/*
 * 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 "raycommon.glsl"
#include "wavefront.glsl"

hitAttributeEXT vec2 attribs;

// clang-format off
layout(location = 0) rayPayloadInEXT hitPayload prd;
layout(location = 1) rayPayloadEXT bool isShadowed;
layout(location = 2) rayPayloadEXT int hitLanternInstance;

layout(buffer_reference, scalar) buffer Vertices {Vertex v[]; }; // Positions of an object
layout(buffer_reference, scalar) buffer Indices {ivec3 i[]; }; // Triangle indices
layout(buffer_reference, scalar) buffer Materials {WaveFrontMaterial m[]; }; // Array of all materials on an object
layout(buffer_reference, scalar) buffer MatIndices {int i[]; }; // Material ID for each triangle
layout(set = 0, binding = eTlas) uniform accelerationStructureEXT topLevelAS;
layout(set = 0, binding = eLanterns) buffer LanternArray { LanternIndirectEntry lanterns[]; } lanterns;

layout(set = 1, binding = eObjDescs, scalar) buffer ObjDesc_ { ObjDesc i[]; } objDesc;
layout(set = 1, binding = eTextures) uniform sampler2D textureSamplers[];

layout(push_constant) uniform _PushConstantRay { PushConstantRay pcRay; };
// clang-format on


void main()
{
  // Object data
  ObjDesc    objResource = objDesc.i[gl_InstanceCustomIndexEXT];
  MatIndices matIndices  = MatIndices(objResource.materialIndexAddress);
  Materials  materials   = Materials(objResource.materialAddress);
  Indices    indices     = Indices(objResource.indexAddress);
  Vertices   vertices    = Vertices(objResource.vertexAddress);

  // Indices of the triangle
  ivec3 ind = indices.i[gl_PrimitiveID];

  // Vertex of the triangle
  Vertex v0 = vertices.v[ind.x];
  Vertex v1 = vertices.v[ind.y];
  Vertex v2 = vertices.v[ind.z];

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

  // Computing the coordinates of the hit position
  const vec3 pos      = v0.pos * barycentrics.x + v1.pos * barycentrics.y + v2.pos * barycentrics.z;
  const vec3 worldPos = vec3(gl_ObjectToWorldEXT * vec4(pos, 1.0));  // Transforming the position to world space

  // Computing the normal at hit position
  const vec3 nrm      = v0.nrm * barycentrics.x + v1.nrm * barycentrics.y + v2.nrm * barycentrics.z;
  const vec3 worldNrm = normalize(vec3(nrm * gl_WorldToObjectEXT));  // Transforming the normal to world space

  // Vector toward the light
  vec3  L;
  vec3  colorIntensity = vec3(pcRay.lightIntensity);
  float lightDistance  = 100000.0;

  // ray direction is towards lantern, if in lantern pass.
  if(pcRay.lanternPassNumber >= 0)
  {
    LanternIndirectEntry lantern = lanterns.lanterns[pcRay.lanternPassNumber];
    vec3                 lDir    = vec3(lantern.x, lantern.y, lantern.z) - worldPos;
    lightDistance                = length(lDir);
    vec3 color                   = vec3(lantern.red, lantern.green, lantern.blue);
    // Lantern light decreases linearly. Not physically accurate, but looks good
    // and avoids a hard "edge" at the radius limit. Use a constant value
    // if lantern debug is enabled to clearly see the covered screen rectangle.
    float distanceFade = pcRay.lanternDebug != 0 ? 0.3 : max(0, (lantern.radius - lightDistance) / lantern.radius);
    colorIntensity     = color * lantern.brightness * distanceFade;
    L                  = normalize(lDir);
  }
  // Non-lantern pass may have point light...
  else if(pcRay.lightType == 0)
  {
    vec3 lDir      = pcRay.lightPosition - worldPos;
    lightDistance  = length(lDir);
    colorIntensity = vec3(pcRay.lightIntensity / (lightDistance * lightDistance));
    L              = normalize(lDir);
  }
  else  // or directional light.
  {
    L = normalize(pcRay.lightPosition);
  }

  // Material of the object
  int               matIdx = matIndices.i[gl_PrimitiveID];
  WaveFrontMaterial mat    = materials.m[matIdx];


  // Diffuse
  vec3 diffuse = computeDiffuse(mat, L, worldNrm);
  if(mat.textureId >= 0)
  {
    uint txtId    = mat.textureId + objDesc.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(worldNrm, L) > 0)
  {
    float tMin   = 0.001;
    float tMax   = lightDistance;
    vec3  origin = gl_WorldRayOriginEXT + gl_WorldRayDirectionEXT * gl_HitTEXT;
    vec3  rayDir = L;

    // Ordinary shadow from the simple tutorial.
    if(pcRay.lanternPassNumber < 0)
    {
      isShadowed = true;
      uint flags = gl_RayFlagsTerminateOnFirstHitEXT | gl_RayFlagsOpaqueEXT | gl_RayFlagsSkipClosestHitShaderEXT;
      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)
      );
    }
    // Lantern shadow ray. Cast a ray towards the lantern whose lighting is being
    // added this pass. Only the closest hit shader for lanterns will set
    // hitLanternInstance (payload 2) to non-negative value.
    else
    {
      // Skip ray if no light would be added anyway.
      if(colorIntensity == vec3(0))
      {
        isShadowed = true;
      }
      else
      {
        uint flags         = gl_RayFlagsOpaqueEXT;
        hitLanternInstance = -1;
        traceRayEXT(topLevelAS,  // acceleration structure
                    flags,       // rayFlags
                    0xFF,        // cullMask
                    2,           // sbtRecordOffset : lantern shadow hit groups start at index 2.
                    0,           // sbtRecordStride
                    2,           // missIndex       : lantern shadow miss shader is number 2.
                    origin,      // ray origin
                    tMin,        // ray min range
                    rayDir,      // ray direction
                    tMax,        // ray max range
                    2            // payload (location = 2)
        );
        // Did we hit the lantern we expected?
        isShadowed = (hitLanternInstance != pcRay.lanternPassNumber);
      }
    }

    if(isShadowed)
    {
      attenuation = 0.1;
    }
    else
    {
      // Specular
      specular = computeSpecular(mat, gl_WorldRayDirectionEXT, L, worldNrm);
    }
  }

  prd.hitValue         = colorIntensity * (attenuation * (diffuse + specular));
  prd.additiveBlending = true;
}