1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
package main
import (
"math"
"math/rand"
)
// Material generate color when hitable is hit
type Material interface {
Scatter(ray Ray, hit HitRecord) (Ray, Color)
}
// Lambertian is diffuse material
type Lambertian struct {
albedo Color
}
// Scatter for Lambertians
func (lambertian Lambertian) Scatter(ray Ray, hit HitRecord) (Ray, Color) {
// TODO: Use the correct distribution
var normal Vec3D
if DotProduct(ray.direction, hit.normal) < 0.0 {
normal = hit.normal
} else {
normal = hit.normal.Invert()
}
direction := AddVec3D(normal, RandomInUnitSphere())
scattered := Ray{hit.point, direction}
return scattered, lambertian.albedo
}
// Metal material
type Metal struct {
albedo Color
fuzz float64
}
// Scatter for Metal
func (metal Metal) Scatter(ray Ray, hit HitRecord) (Ray, Color) {
var normal Vec3D
if DotProduct(ray.direction, hit.normal) < 0.0 {
normal = hit.normal
} else {
normal = hit.normal.Invert()
}
reflected := AddVec3D(ray.direction.Unit().Reflect(normal), ScalarProduct(metal.fuzz, RandomInUnitSphere()))
scattered := Ray{hit.point, reflected}
return scattered, metal.albedo
}
// Dielectric is glass for instance
type Dielectric struct {
eta float64
}
// Scatter for Dielectric
func (dielectric Dielectric) Scatter(ray Ray, hit HitRecord) (Ray, Color) {
var etaI, etaT float64
var normal Vec3D
attenuation := Color{1.0, 1.0, 1.0}
if DotProduct(ray.direction, hit.normal) < 0.0 {
etaI, etaT = 1.0, dielectric.eta
normal = hit.normal
} else {
etaI, etaT = 1.0, dielectric.eta
normal = hit.normal.Invert()
}
vecI := ray.direction.Unit()
cosTheta := FMin(DotProduct(vecI.Invert(), normal), 1.0)
sinTheta := math.Sqrt(1.0 - cosTheta*cosTheta)
if etaI/etaT*sinTheta > 1.0 || rand.Float64() < Schlick(cosTheta, etaI, etaT) {
reflected := ray.direction.Unit().Reflect(normal)
scattered := Ray{hit.point, reflected}
return scattered, attenuation
}
refracted := Refract(vecI, normal, etaI, etaT)
scattered := Ray{hit.point, refracted}
return scattered, attenuation
}
// Schlick glass refraction probability
func Schlick(cosine float64, etaI float64, etaT float64) float64 {
r0 := (1.0 - etaI/etaT) / (1.0 + etaI/etaT)
r0 *= r0
return r0 + (1.0-r0)*math.Pow(1.0-cosine, 5)
}
|
