def test_square_to_uniform_sphere_vec(variant_scalar_rgb):
from mitsuba.core import warp
assert(ek.allclose(warp.square_to_uniform_sphere([0, 0]), [0, 0, 1]))
assert(ek.allclose(warp.square_to_uniform_sphere([0, 1]), [0, 0, -1]))
assert(ek.allclose(warp.square_to_uniform_sphere([0.5, 0.5]), [-1, 0, 0], atol=1e-7))
check_inverse(warp.square_to_uniform_sphere, warp.uniform_sphere_to_square)
check_vectorization("square_to_uniform_sphere")
def test01_coordinate_system(variant_scalar_rgb):
from mitsuba.core import coordinate_system, warp
def branchless_onb(n):
"""
Building an Orthonormal Basis, Revisited
Tom Duff, James Burgess, Per Christensen, Christophe Hery,
Andrew Kensler, Max Liani, and Ryusuke Villemin
"""
sign = ek.copysign(1.0, n[2])
a = -1.0 / (sign + n[2])
b = n[0] * n[1] * a
return (
[1.0 + sign * n[0] * n[0] * a, sign * b, -sign * n[0]],
[b, sign + n[1] * n[1] * a, -n[1]]
)
a = [0.70710678, -0. , -0.70710678]
b = [-0., 1., 0.]
assert ek.allclose(
branchless_onb([ek.sqrt(0.5), 0, ek.sqrt(0.5)]), (a, b), atol=1e-6)
assert ek.allclose(
coordinate_system([ek.sqrt(0.5), 0, ek.sqrt(0.5)]), (a, b), atol=1e-6)
for u in ek.linspace(Float, 0, 1, 10):
for v in ek.linspace(Float, 0, 1, 10):
n = warp.square_to_uniform_sphere([u, v])
s1, t1 = branchless_onb(n)
s2, t2 = coordinate_system(n)
assert ek.allclose(s1, s2, atol=1e-6)
assert ek.allclose(t1, t2, atol=1e-6)
def test01_point_sample_ray(variant_packet_spectral, spectrum_key):
# Check the correctness of the sample_ray() method
from mitsuba.core import Vector3f, warp, sample_shifted
from mitsuba.render import SurfaceInteraction3f
emitter_pos = [10, -1, 2]
emitter, spectrum = create_emitter_and_spectrum(emitter_pos, spectrum_key)
time = 0.5
wavelength_sample = [0.5, 0.33, 0.1]
dir_sample = [[0.4, 0.5, 0.3], [0.1, 0.4, 0.9]]
pos_sample = dir_sample # not being used anyway
# Sample a ray (position, direction, wavelengths) on the emitter
ray, res = emitter.sample_ray(time, wavelength_sample, pos_sample,
dir_sample)
# Sample wavelengths on the spectrum
it = SurfaceInteraction3f.zero(3)
wav, spec = spectrum.sample_spectrum(it, sample_shifted(wavelength_sample))
assert ek.allclose(res, spec * 4 * ek.pi)
assert ek.allclose(ray.time, time)
assert ek.allclose(ray.wavelengths, wav)
assert ek.allclose(ray.d, warp.square_to_uniform_sphere(dir_sample))
assert ek.allclose(ray.o, Vector3f(emitter_pos))
def test03_sample_direction(variant_packet_spectral):
# Check the correctness of the sample_direction() and pdf_direction() methods
from mitsuba.core import warp
from mitsuba.core.math import InvFourPi
from mitsuba.render import SurfaceInteraction3f
emitter, spectrum = create_emitter_and_spectrum()
it = SurfaceInteraction3f.zero(3)
# Some positions inside the unit sphere
it.p = [[-0.5, 0.3, -0.1], [0.8, -0.3, -0.2], [-0.2, 0.6, -0.6]]
it.time = 1.0
# Sample direction on the emitter
samples = [[0.4, 0.5, 0.3], [0.1, 0.4, 0.9]]
ds, res = emitter.sample_direction(it, samples)
assert ek.allclose(ds.pdf, InvFourPi)
assert ek.allclose(ds.d, warp.square_to_uniform_sphere(samples))
assert ek.allclose(emitter.pdf_direction(it, ds), InvFourPi)
assert ek.allclose(ds.time, it.time)
# Evaluate the spectrum (divide by the pdf)
spec = spectrum.eval(it) / warp.square_to_uniform_sphere_pdf(ds.d)
assert ek.allclose(res, spec)
def test02_sample_ray(variant_packet_spectral, spectrum_key):
# Check the correctness of the sample_ray() method
from mitsuba.core import Frame3f, warp, sample_shifted
from mitsuba.render import SurfaceInteraction3f
emitter, spectrum = create_emitter_and_spectrum(spectrum_key)
time = 0.5
wavelength_sample = [0.5, 0.33, 0.1]
pos_sample = [[0.2, 0.1, 0.2], [0.6, 0.9, 0.2]]
dir_sample = [[0.4, 0.5, 0.3], [0.1, 0.4, 0.9]]
# Sample a ray (position, direction, wavelengths) on the emitter
ray, res = emitter.sample_ray(time, wavelength_sample, pos_sample,
dir_sample)
# Sample wavelengths on the spectrum
it = SurfaceInteraction3f.zero(3)
wav, spec = spectrum.sample(it, sample_shifted(wavelength_sample))
assert ek.allclose(res, spec * 4 * ek.pi * ek.pi)
assert ek.allclose(ray.time, time)
assert ek.allclose(ray.wavelengths, wav)
assert ek.allclose(ray.o, warp.square_to_uniform_sphere(pos_sample))
assert ek.allclose(
ray.d,
Frame3f(-ray.o).to_world(warp.square_to_cosine_hemisphere(dir_sample)))
def sample_ray(
self,
time,
sample1, # wavelength
sample2, # pos
sample3, # dir
active):
wavelengths, spec_weight = self.m_intensity.sample(
SurfaceInteraction3f(), ek.arange(sample1), active)
trafo = self.m_world_transform.eval(ref.time)
ray = Ray3f(trafo * Point3f(0), warp.square_to_uniform_sphere(sample3),
time, wavelengths)
# print(spec_weight.class_().name())
return (ray, spec_weight * 4.0 * Pi)
def test03_sample_eval_pdf(variant_scalar_rgb, interaction):
from mitsuba.core.math import InvPi
from mitsuba.core.warp import square_to_uniform_sphere
from mitsuba.render import BSDFContext
from mitsuba.core.xml import load_string
bsdf = load_string("""<bsdf version="2.0.0" type="twosided">
<bsdf type="diffuse">
<rgb name="reflectance" value="0.1, 0.1, 0.1"/>
</bsdf>
<bsdf type="diffuse">
<rgb name="reflectance" value="0.9, 0.9, 0.9"/>
</bsdf>
</bsdf>""")
n = 5
ctx = BSDFContext()
for u in ek.arange(UInt32, n):
for v in ek.arange(UInt32, n):
interaction.wi = square_to_uniform_sphere([u / float(n-1),
v / float(n-1)])
up = ek.dot(interaction.wi, [0, 0, 1]) > 0
for x in ek.arange(UInt32, n):
for y in ek.arange(UInt32, n):
sample = [x / float(n-1), y / float(n-1)]
(bs, s_value) = bsdf.sample(ctx, interaction, 0.5, sample)
if ek.any(s_value > 0):
# Multiply by square_to_cosine_hemisphere_theta
s_value *= bs.wo[2] * InvPi
if not up:
s_value *= -1
e_value = bsdf.eval(ctx, interaction, bs.wo)
p_pdf = bsdf.pdf(ctx, interaction, bs.wo)
assert ek.allclose(s_value, e_value, atol=1e-2)
assert ek.allclose(bs.pdf, p_pdf)
assert not ek.any(ek.isnan(e_value) | ek.isnan(s_value))
def sample(self, ctx, mi, sample1, active=True):
wo = warp.square_to_uniform_sphere(sample1)
pdf = warp.square_to_uniform_sphere_pdf(wo)
return (wo, pdf)