/*
 * 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
 */

#version 450
#extension GL_ARB_separate_shader_objects : enable
#extension GL_EXT_nonuniform_qualifier : enable
#extension GL_GOOGLE_include_directive : enable
#extension GL_EXT_scalar_block_layout : enable

#extension GL_EXT_shader_explicit_arithmetic_types_int64 : require
#extension GL_EXT_buffer_reference2 : require

#include "gltf.glsl"
#include "host_device.h"

layout(push_constant) uniform _PushConstantRaster
{
  PushConstantRaster pcRaster;
};

// clang-format off
// Incoming 
layout(location = 1) in vec3 i_worldPos;
layout(location = 2) in vec3 i_worldNrm;
layout(location = 3) in vec3 i_viewDir;
layout(location = 4) in vec2 i_texCoord;
// Outgoing
layout(location = 0) out vec4 o_color;
// Buffers
layout(buffer_reference, scalar) buffer  GltfMaterial { GltfShadeMaterial m[]; };
layout(set = 0, binding = eSceneDesc ) readonly buffer SceneDesc_ { SceneDesc sceneDesc; } ;
layout(set = 0, binding = eTextures) uniform sampler2D[] textureSamplers;
// clang-format on


void main()
{
  // Material of the object
  GltfMaterial      gltfMat = GltfMaterial(sceneDesc.materialAddress);
  GltfShadeMaterial mat     = gltfMat.m[pcRaster.materialId];

  vec3 N = normalize(i_worldNrm);

  // Vector toward light
  vec3  L;
  float lightIntensity = pcRaster.lightIntensity;
  if(pcRaster.lightType == 0)
  {
    vec3  lDir     = pcRaster.lightPosition - i_worldPos;
    float d        = length(lDir);
    lightIntensity = pcRaster.lightIntensity / (d * d);
    L              = normalize(lDir);
  }
  else
  {
    L = normalize(pcRaster.lightPosition);
  }


  // Diffuse
  vec3 diffuse = computeDiffuse(mat, L, N);
  if(mat.pbrBaseColorTexture > -1)
  {
    uint txtId      = mat.pbrBaseColorTexture;
    vec3 diffuseTxt = texture(textureSamplers[nonuniformEXT(txtId)], i_texCoord).xyz;
    diffuse *= diffuseTxt;
  }

  // Specular
  vec3 specular = computeSpecular(mat, i_viewDir, L, N);

  // Result
  o_color = vec4(lightIntensity * (diffuse + specular), 1);
}