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worker.go
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worker.go
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package main
import (
"math"
"math/rand"
"sync"
)
type worker struct {
id int
size int
cam *camera
wg *sync.WaitGroup
img *image
}
func (w *worker) render() {
// Always signal that this goroutine is done once we are done with all our rows.
defer w.wg.Done()
// Seed the random generator
s := rand.Uint32()
seed := &s
// If *procs = 8, we render every other 8th row starting with row w.id.
for y := w.id; y < w.size; y += *procs {
k := (w.size - y - 1) * 3 * w.size
// Loop through all the columns.
for x := (w.size - 1); x >= 0; x-- {
// The base color.
p := vector{X: 13, Y: 13, Z: 13}
// Cast of 64 rays; for a faux depth of field.
for i := 0; i < 64; i++ {
t := w.cam.up.Scale(rnd(seed) - 0.5).Scale(99).Add(w.cam.right.Scale(rnd(seed) - 0.5).Scale(99))
orig := vector{X: -5, Y: 16, Z: 8}.Add(t)
dir := t.Scale(-1).Add(w.cam.up.Scale(rnd(seed) + float64(x)*w.cam.ar).Add(w.cam.right.Scale(rnd(seed) + float64(y)*w.cam.ar)).Add(w.cam.eyeOffset).Scale(16)).Normalize()
p = sampler(orig, dir, seed).Scale(3.5).Add(p)
}
// Clamp the values and store them in the image.
w.img.data[k] = clamp(p.X)
k++
w.img.data[k] = clamp(p.Y)
k++
w.img.data[k] = clamp(p.Z)
k++
}
}
}
func sampler(orig, dir vector, seed *uint32) vector {
st, dist, bounce := tracer(orig, dir)
obounce := bounce
// If we hit the sky, early return!
if st == sMissUpward {
p := 1 - dir.Z
return vector{X: 1, Y: 1, Z: 1}.Scale(p)
}
// Intersection coordinate.
h := orig.Add(dir.Scale(dist))
// Director of light (+ random delta for soft shadows.)
l := vector{X: 9 + rnd(seed), Y: 9 + rnd(seed), Z: 16}.Add(h.Scale(-1)).Normalize()
// Lambertian factor.
b := l.DotProduct(bounce)
// sf is a hack put in because Go doesn't support ternary operator.
sf := 1.0
if b < 0 {
b, sf = 0, 0
} else {
var st status
if st, dist, bounce = tracer(h, l); st != sMissUpward {
b, sf = 0, 0
}
}
// If we hit the ground, early return!
if st == sMissDownward {
h = h.Scale(0.2)
fc := vector{X: 3, Y: 3, Z: 3}
if int(math.Ceil(h.X)+math.Ceil(h.Y))&1 == 1 {
fc = vector{X: 3, Y: 1, Z: 1}
}
return fc.Scale(b*0.2 + 0.1)
}
// Half vector.
r := dir.Add(obounce.Scale(obounce.DotProduct(dir.Scale(-2))))
// Calculate the color p.
p := math.Pow(l.DotProduct(r.Scale(sf)), 99)
// Recursively trace the path along, always scaling the next bounce by a factor of 0.5
return vector{X: p, Y: p, Z: p}.Add(sampler(h, r, seed).Scale(0.5))
}
type status int
const (
sMissUpward = iota // Hit the sky?
sMissDownward // Hit the ground
sHit // Hit an object
)
// Tracer calculates the minimum distance to a intersecting (object, ground, sky) along with the bounce vector
// from the said object.
func tracer(orig, dir vector) (st status, dist float64, bounce vector) {
// First case (assumption) is that we will hit the sky.
st, dist, bounce = sMissUpward, 1e9, vector{X: 0, Y: 0, Z: 0}
// If we are pointing towards the ground:
p := -orig.Z / dir.Z
if 0.01 < p {
st, dist, bounce = sMissDownward, p, vector{X: 0, Y: 0, Z: 1}
}
// Iterate through all the objects checking if there is a possible hit.
for i, _ := range objects {
// The sphere location is in objects[i]
p := orig.Add(objects[i])
b := p.DotProduct(dir)
b2 := b * b
c := p.DotProduct(p) - 1
// If b^2 - c > 0
if b2 > c {
q := b2 - c
s := -b - math.Sqrt(q)
// There is a hit, and it is at a closer distance! So s becomes the new smaller dist.
if s > 0.01 && s < dist {
st, dist, bounce = sHit, s, p.Add(dir.Scale(dist)).Normalize()
}
}
}
return
}