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package main
import (
"math"
"math/rand"
)
type Vec3D struct {
x, y, z float64
}
func (vec Vec3D) Invert() Vec3D {
return Vec3D{-vec.x, -vec.y, -vec.z}
}
func (vec Vec3D) Length() float64 {
return math.Sqrt(DotProduct(vec, vec))
}
func (vec Vec3D) Unit() Vec3D {
length := vec.Length()
if length == 0 {
return vec
}
return ScalarProduct(1.0/length, vec)
}
func (vec Vec3D) Reflect(normal Vec3D) Vec3D {
return SubVec3D(vec, ScalarProduct(2*DotProduct(vec, normal), normal))
}
func AddVec3D(vec1 Vec3D, vec2 Vec3D) Vec3D {
return Vec3D{vec1.x + vec2.x, vec1.y + vec2.y, vec1.z + vec2.z}
}
func SubVec3D(vec1 Vec3D, vec2 Vec3D) Vec3D {
return AddVec3D(vec1, vec2.Invert())
}
func ScalarProduct(scalar float64, vec Vec3D) Vec3D {
return Vec3D{scalar * vec.x, scalar * vec.y, scalar * vec.z}
}
func DotProduct(vec1 Vec3D, vec2 Vec3D) float64 {
return vec1.x*vec2.x + vec1.y*vec2.y + vec1.z*vec2.z
}
func CrossProduct(vec1 Vec3D, vec2 Vec3D) Vec3D {
return Vec3D{
vec1.y*vec2.z - vec1.z*vec2.y,
vec1.z*vec2.x - vec1.x*vec2.z,
vec1.x*vec2.y - vec1.y*vec2.x,
}
}
func RandomInUnitSphere() Vec3D {
for {
point := Vec3D{2*rand.Float64() - 1, 2*rand.Float64() - 1, 2*rand.Float64() - 1}
if point.Length() < 1.0 {
return point
}
}
}
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