/*
 * Copyright (c) 2019-2021, NVIDIA CORPORATION.  All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-FileCopyrightText: Copyright (c) 2019-2021 NVIDIA CORPORATION
 * SPDX-License-Identifier: Apache-2.0
 */

#include "host_device.h"

vec3 computeDiffuse(WaveFrontMaterial mat, vec3 lightDir, vec3 normal)
{
  // Lambertian
  float dotNL = max(dot(normal, lightDir), 0.0);
  vec3  c     = mat.diffuse * dotNL;
  if(mat.illum >= 1)
    c += mat.ambient;
  return c;
}

vec3 computeSpecular(WaveFrontMaterial mat, vec3 viewDir, vec3 lightDir, vec3 normal)
{
  if(mat.illum < 2)
    return vec3(0);

  // Compute specular only if not in shadow
  const float kPi        = 3.14159265;
  const float kShininess = max(mat.shininess, 4.0);

  // Specular
  const float kEnergyConservation = (2.0 + kShininess) / (2.0 * kPi);
  vec3        V                   = normalize(-viewDir);
  vec3        R                   = reflect(-lightDir, normal);
  float       specular            = kEnergyConservation * pow(max(dot(V, R), 0.0), kShininess);

  return vec3(mat.specular * specular);
}