Use dep to vendor things

vendor/github.com/go-gl/mathgl/mgl32/conv.go

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+// Copyright 2014 The go-gl Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package mgl32
+
+import (
+	"math"
+)
+
+// Converts 3-dimensional cartesian coordinates (x,y,z) to spherical
+// coordinates with radius r, inclination theta, and azimuth phi.
+//
+// All angles are in radians.
+func CartesianToSpherical(coord Vec3) (r, theta, phi float32) {
+	r = coord.Len()
+	theta = float32(math.Acos(float64(coord[2] / r)))
+	phi = float32(math.Atan2(float64(coord[1]), float64(coord[0])))
+
+	return
+}
+
+// Converts 3-dimensional cartesian coordinates (x,y,z) to cylindrical
+// coordinates with radial distance r, azimuth phi, and height z.
+//
+// All angles are in radians.
+func CartesianToCylindical(coord Vec3) (rho, phi, z float32) {
+	rho = float32(math.Hypot(float64(coord[0]), float64(coord[1])))
+
+	phi = float32(math.Atan2(float64(coord[1]), float64(coord[0])))
+
+	z = coord[2]
+
+	return
+}
+
+// Converts spherical coordinates with radius r, inclination theta,
+// and azimuth phi to cartesian coordinates (x,y,z).
+//
+// Angles are in radians.
+func SphericalToCartesian(r, theta, phi float32) Vec3 {
+	st, ct := math.Sincos(float64(theta))
+	sp, cp := math.Sincos(float64(phi))
+
+	return Vec3{r * float32(st*cp), r * float32(st*sp), r * float32(ct)}
+}
+
+// Converts spherical coordinates with radius r, inclination theta,
+// and azimuth phi to cylindrical coordinates with radial distance r,
+// azimuth phi, and height z.
+//
+// Angles are in radians
+func SphericalToCylindrical(r, theta, phi float32) (rho, phi2, z float32) {
+	s, c := math.Sincos(float64(theta))
+
+	rho = r * float32(s)
+	z = r * float32(c)
+	phi2 = phi
+
+	return
+}
+
+// Converts cylindrical coordinates with radial distance r,
+// azimuth phi, and height z to spherical coordinates with radius r,
+// inclination theta, and azimuth phi.
+//
+// Angles are in radians
+func CylindircalToSpherical(rho, phi, z float32) (r, theta, phi2 float32) {
+	r = float32(math.Hypot(float64(rho), float64(z)))
+	phi2 = phi
+	theta = float32(math.Atan2(float64(rho), float64(z)))
+
+	return
+}
+
+// Converts cylindrical coordinates with radial distance r,
+// azimuth phi, and height z to cartesian coordinates (x,y,z)
+//
+// Angles are in radians.
+func CylindricalToCartesian(rho, phi, z float32) Vec3 {
+	s, c := math.Sincos(float64(phi))
+
+	return Vec3{rho * float32(c), rho * float32(s), z}
+}
+
+// Converts degrees to radians
+func DegToRad(angle float32) float32 {
+	return angle * float32(math.Pi) / 180
+}
+
+// Converts radians to degrees
+func RadToDeg(angle float32) float32 {
+	return angle * 180 / float32(math.Pi)
+}