/*
 * 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

#extension GL_EXT_shader_explicit_arithmetic_types_int64 : require
#extension GL_EXT_buffer_reference2 : require


#include "binding.glsl"
#include "gltf.glsl"
#include "raycommon.glsl"

hitAttributeEXT vec2 attribs;

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

layout(set = 0, binding = 0 ) uniform accelerationStructureEXT topLevelAS;
layout(set = 0, binding = 2) readonly buffer _InstanceInfo {PrimMeshInfo primInfo[];};

//layout(set = 1, binding = B_MATERIALS) readonly buffer _MaterialBuffer {GltfShadeMaterial materials[];};


layout(buffer_reference, scalar) readonly buffer Vertices  { vec3 v[]; };
layout(buffer_reference, scalar) readonly buffer Indices   { uint i[]; };
layout(buffer_reference, scalar) readonly buffer Normals   { vec3 n[]; };
layout(buffer_reference, scalar) readonly buffer TexCoords { vec2 t[]; };
layout(buffer_reference, scalar) readonly buffer Materials { GltfShadeMaterial m[]; };

layout(set = 1, binding = B_SCENEDESC ) readonly buffer SceneDesc_ { SceneDesc sceneDesc; };
layout(set = 1, binding = B_TEXTURES) uniform sampler2D texturesMap[]; // all textures

// clang-format on

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


void main()
{
  // Retrieve the Primitive mesh buffer information
  PrimMeshInfo pinfo = primInfo[gl_InstanceCustomIndexEXT];

  // Getting the 'first index' for this mesh (offset of the mesh + offset of the triangle)
  uint indexOffset  = pinfo.indexOffset + (3 * gl_PrimitiveID);
  uint vertexOffset = pinfo.vertexOffset;           // Vertex offset as defined in glTF
  uint matIndex     = max(0, pinfo.materialIndex);  // material of primitive mesh

  Materials gltfMat   = Materials(sceneDesc.materialAddress);
  Vertices  vertices  = Vertices(sceneDesc.vertexAddress);
  Indices   indices   = Indices(sceneDesc.indexAddress);
  Normals   normals   = Normals(sceneDesc.normalAddress);
  TexCoords texCoords = TexCoords(sceneDesc.uvAddress);
  Materials materials = Materials(sceneDesc.materialAddress);


  // Getting the 3 indices of the triangle (local)
  ivec3 triangleIndex = ivec3(indices.i[indexOffset + 0], indices.i[indexOffset + 1], indices.i[indexOffset + 2]);
  triangleIndex += ivec3(vertexOffset);  // (global)

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

  // Vertex of the triangle
  const vec3 pos0           = vertices.v[triangleIndex.x];
  const vec3 pos1           = vertices.v[triangleIndex.y];
  const vec3 pos2           = vertices.v[triangleIndex.z];
  const vec3 position       = pos0 * barycentrics.x + pos1 * barycentrics.y + pos2 * barycentrics.z;
  const vec3 world_position = vec3(gl_ObjectToWorldEXT * vec4(position, 1.0));

  // Normal
  const vec3 nrm0         = normals.n[triangleIndex.x];
  const vec3 nrm1         = normals.n[triangleIndex.y];
  const vec3 nrm2         = normals.n[triangleIndex.z];
  vec3       normal       = normalize(nrm0 * barycentrics.x + nrm1 * barycentrics.y + nrm2 * barycentrics.z);
  const vec3 world_normal = normalize(vec3(normal * gl_WorldToObjectEXT));
  const vec3 geom_normal  = normalize(cross(pos1 - pos0, pos2 - pos0));

  // TexCoord
  const vec2 uv0       = texCoords.t[triangleIndex.x];
  const vec2 uv1       = texCoords.t[triangleIndex.y];
  const vec2 uv2       = texCoords.t[triangleIndex.z];
  const vec2 texcoord0 = uv0 * barycentrics.x + uv1 * barycentrics.y + uv2 * barycentrics.z;

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

  // Material of the object
  GltfShadeMaterial mat = materials.m[matIndex];

  // Diffuse
  vec3 diffuse = computeDiffuse(mat, L, world_normal);
  if(mat.pbrBaseColorTexture > -1)
  {
    uint txtId = mat.pbrBaseColorTexture;
    diffuse *= texture(texturesMap[nonuniformEXT(txtId)], texcoord0).xyz;
  }

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

  // Tracing shadow ray only if the light is visible from the surface
  if(dot(world_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, world_normal);
    }
  }

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