// ======================================================================== //
// Copyright 2009-2013 Intel Corporation                                    //
//                                                                          //
// 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.                                           //
// ======================================================================== //

#include "../common/tutorial/tutorial_device.h"

struct ISPCTriangle 
{
  int v0;                /*< first triangle vertex */
  int v1;                /*< second triangle vertex */
  int v2;                /*< third triangle vertex */
  int materialID;        /*< material of triangle */
};

struct ISPCMaterial
{
  int illum;             /*< illumination model */
  
  float d;               /*< dissolve factor, 1=opaque, 0=transparent */
  float Ns;              /*< specular exponent */
  float Ni;              /*< optical density for the surface (index of refraction) */
  
  Vec3f Ka;              /*< ambient reflectivity */
  Vec3f Kd;              /*< diffuse reflectivity */
  Vec3f Ks;              /*< specular reflectivity */
  Vec3f Tf;              /*< transmission filter */
};

struct ISPCMesh
{
  Vec3fa* positions;    //!< vertex position array
  Vec3fa* normals;       //!< vertex normal array
  Vec2f* texcoords;     //!< vertex texcoord array
  ISPCTriangle* triangles;  //!< list of triangles
  int numVertices;
  int numTriangles;
};

struct ISPCScene
{
  ISPCMesh** meshes;         //!< list of meshes
  ISPCMaterial* materials;  //!< material list
  int numMeshes;
  int numMaterials;
};

/* scene data */
extern "C" ISPCScene* g_ispc_scene;
RTCScene g_scene = NULL;

/* render function to use */
renderPixelFunc renderPixel;

/* called by the C++ code for initialization */
extern "C" void device_init (int8* cfg)
{
  /* initialize ray tracing core */
  rtcInit(cfg);

  /* set start render mode */
  renderPixel = renderPixelStandard;
}

RTCScene convertScene(ISPCScene* scene_in)
{
  /* create scene */
  RTCScene scene_out = rtcNewScene(RTC_SCENE_STATIC,RTC_INTERSECT1);

  /* add all meshes to the scene */
  for (int i=0; i<scene_in->numMeshes; i++)
  {
    /* get ith mesh */
    ISPCMesh* mesh = scene_in->meshes[i];

    /* create a triangle mesh */
    unsigned int geometry = rtcNewTriangleMesh (scene_out, RTC_GEOMETRY_STATIC, mesh->numTriangles, mesh->numVertices);

#if 1
    /* share vertex buffer */
    rtcSetBuffer(scene_out, geometry, RTC_VERTEX_BUFFER, mesh->positions, 0, sizeof(Vec3fa      ));
    //rtcSetBuffer(scene_out, geometry, RTC_INDEX_BUFFER,  mesh->triangles, 0, sizeof(ISPCTriangle));

    /* set triangles */
    Triangle* triangles = (Triangle*) rtcMapBuffer(scene_out,geometry,RTC_INDEX_BUFFER);
    for (int j=0; j<mesh->numTriangles; j++) {
      triangles[j].v0 = mesh->triangles[j].v0;
      triangles[j].v1 = mesh->triangles[j].v1;
      triangles[j].v2 = mesh->triangles[j].v2;
    }
    rtcUnmapBuffer(scene_out,geometry,RTC_INDEX_BUFFER);

#elif 0
    Vec3f* positions = new Vec3f[mesh->numVertices+1];
    for (int j=0; j<mesh->numVertices; j++) {
      positions[j].x = mesh->positions[j].x;
      positions[j].y = mesh->positions[j].y;
      positions[j].z = mesh->positions[j].z;
    }
    rtcSetBuffer(scene_out, geometry, RTC_VERTEX_BUFFER, positions, 0, sizeof(Vec3f));
    rtcSetBuffer(scene_out, geometry, RTC_INDEX_BUFFER,  mesh->triangles, 0, sizeof(ISPCTriangle));
#else

    /* set vertices */
    Vertex* vertices = (Vertex*) rtcMapBuffer(scene_out,geometry,RTC_VERTEX_BUFFER); 
    for (int j=0; j<mesh->numVertices; j++) {
      vertices[j].x = mesh->positions[j].x;
      vertices[j].y = mesh->positions[j].y;
      vertices[j].z = mesh->positions[j].z;
    }
    rtcUnmapBuffer(scene_out,geometry,RTC_VERTEX_BUFFER); 

    /* set triangles */
    Triangle* triangles = (Triangle*) rtcMapBuffer(scene_out,geometry,RTC_INDEX_BUFFER);
    for (int j=0; j<mesh->numTriangles; j++) {
      triangles[j].v0 = mesh->triangles[j].v0;
      triangles[j].v1 = mesh->triangles[j].v1;
      triangles[j].v2 = mesh->triangles[j].v2;
    }
    rtcUnmapBuffer(scene_out,geometry,RTC_INDEX_BUFFER);
#endif
  }

  /* commit changes to scene */
  rtcCommit (scene_out);
  return scene_out;
}

/* task that renders a single screen tile */
Vec3fa renderPixelStandard(int x, int y, const Vec3fa& vx, const Vec3fa& vy, const Vec3fa& vz, const Vec3fa& p)
{
  /* initialize ray */
  RTCRay ray;
  ray.org = p;
  ray.dir = normalize(add(mul(x,vx), mul(y,vy), vz));
  ray.tnear = 0.0f;
  ray.tfar = inf;
  ray.geomID = RTC_INVALID_GEOMETRY_ID;
  ray.primID = RTC_INVALID_GEOMETRY_ID;
  ray.mask = -1;
  ray.time = 0;
  
  /* intersect ray with scene */
  rtcIntersect(g_scene,ray);
  
  /* shade background black */
  if (ray.geomID == RTC_INVALID_GEOMETRY_ID) return Vec3f(0.0f);
  
  /* shade all rays that hit something */
  Vec3f color = Vec3f(0.0f);
#if 1 // FIXME: pointer gather not implemented on ISPC for Xeon Phi
  ISPCMesh* mesh = g_ispc_scene->meshes[ray.geomID];
  ISPCTriangle* tri = &mesh->triangles[ray.primID];

  /* load material ID */
  int materialID = tri->materialID;

  /* interpolate shading normal */
  Vec3f n0 = Vec3f(mesh->normals[tri->v0]);
  Vec3f n1 = Vec3f(mesh->normals[tri->v1]);
  Vec3f n2 = Vec3f(mesh->normals[tri->v2]);
  float u = ray.u, v = ray.v, w = 1.0f-ray.u-ray.v;
  Vec3f Ns = add(add(mul(w,n0),mul(u,n1)),mul(v,n2));
  Ns = normalize(Ns);

#else

  int materialID = 0;
  Vec3f Ns = Vec3f(0.0f);
  foreach_unique (geomID in ray.geomID) 
  {
    ISPCMesh* mesh = g_ispc_scene->meshes[geomID];
    
    foreach_unique (primID in ray.primID) 
    {
      ISPCTriangle* tri = &mesh->triangles[primID];
      
      /* load material ID */
      materialID = tri->materialID;

      /* interpolate shading normal */
      Vec3f n0 = Vec3f(mesh->normals[tri->v0]);
      Vec3f n1 = Vec3f(mesh->normals[tri->v1]);
      Vec3f n2 = Vec3f(mesh->normals[tri->v2]);
      float u = ray.u, v = ray.v, w = 1.0f-ray.u-ray.v;
      Ns = add(add(mul(w,n0),mul(u,n1)),mul(v,n2));
    }
  }
  Ns = normalize(Ns);
#endif
  ISPCMaterial* material = &g_ispc_scene->materials[materialID];
  color = material->Kd;

  /* apply ambient light */
  Vec3f Nf = faceforward(Ns,neg(ray.dir),ray.Ng);
  //Vec3fa Ng = normalize(ray.Ng);
  //Vec3f Nf = dot(ray.dir,Ng) < 0.0f ? Ng : neg(Ng);
  color = mul(color,dot(ray.dir,Nf));    
  return color;
}

/* task that renders a single screen tile */
void renderTile(int taskIndex, int* pixels,
                     const int width,
                     const int height, 
                     const float time,
                     const Vec3f& vx, 
                     const Vec3f& vy, 
                     const Vec3f& vz, 
                     const Vec3f& p,
                     const int numTilesX, 
                     const int numTilesY)
{
  const int tileY = taskIndex / numTilesX;
  const int tileX = taskIndex - tileY * numTilesX;
  const int x0 = tileX * TILE_SIZE_X;
  const int x1 = min(x0+TILE_SIZE_X,width);
  const int y0 = tileY * TILE_SIZE_Y;
  const int y1 = min(y0+TILE_SIZE_Y,height);

  for (int y = y0; y<y1; y++) for (int x = x0; x<x1; x++)
  {
    /* calculate pixel color */
    Vec3f color = renderPixel(x,y,vx,vy,vz,p);

    /* write color to framebuffer */
    unsigned int r = (unsigned int) (255.0f * clamp(color.x,0.0f,1.0f));
    unsigned int g = (unsigned int) (255.0f * clamp(color.y,0.0f,1.0f));
    unsigned int b = (unsigned int) (255.0f * clamp(color.z,0.0f,1.0f));
    pixels[y*width+x] = (b << 16) + (g << 8) + r;
  }
}

/* called by the C++ code to render */
extern "C" void device_render (int* pixels,
                           const int width,
                           const int height, 
                           const float time,
                           const Vec3f& vx, 
                           const Vec3f& vy, 
                           const Vec3f& vz, 
                           const Vec3f& p)
{
  /* create scene */
  if (g_scene == NULL)
    g_scene = convertScene(g_ispc_scene);

  /* render image */
  const int numTilesX = (width +TILE_SIZE_X-1)/TILE_SIZE_X;
  const int numTilesY = (height+TILE_SIZE_Y-1)/TILE_SIZE_Y;
  launch_renderTile(numTilesX*numTilesY,pixels,width,height,time,vx,vy,vz,p,numTilesX,numTilesY); 
  rtcDebug();
}

/* called by the C++ code for cleanup */
extern "C" void device_cleanup ()
{
  rtcDeleteScene (g_scene);
  rtcExit();
}