mis.h

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/* SPDX-FileCopyrightText: 2009-2010 Sony Pictures Imageworks Inc., et al. All Rights Reserved.
 * SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Adapted code from Open Shading Language. */
 
#pragma once
 
#include "util/defines.h"
 
CCL_NAMESPACE_BEGIN
 
/* Multiple importance sampling utilities. */
 
ccl_device float balance_heuristic(const float a, const float b)
{
  return (a) / (a + b);
}
 
ccl_device float balance_heuristic_3(const float a, const float b, float c)
{
  return (a) / (a + b + c);
}
 
ccl_device float power_heuristic(const float a, const float b)
{
  return (a * a) / (a * a + b * b);
}
 
ccl_device float power_heuristic_3(const float a, const float b, float c)
{
  return (a * a) / (a * a + b * b + c * c);
}
 
ccl_device float max_heuristic(const float a, const float b)
{
  return (a > b) ? 1.0f : 0.0f;
}
 
CCL_NAMESPACE_END