Init, test raylib & math things

vec3.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"math"
+)
+
+type Vector3 struct {
+	X, Y, Z float64
+}
+
+func (u Vector3) Add(v Vector3) Vector3 {
+	return Vector3{u.X + v.X, u.Y + v.Y, u.Z + v.Z}
+}
+
+func (u Vector3) Neg() Vector3 {
+	return Vector3{-u.X, -u.Y, -u.Z}
+}
+
+func (u Vector3) Sub(v Vector3) Vector3 {
+	return u.Add(v.Neg())
+}
+
+func (u Vector3) Scale(a float64) Vector3 {
+	return Vector3{a * u.X, a * u.Y, a * u.Z}
+}
+
+func (u Vector3) Dot(v Vector3) float64 {
+	return u.X*v.X + u.Y*v.Y + u.Z*v.Z
+}
+
+func (u Vector3) Cross(v Vector3) Vector3 {
+	return Vector3{u.Y*v.Z - u.Z*v.Y, u.Z*v.X - u.X*v.Z, u.X*v.Y - u.Y*v.X}
+}
+
+func (u Vector3) LengthSquared() float64 {
+	return u.Dot(u)
+}
+
+func (u Vector3) Length() float64 {
+	return math.Sqrt(u.LengthSquared())
+}
+
+func (u Vector3) Normalized() Vector3 {
+	return u.Scale(1.0 / u.Length())
+}
+
+func (u Vector3) Round() Vector3 {
+	round := math.Round
+	return Vector3{round(u.X), round(u.Y), round(u.Z)}
+}
+
+// i incident, n normal. Both vector should be normalized
+func Reflect(i Vector3, n Vector3) Vector3 {
+	y := i.Dot(n)
+	return i.Add(n.Scale(2 * y))
+}
+
+// Todo : Refract
+
+// Rodrigues' rotation formula. rotVector should be normalized
+func rotate(u Vector3, rotVector Vector3, angle float64) Vector3 {
+	cos, sin := math.Cos(angle), math.Sin(angle)
+	vec1 := u.Scale(cos)
+	vec2 := rotVector.Cross(u).Scale(sin)
+	vec3 := rotVector.Scale(rotVector.Dot(u) * (1 - cos))
+	return vec1.Add(vec2).Add(vec3)
+}
+
+func (v Vector3) Unpack() (float64, float64, float64) {
+	return v.X, v.Y, v.Z
+}