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/* SPDX-License-Identifier: BSD-3-Clause
*
* Adapted from Open Shading Language
* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
* All Rights Reserved.
*
* Modifications Copyright 2011-2022 Blender Foundation. */
#pragma once
CCL_NAMESPACE_BEGIN
/* distribute uniform xy on [0,1] over unit disk [-1,1] */
ccl_device void to_unit_disk(ccl_private float *x, ccl_private float *y)
{
float phi = M_2PI_F * (*x);
float r = sqrtf(*y);
*x = r * cosf(phi);
*y = r * sinf(phi);
}
/* return an orthogonal tangent and bitangent given a normal and tangent that
* may not be exactly orthogonal */
ccl_device void make_orthonormals_tangent(const float3 N,
const float3 T,
ccl_private float3 *a,
ccl_private float3 *b)
{
*b = normalize(cross(N, T));
*a = cross(*b, N);
}
/* sample direction with cosine weighted distributed in hemisphere */
ccl_device_inline void sample_cos_hemisphere(
const float3 N, float randu, float randv, ccl_private float3 *omega_in, ccl_private float *pdf)
{
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;
}
/* sample direction uniformly distributed in hemisphere */
ccl_device_inline void sample_uniform_hemisphere(
const float3 N, float randu, float randv, ccl_private float3 *omega_in, ccl_private float *pdf)
{
float z = randu;
float r = sqrtf(max(0.0f, 1.0f - z * z));
float phi = M_2PI_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;
}
/* sample direction uniformly distributed in cone */
ccl_device_inline void sample_uniform_cone(const float3 N,
float angle,
float randu,
float randv,
ccl_private float3 *omega_in,
ccl_private float *pdf)
{
float zMin = cosf(angle);
float z = zMin - zMin * randu + randu;
float r = safe_sqrtf(1.0f - sqr(z));
float phi = M_2PI_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 = M_1_2PI_F / (1.0f - zMin);
}
ccl_device_inline float pdf_uniform_cone(const float3 N, float3 D, float angle)
{
float zMin = cosf(angle);
float z = dot(N, D);
if (z > zMin) {
return M_1_2PI_F / (1.0f - zMin);
}
return 0.0f;
}
/* sample uniform point on the surface of a sphere */
ccl_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 = M_2PI_F * u2;
float x = r * cosf(phi);
float y = r * sinf(phi);
return make_float3(x, y, z);
}
/* distribute uniform xy on [0,1] over unit disk [-1,1], with concentric mapping
* to better preserve stratification for some RNG sequences */
ccl_device float2 concentric_sample_disk(float u1, float u2)
{
float phi, r;
float a = 2.0f * u1 - 1.0f;
float b = 2.0f * u2 - 1.0f;
if (a == 0.0f && b == 0.0f) {
return zero_float2();
}
else if (a * a > b * b) {
r = a;
phi = M_PI_4_F * (b / a);
}
else {
r = b;
phi = M_PI_2_F - M_PI_4_F * (a / b);
}
return make_float2(r * cosf(phi), r * sinf(phi));
}
/* sample point in unit polygon with given number of corners and rotation */
ccl_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);
}
CCL_NAMESPACE_END
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