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/*
* Parts adapted from Open Shading Language with this license:
*
* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
* All Rights Reserved.
*
* Modifications Copyright 2011, Blender Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Sony Pictures Imageworks nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __KERNEL_MONTECARLO_CL__
#define __KERNEL_MONTECARLO_CL__
CCL_NAMESPACE_BEGIN
/// Given values x and y on [0,1], convert them in place to values on
/// [-1,1] uniformly distributed over a unit sphere. This code is
/// derived from Peter Shirley, "Realistic Ray Tracing", p. 103.
__device void to_unit_disk(float *x, float *y)
{
float r, phi;
float a = 2.0f * (*x) - 1.0f;
float b = 2.0f * (*y) - 1.0f;
if(a > -b) {
if(a > b) {
r = a;
phi = M_PI_4_F *(b/a);
} else {
r = b;
phi = M_PI_4_F *(2.0f - a/b);
}
} else {
if(a < b) {
r = -a;
phi = M_PI_4_F *(4.0f + b/a);
} else {
r = -b;
if(b != 0.0f)
phi = M_PI_4_F *(6.0f - a/b);
else
phi = 0.0f;
}
}
*x = r * cosf(phi);
*y = r * sinf(phi);
}
__device_inline void make_orthonormals(const float3 N, float3 *a, float3 *b)
{
if(N.x != N.y || N.x != N.z)
*a = make_float3(N.z-N.y, N.x-N.z, N.y-N.x); //(1,1,1)x N
else
*a = make_float3(N.z-N.y, N.x+N.z, -N.y-N.x); //(-1,1,1)x N
*a = normalize(*a);
*b = cross(N, *a);
}
__device void make_orthonormals_tangent(const float3 N, const float3 T, float3 *a, float3 *b)
{
*b = cross(N, T);
*a = cross(*b, N);
}
__device_inline void sample_cos_hemisphere(const float3 N,
float randu, float randv, float3 *omega_in, float *pdf)
{
// Default closure BSDF implementation: uniformly sample
// cosine-weighted hemisphere above the point.
to_unit_disk(&randu, &randv);
float costheta = sqrtf(max(1.0f - randu * randu - randv * randv, 0.0f));
float3 T, B;
make_orthonormals(N, &T, &B);
*omega_in = randu * T + randv * B + costheta * N;
*pdf = costheta *M_1_PI_F;
}
__device_inline void sample_uniform_hemisphere(const float3 N,
float randu, float randv,
float3 *omega_in, float *pdf)
{
float z = randu;
float r = sqrtf(max(0.f, 1.f - z*z));
float phi = 2.f * M_PI_F * randv;
float x = r * cosf(phi);
float y = r * sinf(phi);
float3 T, B;
make_orthonormals (N, &T, &B);
*omega_in = x * T + y * B + z * N;
*pdf = 0.5f * M_1_PI_F;
}
__device float3 sample_uniform_sphere(float u1, float u2)
{
float z = 1.0f - 2.0f*u1;
float r = sqrtf(fmaxf(0.0f, 1.0f - z*z));
float phi = 2.0f*M_PI_F*u2;
float x = r*cosf(phi);
float y = r*sinf(phi);
return make_float3(x, y, z);
}
__device float power_heuristic(float a, float b)
{
return (a*a)/(a*a + b*b);
}
__device float2 concentric_sample_disk(float u1, float u2)
{
float r, theta;
// Map uniform random numbers to $[-1,1]^2$
float sx = 2 * u1 - 1;
float sy = 2 * u2 - 1;
// Map square to $(r,\theta)$
// Handle degeneracy at the origin
if(sx == 0.0f && sy == 0.0f) {
return make_float2(0.0f, 0.0f);
}
if(sx >= -sy) {
if(sx > sy) {
// Handle first region of disk
r = sx;
if(sy > 0.0f) theta = sy/r;
else theta = 8.0f + sy/r;
}
else {
// Handle second region of disk
r = sy;
theta = 2.0f - sx/r;
}
}
else {
if(sx <= sy) {
// Handle third region of disk
r = -sx;
theta = 4.0f - sy/r;
}
else {
// Handle fourth region of disk
r = -sy;
theta = 6.0f + sx/r;
}
}
theta *= M_PI_4_F;
return make_float2(r * cosf(theta), r * sinf(theta));
}
__device float2 regular_polygon_sample(float corners, float rotation, float u, float v)
{
/* sample corner number and reuse u */
float corner = floorf(u*corners);
u = u*corners - corner;
/* uniform sampled triangle weights */
u = sqrtf(u);
v = v*u;
u = 1.0f - u;
/* point in triangle */
float angle = M_PI_F/corners;
float2 p = make_float2((u + v)*cosf(angle), (u - v)*sinf(angle));
/* rotate */
rotation += corner*2.0f*angle;
float cr = cosf(rotation);
float sr = sinf(rotation);
return make_float2(cr*p.x - sr*p.y, sr*p.x + cr*p.y);
}
/* Spherical coordinates <-> Cartesion direction */
__device float2 direction_to_spherical(float3 dir)
{
float theta = acosf(dir.z);
float phi = atan2f(dir.x, dir.y);
return make_float2(theta, phi);
}
__device float3 spherical_to_direction(float theta, float phi)
{
return make_float3(
sinf(theta)*cosf(phi),
sinf(theta)*sinf(phi),
cosf(theta));
}
CCL_NAMESPACE_END
#endif /* __KERNEL_MONTECARLO_CL__ */
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