/*
 * 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 460
#extension GL_EXT_ray_tracing : require
#extension GL_EXT_nonuniform_qualifier : enable
#extension GL_EXT_scalar_block_layout : enable
#extension GL_GOOGLE_include_directive : enable
#include "raycommon.glsl"
#include "wavefront.glsl"

hitAttributeEXT vec2 attribs;

// clang-format off
layout(location = 0) rayPayloadInEXT hitPayload prd;
layout(location = 1) rayPayloadEXT bool isShadowed;

layout(binding = 0, set = 0) uniform accelerationStructureEXT topLevelAS;
layout(binding = 1, set = 1, scalar) buffer MatColorBufferObject { WaveFrontMaterial m[]; } materials[];
layout(binding = 2, set = 1, scalar) buffer ScnDesc { sceneDesc i[]; } scnDesc;
layout(binding = 3, set = 1) uniform sampler2D textureSamplers[];
layout(binding = 4, set = 1)  buffer MatIndexColorBuffer { int i[]; } matIndex[];
layout(binding = 5, set = 1, scalar) buffer Vertices { Vertex v[]; } vertices[];
layout(binding = 6, set = 1) buffer Indices { uint i[]; } indices[];

// clang-format on

layout(push_constant) uniform Constants
{
  vec4  clearColor;
  vec3  lightPosition;
  float lightIntensity;
  int   lightType;
}
pushC;


void main()
{
  // Object of this instance
  uint objId = scnDesc.i[gl_InstanceCustomIndexEXT].objId;

  // Indices of the triangle
  ivec3 ind = ivec3(indices[nonuniformEXT(objId)].i[3 * gl_PrimitiveID + 0],   //
                    indices[nonuniformEXT(objId)].i[3 * gl_PrimitiveID + 1],   //
                    indices[nonuniformEXT(objId)].i[3 * gl_PrimitiveID + 2]);  //
  // Vertex of the triangle
  Vertex v0 = vertices[nonuniformEXT(objId)].v[ind.x];
  Vertex v1 = vertices[nonuniformEXT(objId)].v[ind.y];
  Vertex v2 = vertices[nonuniformEXT(objId)].v[ind.z];

  const vec3 barycentrics = vec3(1.0 - attribs.x - attribs.y, attribs.x, attribs.y);

  // Computing the normal at hit position
  vec3 normal = v0.nrm * barycentrics.x + v1.nrm * barycentrics.y + v2.nrm * barycentrics.z;
  // Transforming the normal to world space
  normal = normalize(vec3(scnDesc.i[gl_InstanceCustomIndexEXT].transfoIT * vec4(normal, 0.0)));


  // Computing the coordinates of the hit position
  vec3 worldPos = v0.pos * barycentrics.x + v1.pos * barycentrics.y + v2.pos * barycentrics.z;
  // Transforming the position to world space
  worldPos = vec3(scnDesc.i[gl_InstanceCustomIndexEXT].transfo * vec4(worldPos, 1.0));

  // Vector toward the light
  vec3  L;
  float lightIntensity = pushC.lightIntensity;
  float lightDistance  = 100000.0;
  // Point light
  if(pushC.lightType == 0)
  {
    vec3 lDir      = pushC.lightPosition - worldPos;
    lightDistance  = length(lDir);
    lightIntensity = pushC.lightIntensity / (lightDistance * lightDistance);
    L              = normalize(lDir);
  }
  else  // Directional light
  {
    L = normalize(pushC.lightPosition - vec3(0));
  }

  // Material of the object
  int               matIdx = matIndex[nonuniformEXT(objId)].i[gl_PrimitiveID];
  WaveFrontMaterial mat    = materials[nonuniformEXT(objId)].m[matIdx];


  // Diffuse
  vec3 diffuse = computeDiffuse(mat, L, normal);
  if(mat.textureId >= 0)
  {
    uint txtId = mat.textureId + scnDesc.i[gl_InstanceCustomIndexEXT].txtOffset;
    vec2 texCoord =
        v0.texCoord * barycentrics.x + v1.texCoord * barycentrics.y + v2.texCoord * barycentrics.z;
    diffuse *= texture(textureSamplers[nonuniformEXT(txtId)], texCoord).xyz;
  }

  vec3  specular    = vec3(0);
  float attenuation = 1;

  // Tracing shadow ray only if the light is visible from the surface
  if(dot(normal, L) > 0)
  {
    float tMin   = 0.001;
    float tMax   = lightDistance;
    vec3  origin = gl_WorldRayOriginEXT + gl_WorldRayDirectionEXT * gl_HitTEXT;
    vec3  rayDir = L;
    uint  flags  = gl_RayFlagsTerminateOnFirstHitEXT | gl_RayFlagsOpaqueEXT
                 | gl_RayFlagsSkipClosestHitShaderEXT;
    isShadowed = true;
    traceRayEXT(topLevelAS,  // acceleration structure
                flags,       // rayFlags
                0xFF,        // cullMask
                0,           // sbtRecordOffset
                0,           // sbtRecordStride
                1,           // missIndex
                origin,      // ray origin
                tMin,        // ray min range
                rayDir,      // ray direction
                tMax,        // ray max range
                1            // payload (location = 1)
    );

    if(isShadowed)
    {
      attenuation = 0.3;
    }
    else
    {
      // Specular
      specular = computeSpecular(mat, gl_WorldRayDirectionEXT, L, normal);
    }
  }

  prd.hitValue = vec3(lightIntensity * attenuation * (diffuse + specular));
}