def f(self, wo: 'geo.Vector', wi: 'geo.Vector') -> 'Spectrum':
diffuse = (28. / (23. * PI)) * self.Rd * \
(Spectrum(1.) - self.Rs) * \
(1. - np.power(1. - .5 * abs_cos_theta(wi), 5)) * \
(1. - np.power(1. - .5 * abs_cos_theta(wo), 5))
wh = geo.normalize(wi + wo)
specular = self.distribution.D(wh) / \
(4. * wi.abs_dot(wh) * max(abs_cos_theta(wi), abs_cos_theta(wo))) * \
self.schlick(wi.dot(wh))
return diffuse + specular
def sample_f(self, wo: 'geo.Vector', u1: FLOAT,
u2: FLOAT) -> [FLOAT, 'geo.Vector', 'Spectrum']:
# find direction
wi = geo.Vector(-wo.x, -wo.y, wo.z)
return [
1., wi,
self.fresnel(cos_theta(wo)) * self.R / abs_cos_theta(wi)
] # 1. suggests no MC samples needed
def pdf(self, wo: 'geo.Vector', wi: 'geo.Vector') -> FLOAT:
wh = geo.normalize(wo + wi)
ct = abs_cos_theta(wh)
if wo.dot(wh) <= 0.:
return 0.
return (
(self.e + 1.) * np.power(ct, self.e)) / (2. * PI * 4. * wo.dot(wh))
def pdf(self, wo: 'geo.Vector', wi: 'geo.Vector') -> FLOAT:
"""
pdf()
Returns pdf of given direction
"""
if wo.z * wi.z > 0.:
# same hemisphere
return abs_cos_theta(wi) * INV_PI
return 0.
def f(self, wo: 'geo.Vector', wi: 'geo.Vector') -> 'Spectrum':
st_i = sin_theta(wi)
st_o = sin_theta(wo)
# \cos(\phi_i - \phi_o)
mc = 0.
if st_i > EPS and st_o > EPS:
dcos = cos_phi(wi) * cos_phi(wo) + sin_phi(wi) * sin_phi(wo)
mc = max(0., dcos)
# \sin \alpah \tan \beta
if abs_cos_theta(wi) > abs_cos_theta(wo):
sa = st_o
tb = st_i / abs_cos_theta(wi)
else:
sa = st_i
tb = st_o / abs_cos_theta(wo)
return self.R * INV_PI * (self.A + self.B * mc * sa * tb)
def D(self, wh: 'geo.Vector') -> FLOAT:
cth = abs_cos_theta(wh)
d = 1. - cth * cth
if d == 0.:
return 0.
e = (self.ex * wh.x * wh.x + self.ey * wh.y * wh.y) / d
return np.sqrt(
(self.ex + 2.) * (self.ey + 2.)) * INV_2PI * np.power(cth, e)
def pdf(self, wo: 'geo.Vector', wi: 'geo.Vector') -> FLOAT:
wh = geo.normalize(wo + wi)
ct = abs_cos_theta(wh)
ds = 1. - ct * ct
if ds > 0. and wo.dot(wh) > 0.:
return (np.sqrt((self.ex + 1.) * (self.ey + 1.)) * INV_2PI * np.power(ct,
(
self.ex * wh.x * wh.x + self.ey * wh.y * wh.y) / ds)) / \
(4. * wo.dot(wh))
else:
return 0.
def rho_hh(self, nSamples: INT, samples_1: [FLOAT],
samples_2: [FLOAT]) -> 'Spectrum':
"""
Computs hemispherical-hemispherical reflectance function.
- samples_1, samples_2
2d np array
"""
r = Spectrum(0.)
for i in range(nSamples):
wo = mc.uniform_sample_hemisphere(samples_1[i][0], samples_1[i][1])
pdf_o = INV_2PI
pdf_i, wi, f = self.sample_f(wo, samples_2[i][0], samples_2[i][1])
if pdf_i > 0.:
r += f * abs_cos_theta(wi) * abs_cos_theta(wo) / (pdf_o *
pdf_i)
r /= (PI * nSamples)
return r
def rho_hd(self, w: 'geo.Vector', samples: [FLOAT]) -> 'Spectrum':
"""
Computes hemispherical-directional reflectance function.
- w
Incoming 'geo.Vector'
- samples
2d np array
"""
r = Spectrum(0.)
for smp in samples:
pdf, wi, f = self.sample_f(w, smp[0], smp[1])
if pdf > 0.:
r += f * abs_cos_theta(wi) / pdf
r /= len(samples)
return r
def sample_f(self, wo: 'geo.Vector', u1: FLOAT,
u2: FLOAT) -> [FLOAT, 'geo.Vector', 'Spectrum']:
# find eta pair
ei, et = self.ei, self.et
if cos_theta(wo) > 0.:
ei, et = et, ei
# compute transmited ray direction
si_sq = sin_theta_sq(wo)
eta = ei / et
st_sq = eta * eta * si_sq
if st_sq >= 1.:
return [0., None, None]
ct = np.sqrt(max(0., 1. - st_sq))
if cos_theta(wo) > 0.:
ct = -ct
wi = geo.Vector(eta * (-wo.x), eta * (-wo.y), ct)
F = self.fresnel(cos_theta(wo))
return [1., wi, (et * et) / (ei * ei) * (Spectrum(1.) - F) * \
self.T / abs_cos_theta(wi)] # 1. suggests no MC samples needed
def sample_f(self, wo: 'geo.Vector', u1: FLOAT,
u2: FLOAT) -> [FLOAT, 'geo.Vector']:
# sample from first quadrant and remap to hemisphere to sample w_h
if u1 < .25:
phi, ct = self.__sample_first_quad(4. * u1, u2)
elif u1 < .5:
u1 = 4. * (.5 - u1)
phi, ct = self.__sample_first_quad(u1, u2)
phi = PI - phi
elif u1 < .75:
u1 = 4. * (u1 - .5)
phi, ct = self.__sample_first_quad(u1, u2)
phi += PI
else:
u1 = 4. * (1. - u1)
phi, ct = self.__sample_first_quad(u1, u2)
phi = 2. * PI - phi
st = np.sqrt(max(0., 1. - ct * ct))
wh = geo.spherical_direction(st, ct, phi)
if wo.z * wh.z <= 0.:
wh *= -1.
# incident direction by reflection
wi = -wo + 2. * wo.dot(wh) * wh
# compute pdf for w_i
ct = abs_cos_theta(wh)
ds = 1. - ct * ct
if ds > 0. and wo.dot(wh) > 0.:
return [(np.sqrt((self.ex + 1.) * (self.ey + 1.)) * INV_2PI * np.power(ct,
(
self.ex * wh.x * wh.x + self.ey * wh.y * wh.y) / ds)) / \
(4. * wo.dot(wh)), wi]
else:
return [0., wi]
def pdf(self, wo: 'geo.Vector', wi: 'geo.Vector') -> FLOAT:
if wo.z * wi.z <= 0.:
return 0.
return .5 * (abs_cos_theta(wi) * INV_PI +
self.distribution.pdf(wo, wi))
def D(self, wh: 'geo.Vector') -> FLOAT:
return (self.e + 2) * INV_2PI * np.power(abs_cos_theta(wh), self.e)
def G(self, wo: 'geo.Vector', wi: 'geo.Vector', wh: 'geo.Vector') -> FLOAT:
return min(
1.,
min((2. * abs_cos_theta(wh) * abs_cos_theta(wo) / wo.abs_dot(wh)),
(2. * abs_cos_theta(wh) * abs_cos_theta(wi) / wo.abs_dot(wh))))
