IMAGE_WIDTH = 256
IMAGE_HEIGHT = 256
NSUBSAMPLES = 2
NAO_SAMPLES = 8
class Vec
def initialize(x, y, z)
@x = x
@y = y
@z = z
end
attr_accessor :x, :y, :z
def vadd(b)
Vec.new(@x + b.x, @y + b.y, @z + b.z)
end
def vsub(b)
Vec.new(@x - b.x, @y - b.y, @z - b.z)
end
def vcross(b)
Vec.new(@y * b.z - @z * b.y,
@z * b.x - @x * b.z,
@x * b.y - @y * b.x)
end
def vdot(b)
@x * b.x + @y * b.y + @z * b.z
end
def vlength
Math.sqrt(@x * @x + @y * @y + @z * @z)
end
def vnormalize
len = vlength
v = Vec.new(@x, @y, @z)
if len > 1.0e-17 then
v.x = v.x / len
v.y = v.y / len
v.z = v.z / len
end
v
end
end
class Sphere
def initialize(center, radius)
@center = center
@radius = radius
end
attr_reader :center, :radius
def intersect(ray, isect)
rs = ray.org.vsub(@center)
b = rs.vdot(ray.dir)
c = rs.vdot(rs) - (@radius * @radius)
d = b * b - c
if d > 0.0 then
t = - b - Math.sqrt(d)
if t > 0.0 and t < isect.t then
isect.t = t
isect.hit = true
isect.pl = Vec.new(ray.org.x + ray.dir.x * t,
ray.org.y + ray.dir.y * t,
ray.org.z + ray.dir.z * t)
n = isect.pl.vsub(@center)
isect.n = n.vnormalize
else
0.0
end
end
nil
end
end
class Plane
def initialize(p, n)
@p = p
@n = n
end
def intersect(ray, isect)
d = -@p.vdot(@n)
v = ray.dir.vdot(@n)
v0 = v
if v < 0.0 then
v0 = -v
end
if v0 < 1.0e-17 then
return
end
t = -(ray.org.vdot(@n) + d) / v
if t > 0.0 and t < isect.t then
isect.hit = true
isect.t = t
isect.n = @n
isect.pl = Vec.new(ray.org.x + t * ray.dir.x,
ray.org.y + t * ray.dir.y,
ray.org.z + t * ray.dir.z)
end
nil
end
end
class Ray
def initialize(org, dir)
@org = org
@dir = dir
end
attr_accessor :org, :dir
end
class Isect
def initialize
@t = 10000000.0
@hit = false
@pl = Vec.new(0.0, 0.0, 0.0)
@n = Vec.new(0.0, 0.0, 0.0)
end
attr_accessor :t, :hit, :pl, :n
end
def clamp(f)
i = f * 255.5
if i > 255.0 then
i = 255.0
end
if i < 0.0 then
i = 0.0
end
i.to_i
end
def otherBasis(basis, n)
basis[2] = Vec.new(n.x, n.y, n.z)
basis[1] = Vec.new(0.0, 0.0, 0.0)
if n.x < 0.6 and n.x > -0.6 then
basis[1].x = 1.0
elsif n.y < 0.6 and n.y > -0.6 then
basis[1].y = 1.0
elsif n.z < 0.6 and n.z > -0.6 then
basis[1].z = 1.0
else
basis[1].x = 1.0
end
basis[0] = basis[1].vcross(basis[2])
basis[0] = basis[0].vnormalize
basis[1] = basis[2].vcross(basis[0])
basis[1] = basis[1].vnormalize
end
class Scene
def initialize
@spheres = Array.new
@spheres[0] = Sphere.new(Vec.new(-2.0, 0.0, -3.5), 0.5)
@spheres[1] = Sphere.new(Vec.new(-0.5, 0.0, -3.0), 0.5)
@spheres[2] = Sphere.new(Vec.new(1.0, 0.0, -2.2), 0.5)
@plane = Plane.new(Vec.new(0.0, -0.5, 0.0), Vec.new(0.0, 1.0, 0.0))
end
def ambient_occlusion(isect)
basis = Array.new
otherBasis(basis, isect.n)
ntheta = NAO_SAMPLES
nphi = NAO_SAMPLES
eps = 0.0001
occlusion = 0.0
p0 = Vec.new(isect.pl.x + eps * isect.n.x,
isect.pl.y + eps * isect.n.y,
isect.pl.z + eps * isect.n.z)
nphi.times do |j|
ntheta.times do |i|
r = rand
phi = 2.0 * 3.14159265 * rand
x = Math.cos(phi) * Math.sqrt(1.0 - r)
y = Math.sin(phi) * Math.sqrt(1.0 - r)
z = Math.sqrt(r)
rx = x * basis[0].x + y * basis[1].x + z * basis[2].x
ry = x * basis[0].y + y * basis[1].y + z * basis[2].y
rz = x * basis[0].z + y * basis[1].z + z * basis[2].z
raydir = Vec.new(rx, ry, rz)
ray = Ray.new(p0, raydir)
occisect = Isect.new
@spheres[0].intersect(ray, occisect)
@spheres[1].intersect(ray, occisect)
@spheres[2].intersect(ray, occisect)
@plane.intersect(ray, occisect)
if occisect.hit then
occlusion = occlusion + 1.0
else
0.0
end
end
end
occlusion = (ntheta.to_f * nphi.to_f - occlusion) / (ntheta.to_f * nphi.to_f)
Vec.new(occlusion, occlusion, occlusion)
end
def render(w, h, nsubsamples)
cnt = 0
nsf = nsubsamples.to_f
h.times do |y|
w.times do |x|
rad = Vec.new(0.0, 0.0, 0.0)
nsubsamples.times do |v|
nsubsamples.times do |u|
cnt = cnt + 1
wf = w.to_f
hf = h.to_f
xf = x.to_f
yf = y.to_f
uf = u.to_f
vf = v.to_f
px = (xf + (uf / nsf) - (wf / 2.0)) / (wf / 2.0)
py = -(yf + (vf / nsf) - (hf / 2.0)) / (hf / 2.0)
eye = Vec.new(px, py, -1.0).vnormalize
ray = Ray.new(Vec.new(0.0, 0.0, 0.0), eye)
isect = Isect.new
@spheres[0].intersect(ray, isect)
@spheres[1].intersect(ray, isect)
@spheres[2].intersect(ray, isect)
@plane.intersect(ray, isect)
if isect.hit then
col = ambient_occlusion(isect)
rad.x = rad.x + col.x
rad.y = rad.y + col.y
rad.z = rad.z + col.z
end
end
end
r = rad.x / (nsf * nsf)
g = rad.y / (nsf * nsf)
b = rad.z / (nsf * nsf)
printf("%c", clamp(r))
printf("%c", clamp(g))
printf("%c", clamp(b))
end
nil
end
nil
end
end
alias printf_orig printf
def printf *args
end
printf("P6\n")
printf("%d %d\n", IMAGE_WIDTH, IMAGE_HEIGHT)
printf("255\n", IMAGE_WIDTH, IMAGE_HEIGHT)
Scene.new.render(IMAGE_WIDTH, IMAGE_HEIGHT, NSUBSAMPLES)
undef printf
alias printf printf_orig