forked from bartvdbraak/blender
21bc1a99ba
This is an implementation that is about 1.5-2.1 times faster. It gives a result that is on average 6° different from the old implementation. The difference is because normals (Ng, N, N') are not selected to be coplanar, but instead reflection R is lifted the least amount and the N' is computed as a bisector. Differential Revision: https://developer.blender.org/D10084
228 lines
6.5 KiB
C
228 lines
6.5 KiB
C
/*
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* Parts adapted from Open Shading Language with this license:
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*
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* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
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* All Rights Reserved.
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*
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* Modifications Copyright 2011, Blender Foundation.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Sony Pictures Imageworks nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __KERNEL_MONTECARLO_CL__
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#define __KERNEL_MONTECARLO_CL__
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CCL_NAMESPACE_BEGIN
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/* distribute uniform xy on [0,1] over unit disk [-1,1] */
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ccl_device void to_unit_disk(float *x, float *y)
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{
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float phi = M_2PI_F * (*x);
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float r = sqrtf(*y);
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*x = r * cosf(phi);
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*y = r * sinf(phi);
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}
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/* return an orthogonal tangent and bitangent given a normal and tangent that
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* may not be exactly orthogonal */
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ccl_device void make_orthonormals_tangent(const float3 N, const float3 T, float3 *a, float3 *b)
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{
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*b = normalize(cross(N, T));
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*a = cross(*b, N);
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}
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/* sample direction with cosine weighted distributed in hemisphere */
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ccl_device_inline void sample_cos_hemisphere(
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const float3 N, float randu, float randv, float3 *omega_in, float *pdf)
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{
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to_unit_disk(&randu, &randv);
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float costheta = sqrtf(max(1.0f - randu * randu - randv * randv, 0.0f));
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float3 T, B;
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make_orthonormals(N, &T, &B);
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*omega_in = randu * T + randv * B + costheta * N;
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*pdf = costheta * M_1_PI_F;
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}
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/* sample direction uniformly distributed in hemisphere */
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ccl_device_inline void sample_uniform_hemisphere(
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const float3 N, float randu, float randv, float3 *omega_in, float *pdf)
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{
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float z = randu;
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float r = sqrtf(max(0.0f, 1.0f - z * z));
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float phi = M_2PI_F * randv;
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float x = r * cosf(phi);
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float y = r * sinf(phi);
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float3 T, B;
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make_orthonormals(N, &T, &B);
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*omega_in = x * T + y * B + z * N;
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*pdf = 0.5f * M_1_PI_F;
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}
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/* sample direction uniformly distributed in cone */
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ccl_device_inline void sample_uniform_cone(
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const float3 N, float angle, float randu, float randv, float3 *omega_in, float *pdf)
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{
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float zMin = cosf(angle);
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float z = zMin - zMin * randu + randu;
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float r = safe_sqrtf(1.0f - sqr(z));
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float phi = M_2PI_F * randv;
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float x = r * cosf(phi);
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float y = r * sinf(phi);
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float3 T, B;
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make_orthonormals(N, &T, &B);
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*omega_in = x * T + y * B + z * N;
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*pdf = M_1_2PI_F / (1.0f - zMin);
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}
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ccl_device_inline float pdf_uniform_cone(const float3 N, float3 D, float angle)
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{
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float zMin = cosf(angle);
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float z = dot(N, D);
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if (z > zMin) {
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return M_1_2PI_F / (1.0f - zMin);
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}
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return 0.0f;
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}
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/* sample uniform point on the surface of a sphere */
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ccl_device float3 sample_uniform_sphere(float u1, float u2)
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{
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float z = 1.0f - 2.0f * u1;
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float r = sqrtf(fmaxf(0.0f, 1.0f - z * z));
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float phi = M_2PI_F * u2;
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float x = r * cosf(phi);
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float y = r * sinf(phi);
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return make_float3(x, y, z);
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}
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ccl_device float balance_heuristic(float a, float b)
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{
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return (a) / (a + b);
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}
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ccl_device float balance_heuristic_3(float a, float b, float c)
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{
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return (a) / (a + b + c);
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}
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ccl_device float power_heuristic(float a, float b)
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{
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return (a * a) / (a * a + b * b);
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}
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ccl_device float power_heuristic_3(float a, float b, float c)
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{
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return (a * a) / (a * a + b * b + c * c);
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}
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ccl_device float max_heuristic(float a, float b)
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{
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return (a > b) ? 1.0f : 0.0f;
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}
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/* distribute uniform xy on [0,1] over unit disk [-1,1], with concentric mapping
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* to better preserve stratification for some RNG sequences */
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ccl_device float2 concentric_sample_disk(float u1, float u2)
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{
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float phi, r;
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float a = 2.0f * u1 - 1.0f;
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float b = 2.0f * u2 - 1.0f;
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if (a == 0.0f && b == 0.0f) {
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return zero_float2();
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}
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else if (a * a > b * b) {
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r = a;
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phi = M_PI_4_F * (b / a);
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}
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else {
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r = b;
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phi = M_PI_2_F - M_PI_4_F * (a / b);
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}
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return make_float2(r * cosf(phi), r * sinf(phi));
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}
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/* sample point in unit polygon with given number of corners and rotation */
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ccl_device float2 regular_polygon_sample(float corners, float rotation, float u, float v)
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{
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/* sample corner number and reuse u */
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float corner = floorf(u * corners);
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u = u * corners - corner;
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/* uniform sampled triangle weights */
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u = sqrtf(u);
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v = v * u;
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u = 1.0f - u;
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/* point in triangle */
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float angle = M_PI_F / corners;
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float2 p = make_float2((u + v) * cosf(angle), (u - v) * sinf(angle));
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/* rotate */
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rotation += corner * 2.0f * angle;
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float cr = cosf(rotation);
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float sr = sinf(rotation);
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return make_float2(cr * p.x - sr * p.y, sr * p.x + cr * p.y);
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}
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ccl_device float3 ensure_valid_reflection(float3 Ng, float3 I, float3 N)
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{
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float3 R;
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float NI = dot(N, I);
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float NgR, threshold;
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/* Check if the incident ray is coming from behind normal N. */
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if (NI > 0) {
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/* Normal reflection */
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R = (2 * NI) * N - I;
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NgR = dot(Ng, R);
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/* Reflection rays may always be at least as shallow as the incoming ray. */
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threshold = min(0.9f * dot(Ng, I), 0.01f);
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if (NgR >= threshold) {
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return N;
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}
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}
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else {
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/* Bad incident */
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R = -I;
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NgR = dot(Ng, R);
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threshold = 0.01f;
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}
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R = R + Ng * (threshold - NgR); /* Lift the reflection above the threshold. */
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return normalize(I * len(R) + R * len(I)); /* Find a bisector. */
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}
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CCL_NAMESPACE_END
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#endif /* __KERNEL_MONTECARLO_CL__ */
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