// Copyright 2009 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "rkcommon/math/math.ih"

OSPRAY_BEGIN_ISPC_NAMESPACE

inline float roughnessToAlpha(float roughness)
{
  // Roughness is squared for perceptual reasons
  return max(sqr(roughness), 0.001f);
}

// [Burley, 2012, "Physically Based Shading at Disney", Course Notes, v3]
inline vec2f roughnessToAlpha(float roughness, float anisotropy)
{
  float aspect = sqrt(1.f - 0.9f * anisotropy);
  return make_vec2f(max(sqr(roughness) / aspect, 0.001f),
      max(sqr(roughness) * aspect, 0.001f));
}

OSPRAY_END_ISPC_NAMESPACE
