426 lines
No EOL
9.7 KiB
Go
426 lines
No EOL
9.7 KiB
Go
package main
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import "fmt" // for IO and standard library
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import "os" // for handling the progress bar
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import "math" // for maths
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import "unsafe" // for fast inverse square pointers
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import "math/rand" // for random
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import "time" // for random
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func init() {
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rand.Seed(time.Now().UnixNano())
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}
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// ================ VEC3 CLASS =====================
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type Vec3 struct {
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E [3]float32
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}
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//Basic vector functions
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func NewVec3(e0, e1, e2 float32) Vec3 {
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return Vec3{E: [3]float32{e0, e1, e2}}
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}
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func (v Vec3) X() float32 {
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return v.E[0]
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}
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// can be executed as v.X() in main
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func (v Vec3) Y() float32 {
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return v.E[1]
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}
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func (v Vec3) Z() float32 {
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return v.E[2]
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}
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func (v Vec3) Neg() Vec3 {
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return NewVec3(-v.E[0], -v.E[1], -v.E[2])
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}
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func (v Vec3) Get(i int) float32 {
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return v.E[i]
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}
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func (v *Vec3) Set(i int, val float32) {
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v.E[i] = val
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}
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func (v Vec3) Add(v2 Vec3) Vec3 {
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return NewVec3(v.E[0]+v2.E[0], v.E[1]+v2.E[1], v.E[2]+v2.E[2])
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}
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func (v Vec3) Mult(t float32) Vec3 {
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return NewVec3(v.E[0]*t, v.E[1]*t, v.E[2]*t)
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}
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func (v Vec3) Div(t float32) Vec3 {
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if t != 0 {
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return NewVec3(v.E[0] / t, v.E[1] / t, v.E[2] / t)
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}
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return v
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}
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func (v Vec3) Length() float32 {
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return float32(math.Sqrt(float64(v.E[0]*v.E[0] + v.E[1]*v.E[1] + v.E[2]*v.E[2])))
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}
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func (v Vec3) Length_squared() float32 {
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return v.E[0]*v.E[0] + v.E[1]*v.E[1] + v.E[2]*v.E[2]
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}
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// Vector utility functions
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func (v Vec3) String() string {
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return fmt.Sprintf("%v %v %v", v.E[0], v.E[1], v.E[2])
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}
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func (v Vec3) Sub(v2 Vec3) Vec3 {
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return NewVec3(v.E[0]-v2.E[0], v.E[1]-v2.E[1], v.E[2]-v2.E[2])
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}
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func (v Vec3) MultVec(v2 Vec3) Vec3 {
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return NewVec3(v.E[0]*v2.E[0], v.E[1]*v2.E[1], v.E[2]*v2.E[2])
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}
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func (v Vec3) DivVec(v2 Vec3) Vec3 {
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if v2.E[0] != 0 && v2.E[1] != 0 && v2.E[2] != 0 {
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return NewVec3(v.E[0]/v2.E[0], v.E[1]/v2.E[1], v.E[2]/v2.E[2])
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}
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return v
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}
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func Dot(v1 Vec3, v2 Vec3) float32 {
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return (v1.E[0]*v2.E[0] + v1.E[1]*v2.E[1] + v1.E[2]*v2.E[2])
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}
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func Cross(v1 Vec3, v2 Vec3) Vec3 {
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return NewVec3(v1.E[1]*v2.E[2] - v1.E[2]*v2.E[1],
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v1.E[2]*v2.E[0] - v1.E[0]*v2.E[2],
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v1.E[0]*v2.E[1] - v1.E[1]*v2.E[0])
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}
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func q_rsqrt(v Vec3) float32 {
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var x float32 = v.E[0]*v.E[0] + v.E[1]*v.E[1] + v.E[2]*v.E[2]
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i := *(*int32)(unsafe.Pointer(&x)) // evil floating point bit level hacking
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i = 0x5f3759df - (i >> 1) // what the fuck?
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y := *(*float32)(unsafe.Pointer(&i))
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return y
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}
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func Unit_vector(v Vec3) Vec3 {
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new_v := v.Mult(q_rsqrt(v))
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return new_v
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}
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const pi float32 = 3.1415926535897932385
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func Degrees_to_radians(degrees float32) float32 {
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return (degrees * pi) / 180.0
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}
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func RandomDouble() float32 {
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// Returns a random real in [0,1).
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return rand.Float32()
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}
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func RandomDoubleInRange(min, max float32) float32 {
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// Returns a random real in [min,max).
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return min + (max-min)*RandomDouble()
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}
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// ============== COLOUR CLASS ==============
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func Write_color(v Vec3, samples_per_pixel int) {
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// Averaging
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r := v.X() / float32(samples_per_pixel)
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g := v.Y() / float32(samples_per_pixel)
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b := v.Z() / float32(samples_per_pixel)
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// Write the translate [0, 255] value of each color component
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intensity := NewInterval(0.000, 0.999)
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fmt.Println(int(intensity.Clamp(r)* 256.0), int(intensity.Clamp(g)* 256.0), int(intensity.Clamp(b)* 256.0))
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}
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func NewColor(e0, e1, e2 float32) Vec3 {
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return Vec3{E: [3]float32{e0, e1, e2}}
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}
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// ============== RAY CLASS =================
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func NewPoint3(e0, e1, e2 float32) Vec3 {
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return Vec3{E: [3]float32{e0, e1, e2}}
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}
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type Ray struct {
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Orig Vec3
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Dir Vec3
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}
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func NewRay(orig Vec3, dir Vec3) *Ray {
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return &Ray{Orig: orig, Dir: dir}
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}
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func (r *Ray) Origin() Vec3 {
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return r.Orig
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}
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func (r *Ray) Direction() Vec3 {
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return r.Dir
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}
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func (r *Ray) At(t float32) Vec3 {
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return Vec3{
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E: [3]float32{
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r.Orig.X() + t*r.Dir.X(),
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r.Orig.Y() + t*r.Dir.Y(),
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r.Orig.Z() + t*r.Dir.Z(),
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},
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}
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}
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// =============== INTERVAL =================
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type Interval struct {
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min, max float32
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}
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func NewInterval(borders ...float32) *Interval {
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if (len(borders) == 2) {
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return &Interval{
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min: borders[0],
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max: borders[1],
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}
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} else {
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return &Interval{
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min: float32(math.Inf(1)),
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max: float32(math.Inf(-1)),
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}
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}
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}
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func (i *Interval) Contains(x float32) bool {
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return i.min <= x && x <= i.max
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}
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func (i *Interval) Surrounds(x float32) bool {
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return i.min < x && x < i.max
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}
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func (i *Interval) Clamp(x float32) float32 {
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if (x < i.min) {
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return i.min
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} else if (x > i.max) {
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return i.max
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}
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return x
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}
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var Empty *Interval = NewInterval()
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var Universe *Interval = NewInterval(float32(math.Inf(-1)), float32(math.Inf(1)))
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// =============== HIT ======================
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type Hit_record struct {
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p Vec3
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normal Vec3
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t float32
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front_face bool
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}
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func (rec *Hit_record) Set_face_normal(r *Ray, outward_normal Vec3) {
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if (Dot(r.Direction(), outward_normal) < 0) {
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rec.front_face = true
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}
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if (rec.front_face) {
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rec.normal = outward_normal
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} else {
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rec.normal = outward_normal.Neg()
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}
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}
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// =============== SPHERE ===================
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type Sphere struct {
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center Vec3
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radius float32
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}
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func (s Sphere) Hit_sphere(r *Ray, ray_t *Interval, rec *Hit_record) bool {
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oc := r.Origin().Sub(s.center)
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a := r.Direction().Length_squared()
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half_b := Dot(oc, r.Direction())
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c := oc.Length_squared() - s.radius*s.radius
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discriminant := half_b*half_b - a*c
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if (discriminant < 0) {
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return false
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}
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sqrtd := float32(math.Sqrt(float64(discriminant)))
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// find the nearest root that lies in the acceptable range
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root := (-half_b - sqrtd) / a
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if (!ray_t.Surrounds(root)) {
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root = (sqrtd-half_b) / a
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if (!ray_t.Surrounds(root)) {
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return false
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}
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}
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rec.t = root
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rec.p = r.At(rec.t)
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outward_normal := rec.p.Sub(s.center).Div(s.radius)
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rec.Set_face_normal(r, outward_normal)
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return true
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}
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// =============== HITTABLE ==================
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type Hittable struct {
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spheres []Sphere
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}
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func NewHittable() *Hittable {
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return &Hittable{}
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}
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func (hl *Hittable) Add(s Sphere) {
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hl.spheres = append(hl.spheres, s)
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}
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func (hl *Hittable) Clear() {
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hl.spheres = []Sphere{}
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}
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func (hl Hittable) Hit(r *Ray, ray_t Interval, rec *Hit_record) bool {
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var temp_rec Hit_record
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var hit_anything bool = false
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var closest_so_far float32 = ray_t.max
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for _, sphere := range hl.spheres {
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if (sphere.Hit_sphere(r, NewInterval(ray_t.min, closest_so_far), &temp_rec)) {
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hit_anything = true
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closest_so_far = temp_rec.t
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*rec = temp_rec
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}
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}
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return hit_anything
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}
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// =============== CAMERA ===================
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type Camera struct {
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aspect_ratio float32
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image_width int
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image_height int
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center Vec3
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pixel00_loc Vec3
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pixel_delta_u Vec3
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pixel_delta_v Vec3
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samples_per_pixel int
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}
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func NewCamera() *Camera {
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return &Camera{}
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}
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func Ray_color(r Ray, world *Hittable) Vec3 {
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var rec Hit_record
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if (world.Hit(&r, *NewInterval(0, float32(math.Inf(1))), &rec)) {
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return rec.normal.Add(NewColor(1,1,1)).Mult(0.5)
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}
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unit_direction := Unit_vector(r.Direction())
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a := (unit_direction.Y() + 1.0)*0.5
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return NewColor(1.0,1.0,1.0).Mult(float32(1.0-a)).Add(NewColor(0.5,0.7,1.0).Mult(a))
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}
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func (cam *Camera) Initialize() {
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// Calculate the image height
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cam.image_height = int(float32(cam.image_width) / cam.aspect_ratio)
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if cam.image_height < 1 {
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cam.image_height = 1
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}
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// Viewport
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var focal_length float32 = 1.0
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var viewport_height float32 = 2.0
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var viewport_width float32 = viewport_height * float32(cam.image_width)/float32(cam.image_height)
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cam.center = NewVec3(0,0,0)
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// Calculate the vectors across the horizontal and down the vertical viewport edges
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viewport_u := NewVec3(viewport_width, 0, 0)
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viewport_v := NewVec3(0, -viewport_height, 0)
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//Calculate the horizontal and vertical delta vectors from pixel to pixel
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cam.pixel_delta_u = viewport_u.Div(float32(cam.image_width))
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cam.pixel_delta_v = viewport_v.Div(float32(cam.image_height))
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// Calculate the location of the upper left pixel
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viewport_upper_left := cam.center.Sub(cam.center).Sub(NewVec3(0, 0, focal_length)).Sub(viewport_u.Div(2)).Sub(viewport_v.Div(2))
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cam.pixel00_loc = viewport_upper_left.Add((cam.pixel_delta_u.Add(cam.pixel_delta_v)).Div(2))
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}
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func (cam *Camera) Render(world *Hittable) {
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cam.Initialize()
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// Rendering
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fmt.Println("P3")
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fmt.Println(cam.image_width, " ", cam.image_height, "\n255")
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for j := 0; j < cam.image_height; j++ {
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fmt.Fprintf(os.Stderr, "\rScanlines remaining: %d ", cam.image_height-j)
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for i := 0; i < cam.image_width; i++ {
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pixel_color := NewColor(0,0,0)
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for sample := 0; sample < cam.samples_per_pixel; sample++ {
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r := cam.GetRay(i, j)
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pixel_color = pixel_color.Add(Ray_color(*r, world))
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}
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Write_color(pixel_color, cam.samples_per_pixel)
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}
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}
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}
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func (cam *Camera) GetRay(i, j int) *Ray {
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// Get a randomly sampled camera ray for the pixel at location i,j
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pixel_center := cam.pixel00_loc.Add(cam.pixel_delta_u.Mult(float32(i))).Add(cam.pixel_delta_v.Mult(float32(j)))
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pixel_sample := pixel_center.Add(cam.Pixel_sample_square())
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ray_direction := pixel_sample.Sub(cam.center)
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return NewRay(cam.center, ray_direction)
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}
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func (cam *Camera) Pixel_sample_square() Vec3 {
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// Returns a random point in the square surrounding a pixel at the origin
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px := -0.5 + RandomDouble()
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py := -0.5 + RandomDouble()
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return (cam.pixel_delta_u.Mult(px).Add(cam.pixel_delta_v.Mult(py)))
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}
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// =============== MAIN =====================
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func main() {
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// World
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world := NewHittable()
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world.Add(Sphere{
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center: NewVec3(0, 0, -1),
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radius: 0.5,
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})
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world.Add(Sphere{
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center: NewVec3(0, -100.5, -1),
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radius: 100,
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})
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// Image
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cam := NewCamera()
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cam.aspect_ratio = 16.0 / 9.0
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cam.image_width = 400
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cam.samples_per_pixel = 100
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cam.Render(world)
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// INFO: The pixels are written out in rows.
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// Image file can be created with
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// go run main.go > image.ppm
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} |