259 lines
7.1 KiB
Python
259 lines
7.1 KiB
Python
# A simple ray tracer
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# MIT license; Copyright (c) 2019 Damien P. George
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INF = 1e30
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EPS = 1e-6
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class Vec:
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def __init__(self, x, y, z):
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self.x, self.y, self.z = x, y, z
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def __neg__(self):
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return Vec(-self.x, -self.y, -self.z)
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def __add__(self, rhs):
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return Vec(self.x + rhs.x, self.y + rhs.y, self.z + rhs.z)
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def __sub__(self, rhs):
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return Vec(self.x - rhs.x, self.y - rhs.y, self.z - rhs.z)
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def __mul__(self, rhs):
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return Vec(self.x * rhs, self.y * rhs, self.z * rhs)
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def length(self):
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return (self.x ** 2 + self.y ** 2 + self.z ** 2) ** 0.5
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def normalise(self):
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l = self.length()
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return Vec(self.x / l, self.y / l, self.z / l)
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def dot(self, rhs):
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return self.x * rhs.x + self.y * rhs.y + self.z * rhs.z
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RGB = Vec
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class Ray:
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def __init__(self, p, d):
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self.p, self.d = p, d
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class View:
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def __init__(self, width, height, depth, pos, xdir, ydir, zdir):
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self.width = width
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self.height = height
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self.depth = depth
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self.pos = pos
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self.xdir = xdir
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self.ydir = ydir
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self.zdir = zdir
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def calc_dir(self, dx, dy):
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return (self.xdir * dx + self.ydir * dy + self.zdir * self.depth).normalise()
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class Light:
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def __init__(self, pos, colour, casts_shadows):
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self.pos = pos
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self.colour = colour
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self.casts_shadows = casts_shadows
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class Surface:
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def __init__(self, diffuse, specular, spec_idx, reflect, transp, colour):
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self.diffuse = diffuse
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self.specular = specular
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self.spec_idx = spec_idx
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self.reflect = reflect
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self.transp = transp
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self.colour = colour
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@staticmethod
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def dull(colour):
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return Surface(0.7, 0.0, 1, 0.0, 0.0, colour * 0.6)
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@staticmethod
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def shiny(colour):
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return Surface(0.2, 0.9, 32, 0.8, 0.0, colour * 0.3)
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@staticmethod
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def transparent(colour):
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return Surface(0.2, 0.9, 32, 0.0, 0.8, colour * 0.3)
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class Sphere:
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def __init__(self, surface, centre, radius):
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self.surface = surface
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self.centre = centre
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self.radsq = radius ** 2
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def intersect(self, ray):
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v = self.centre - ray.p
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b = v.dot(ray.d)
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det = b ** 2 - v.dot(v) + self.radsq
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if det > 0:
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det **= 0.5
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t1 = b - det
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if t1 > EPS:
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return t1
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t2 = b + det
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if t2 > EPS:
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return t2
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return INF
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def surface_at(self, v):
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return self.surface, (v - self.centre).normalise()
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class Plane:
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def __init__(self, surface, centre, normal):
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self.surface = surface
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self.normal = normal.normalise()
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self.cdotn = centre.dot(normal)
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def intersect(self, ray):
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ddotn = ray.d.dot(self.normal)
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if abs(ddotn) > EPS:
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t = (self.cdotn - ray.p.dot(self.normal)) / ddotn
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if t > 0:
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return t
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return INF
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def surface_at(self, p):
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return self.surface, self.normal
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class Scene:
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def __init__(self, ambient, light, objs):
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self.ambient = ambient
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self.light = light
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self.objs = objs
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def trace_scene(canvas, view, scene, max_depth):
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for v in range(canvas.height):
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y = (-v + 0.5 * (canvas.height - 1)) * view.height / canvas.height
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for u in range(canvas.width):
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x = (u - 0.5 * (canvas.width - 1)) * view.width / canvas.width
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ray = Ray(view.pos, view.calc_dir(x, y))
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c = trace_ray(scene, ray, max_depth)
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canvas.put_pix(u, v, c)
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def trace_ray(scene, ray, depth):
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# Find closest intersecting object
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hit_t = INF
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hit_obj = None
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for obj in scene.objs:
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t = obj.intersect(ray)
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if t < hit_t:
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hit_t = t
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hit_obj = obj
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# Check if any objects hit
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if hit_obj is None:
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return RGB(0, 0, 0)
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# Compute location of ray intersection
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point = ray.p + ray.d * hit_t
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surf, surf_norm = hit_obj.surface_at(point)
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if ray.d.dot(surf_norm) > 0:
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surf_norm = -surf_norm
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# Compute reflected ray
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reflected = ray.d - surf_norm * (surf_norm.dot(ray.d) * 2)
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# Ambient light
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col = surf.colour * scene.ambient
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# Diffuse, specular and shadow from light source
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light_vec = scene.light.pos - point
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light_dist = light_vec.length()
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light_vec = light_vec.normalise()
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ndotl = surf_norm.dot(light_vec)
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ldotv = light_vec.dot(reflected)
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if ndotl > 0 or ldotv > 0:
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light_ray = Ray(point + light_vec * EPS, light_vec)
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light_col = trace_to_light(scene, light_ray, light_dist)
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if ndotl > 0:
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col += light_col * surf.diffuse * ndotl
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if ldotv > 0:
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col += light_col * surf.specular * ldotv ** surf.spec_idx
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# Reflections
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if depth > 0 and surf.reflect > 0:
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col += trace_ray(scene, Ray(point + reflected * EPS, reflected), depth - 1) * surf.reflect
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# Transparency
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if depth > 0 and surf.transp > 0:
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col += trace_ray(scene, Ray(point + ray.d * EPS, ray.d), depth - 1) * surf.transp
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return col
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def trace_to_light(scene, ray, light_dist):
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col = scene.light.colour
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for obj in scene.objs:
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t = obj.intersect(ray)
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if t < light_dist:
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col *= obj.surface.transp
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return col
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class Canvas:
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def __init__(self, width, height):
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self.width = width
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self.height = height
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self.data = bytearray(3 * width * height)
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def put_pix(self, x, y, c):
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off = 3 * (y * self.width + x)
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self.data[off] = min(255, max(0, int(255 * c.x)))
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self.data[off + 1] = min(255, max(0, int(255 * c.y)))
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self.data[off + 2] = min(255, max(0, int(255 * c.z)))
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def write_ppm(self, filename):
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with open(filename, "wb") as f:
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f.write(bytes("P6 %d %d 255\n" % (self.width, self.height), "ascii"))
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f.write(self.data)
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def main(w, h, d):
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canvas = Canvas(w, h)
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view = View(32, 32, 64, Vec(0, 0, 50), Vec(1, 0, 0), Vec(0, 1, 0), Vec(0, 0, -1))
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scene = Scene(
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0.5,
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Light(Vec(0, 8, 0), RGB(1, 1, 1), True),
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[
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Plane(Surface.dull(RGB(1, 0, 0)), Vec(-10, 0, 0), Vec(1, 0, 0)),
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Plane(Surface.dull(RGB(0, 1, 0)), Vec(10, 0, 0), Vec(-1, 0, 0)),
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Plane(Surface.dull(RGB(1, 1, 1)), Vec(0, 0, -10), Vec(0, 0, 1)),
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Plane(Surface.dull(RGB(1, 1, 1)), Vec(0, -10, 0), Vec(0, 1, 0)),
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Plane(Surface.dull(RGB(1, 1, 1)), Vec(0, 10, 0), Vec(0, -1, 0)),
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Sphere(Surface.shiny(RGB(1, 1, 1)), Vec(-5, -4, 3), 4),
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Sphere(Surface.dull(RGB(0, 0, 1)), Vec(4, -5, 0), 4),
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Sphere(Surface.transparent(RGB(0.2, 0.2, 0.2)), Vec(6, -1, 8), 4),
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],
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)
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trace_scene(canvas, view, scene, d)
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return canvas
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# For testing
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# main(256, 256, 4).write_ppm('rt.ppm')
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###########################################################################
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# Benchmark interface
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bm_params = {
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(100, 100): (5, 5, 2),
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(1000, 100): (18, 18, 3),
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(5000, 100): (40, 40, 3),
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}
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def bm_setup(params):
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return lambda: main(*params), lambda: (params[0] * params[1] * params[2], None)
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