 := x2
	y3 := -y2

	// Rotate and translate points into position.
	ar := a + a1
	sinar := vg.Length(math.Sin(ar))
	cosar := vg.Length(math.Cos(ar))
	x2r := x2*cosar - y2*sinar + x
	y2r := x2*sinar + y2*cosar + y
	x3r := x3*cosar - y3*sinar + x
	y3r := x3*sinar + y3*cosar + y
	x4 = r*vg.Length(math.Cos(a2)) + x
	y4 = r*vg.Length(math.Sin(a2)) + y
	p.Curve(pdfPoint(x2r, y2r), pdfPoint(x3r, y3r), pdfPoint(x4, y4))
}

func (m *mbody) Initialize() (y0 []float64) {
	n := len(m.mass)
	y0 = make([]float64, n*6)

	rf1 := 4 * math.Pi / 8
	rf2 := 2 * math.Pi / float64(n)

	for i := range m.mass {
		i1 := float64(i + 1)
		m.mass[i] = (0.3 + 0.1*(math.Cos(i1*rf1)+1.0)) / float64(n)
		rad := 1.7 + math.Cos(i1*0.75)
		v := 0.22 * math.Sqrt(rad)
		ci := math.Cos(i1 * rf2)
		si := math.Sin(i1 * rf2)

		ip := 6 * i
		y0[ip] = rad * ci
		y0[ip+1] = rad * si
		y0[ip+2] = 0.4 * si
		y0[ip+3] = -v * si
		y0[ip+4] = v * ci
		y0[ip+5] = 0
	}
	return
}

func delayGPS(source string, destination string) (int, error) {
	src := strings.Split(source, "/")
	lat1, err := strconv.ParseFloat(src[0], 64)
	if err != nil {
		return -1, err
	}

	lon1, err := strconv.ParseFloat(src[1], 64)
	if err != nil {
		return -1, err
	}

	dest := strings.Split(destination, "/")
	lat2, err := strconv.ParseFloat(dest[0], 64)
	if err != nil {
		return -1, err
	}

	lon2, err := strconv.ParseFloat(dest[1], 64)
	if err != nil {
		return -1, err
	}

	radius := float64(6371)

	dlat := (lat2 - lat1) / (180 / math.Pi)
	dlon := (lon2 - lon1) / (180 / math.Pi)

	a := math.Sin(dlat/2)*math.Sin(dlat/2) + math.Cos(lat1/(180*math.Pi))*math.Cos(lat2/(180*math.Pi))*math.Sin(dlon/2)*math.Sin(dlon/2)
	c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
	d := radius * c
	speed := float64(139)

	return int(math.Floor(d/speed + 0.5)), nil
}

func gradient(x float64, y float64) (xd float64, yd float64) {
	xd = (2 * x * math.Cos(math.Pow(x, 2)+math.Pow(y, 2)) * math.Cos(y+math.Exp(x))) -
		(math.Exp(x) * math.Sin(math.Pow(x, 2)+math.Pow(y, 2)) * math.Sin(y+math.Exp(x)))
	yd = (2 * y * math.Cos(math.Pow(x, 2)+math.Pow(y, 2)) * math.Cos(y+math.Exp(x))) -
		(math.Sin(math.Pow(x, 2)+math.Pow(y, 2)) * math.Sin(y+math.Exp(x)))
	return
}

func (c *OutlineCone) Paths() Paths {
	center := Vector{0, 0, 0}
	hyp := center.Sub(c.Eye).Length()
	opp := c.Radius
	theta := math.Asin(opp / hyp)
	adj := opp / math.Tan(theta)
	d := math.Cos(theta) * adj
	// r := math.Sin(theta) * adj
	w := center.Sub(c.Eye).Normalize()
	u := w.Cross(c.Up).Normalize()
	c0 := c.Eye.Add(w.MulScalar(d))
	a0 := c0.Add(u.MulScalar(c.Radius * 1.01))
	b0 := c0.Add(u.MulScalar(-c.Radius * 1.01))

	var p0 Path
	for a := 0; a < 360; a++ {
		x := c.Radius * math.Cos(Radians(float64(a)))
		y := c.Radius * math.Sin(Radians(float64(a)))
		p0 = append(p0, Vector{x, y, 0})
	}
	return Paths{
		p0,
		{{a0.X, a0.Y, 0}, {0, 0, c.Height}},
		{{b0.X, b0.Y, 0}, {0, 0, c.Height}},
	}
}

// AssignEulerRotation assigns Euler angle rotations to the rotation part of the matrix and sets the remaining elements to their ident value.
func (mat *T) AssignEulerRotation(yHead, xPitch, zRoll float64) *T {
	sinH := math.Sin(yHead)
	cosH := math.Cos(yHead)
	sinP := math.Sin(xPitch)
	cosP := math.Cos(xPitch)
	sinR := math.Sin(zRoll)
	cosR := math.Cos(zRoll)

	mat[0][0] = cosR*cosH - sinR*sinP*sinH
	mat[1][0] = -sinR * cosP
	mat[2][0] = cosR*sinH + sinR*sinP*cosH
	mat[3][0] = 0

	mat[0][1] = sinR*cosH + cosR*sinP*sinH
	mat[1][1] = cosR * cosP
	mat[2][1] = sinR*sinH - cosR*sinP*cosH
	mat[3][1] = 0

	mat[0][2] = -cosP * sinH
	mat[1][2] = sinP
	mat[2][2] = cosP * cosH
	mat[3][2] = 0

	mat[0][3] = 0
	mat[1][3] = 0
	mat[2][3] = 0
	mat[3][3] = 1

	return mat
}

func readSphereNormal(r io.Reader) (Vec3, error) {
	var result Vec3
	var zenith uint8
	var azimuth uint8
	var err error

	zenith, err = readU8(r)
	if err != nil {
		return result, err
	}

	azimuth, err = readU8(r)
	if err != nil {
		return result, err
	}

	latitude := float64(zenith) * (math.Pi * 2.0) / 255.0
	longitude := float64(azimuth) * (math.Pi * 2.0) / 255.0
	latsin := math.Sin(latitude)

	result.X = float32(math.Cos(longitude) * latsin)
	result.Y = float32(math.Sin(longitude) * latsin)
	result.Z = float32(math.Cos(latitude))

	return result, nil
}

func distance(p1, p2 location) float64 {
	var dlat float64 = p1.lat - p2.lat
	var dlong float64 = p1.long - p2.long

	var a float64 = math.Pow(math.Sin(dlat/2), 2) + math.Cos(p1.lat)*math.Cos(p2.lat)*math.Pow(math.Sin(dlong/2), 2)
	return 2 * R * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
}

func (i img) drawCurve(c curve) {
	red := byte((c.color >> 16))
	green := byte((c.color >> 8))
	blue := byte(c.color)

	startAngle := c.start * 2 * math.Pi
	angle := (c.end - c.start) * 2 * math.Pi
	endAngle := startAngle + angle
	radius := float64(c.level * i.levelWidth)
	radiusOuter := radius + float64(i.levelWidth)
	i.ctx.SetStrokeColor(color.RGBA{0, 0, 0, 0})
	i.ctx.SetFillColor(color.RGBA{red, green, blue, 0xFF})

	i.ctx.MoveTo(
		i.centerX+math.Cos(startAngle)*radius,
		i.centerY+math.Sin(startAngle)*radius,
	)
	i.ctx.ArcTo(i.centerX, i.centerY, radius, radius, startAngle, angle)

	i.ctx.LineTo(
		i.centerX+math.Cos(endAngle)*radiusOuter,
		i.centerY+math.Sin(endAngle)*radiusOuter,
	)
	i.ctx.ArcTo(i.centerX, i.centerY, radiusOuter, radiusOuter, endAngle, -angle)

	i.ctx.LineTo(
		i.centerX+math.Cos(startAngle)*radius,
		i.centerY+math.Sin(startAngle)*radius,
	)

	i.ctx.FillStroke()
}

// from: http://stackoverflow.com/questions/7316963/drawing-a-circle-google-static-maps
func (t *MealServlet) generate_polyline_code(lat, lng float64) string {
	r_earth := 6371000
	pi := math.Pi

	lat = (lat * pi) / 180
	lng = (lng * pi) / 180
	d := float64(250) / float64(r_earth) // diameter of circle

	points := make([]*Point, 0)
	// generate the points. Adjust granularity using the incrementor
	for i := 0; i <= 360; i++ {
		brng := float64(i) * pi / float64(180)
		log.Println(i)
		p_lat := math.Asin(math.Sin(lat)*math.Cos(d) + math.Cos(lat)*math.Sin(d)*math.Cos(brng))
		p_lng := ((lng + math.Atan2(math.Sin(brng)*math.Sin(d)*math.Cos(lat),
			math.Cos(d)-math.Sin(lat)*math.Sin(p_lat))) * 180) / pi
		p_lat = (p_lat * 180) / pi
		point := new(Point)
		point.Lat = p_lat
		point.Lng = p_lng
		log.Println(p_lat)
		log.Println(p_lng)
		points = append(points, point)
	}
	return EncodePolyline(points)
}

// RotY returns a rotation matrix rotating r degrees around the y axis.
func RotY(r float64) Mat4 {
	r *= deg
	return Mat4{[4]float64{math.Cos(r), 0, math.Sin(r), 0},
		[4]float64{0, 1, 0, 0},
		[4]float64{-math.Sin(r), 0, math.Cos(r), 0},
		[4]float64{0, 0, 0, 1}}
}