func sampler(orig, dir vector.Vector, seed *uint32) vector.Vector {
st, dist, bounce := tracer(orig, dir)
obounce := bounce
if st == missUpward {
p := 1 - dir.Z
p = p * p
p = p * p
return vector.Vector{X: 0.7, Y: 0.6, Z: 1}.Scale(p)
}
h := orig.Add(dir.Scale(dist))
l := vector.Vector{X: 9 + rnd(seed), Y: 9 + rnd(seed), Z: 16}.Add(h.Scale(-1)).Normalize()
b := l.DotProduct(bounce)
sf := 1.0
if b < 0 {
b = 0
sf = 0
} else {
var st status
if st, dist, bounce = tracer(h, l); st != missUpward {
b = 0
sf = 0
}
}
if st == missDownward {
h = h.Scale(0.2)
fc := vector.Vector{X: 3, Y: 3, Z: 3}
if int(math.Ceil(h.X)+math.Ceil(h.Y))&1 == 1 {
fc = vector.Vector{X: 3, Y: 1, Z: 1}
}
return fc.Scale(b*0.2 + 0.1)
}
r := dir.Add(obounce.Scale(obounce.DotProduct(dir.Scale(-2))))
p := l.DotProduct(r.Scale(sf))
p33 := p * p // p ** 2
p33 = p33 * p33 // p ** 4
p33 = p33 * p33 // p ** 8
p33 = p33 * p33 // p ** 16
p33 = p33 * p33 // p ** 32
p33 = p33 * p // p ** 33
p = p33 * p33 * p33
return vector.Vector{X: p, Y: p, Z: p}.Add(sampler(h, r, seed).Scale(0.5))
}
