// ======================================================================== //
// Copyright 2009-2017 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.                                           //
// ======================================================================== //

#pragma once

#include "triangle.h"
#include "intersector_epilog.h"

/*! This intersector implements a modified version of the Moeller
 *  Trumbore intersector from the paper "Fast, Minimum Storage
 *  Ray-Triangle Intersection". In contrast to the paper we
 *  precalculate some factors and factor the calculations differently
 *  to allow precalculating the cross product e1 x e2. The resulting
 *  algorithm is similar to the fastest one of the paper "Optimizing
 *  Ray-Triangle Intersection via Automated Search". */

namespace embree
{
  namespace isa
  {
    template<int M>
      struct MoellerTrumboreHitM
    {
      __forceinline MoellerTrumboreHitM() {}

      __forceinline MoellerTrumboreHitM(const vbool<M>& valid, const vfloat<M>& U, const vfloat<M>& V, const vfloat<M>& T, const vfloat<M>& absDen, const Vec3<vfloat<M>>& Ng)
        : U(U), V(V), T(T), absDen(absDen), valid(valid), vNg(Ng) {}
      
      __forceinline void finalize() 
      {
        const vfloat<M> rcpAbsDen = rcp(absDen);
        vt = T * rcpAbsDen;
        vu = U * rcpAbsDen;
        vv = V * rcpAbsDen;
      }

      __forceinline Vec2f uv (const size_t i) const { return Vec2f(vu[i],vv[i]); }
      __forceinline float t  (const size_t i) const { return vt[i]; }
      __forceinline Vec3fa Ng(const size_t i) const { return Vec3fa(vNg.x[i],vNg.y[i],vNg.z[i]); }
      
    public:
      vfloat<M> U;
      vfloat<M> V;
      vfloat<M> T;
      vfloat<M> absDen;
      
    public:
      vbool<M> valid;
      vfloat<M> vu;
      vfloat<M> vv;
      vfloat<M> vt;
      Vec3<vfloat<M>> vNg;
    };
    
    template<int M>
      struct MoellerTrumboreIntersector1
    {
      __forceinline MoellerTrumboreIntersector1() {}

      __forceinline MoellerTrumboreIntersector1(const Ray& ray, const void* ptr) {}

      __forceinline bool intersect(const vbool<M>& valid0,
                                   Ray& ray, 
                                   const Vec3<vfloat<M>>& tri_v0, 
                                   const Vec3<vfloat<M>>& tri_e1, 
                                   const Vec3<vfloat<M>>& tri_e2, 
                                   const Vec3<vfloat<M>>& tri_Ng,
                                   MoellerTrumboreHitM<M>& hit) const
      {
        /* calculate denominator */
        vbool<M> valid = valid0;
        typedef Vec3<vfloat<M>> Vec3vfM;
        const Vec3vfM O = Vec3vfM(ray.org);
        const Vec3vfM D = Vec3vfM(ray.dir);
        const Vec3vfM C = Vec3vfM(tri_v0) - O;
        const Vec3vfM R = cross(D,C);
        const vfloat<M> den = dot(Vec3vfM(tri_Ng),D);
        const vfloat<M> absDen = abs(den);
        const vfloat<M> sgnDen = signmsk(den);
        
        /* perform edge tests */
        const vfloat<M> U = dot(R,Vec3vfM(tri_e2)) ^ sgnDen;
        const vfloat<M> V = dot(R,Vec3vfM(tri_e1)) ^ sgnDen;
        
        /* perform backface culling */        
#if defined(EMBREE_BACKFACE_CULLING)
        valid &= (den < vfloat<M>(zero)) & (U >= 0.0f) & (V >= 0.0f) & (U+V<=absDen);
#else
        valid &= (den != vfloat<M>(zero)) & (U >= 0.0f) & (V >= 0.0f) & (U+V<=absDen);
#endif
        if (likely(none(valid))) return false;
        
        /* perform depth test */
        const vfloat<M> T = dot(Vec3vfM(tri_Ng),C) ^ sgnDen;
        valid &= (T > absDen*vfloat<M>(ray.tnear)) & (T < absDen*vfloat<M>(ray.tfar));
        if (likely(none(valid))) return false;
        
        /* update hit information */
        new (&hit) MoellerTrumboreHitM<M>(valid,U,V,T,absDen,tri_Ng);
        return true;
      }

      __forceinline bool intersect(Ray& ray, 
                                   const Vec3<vfloat<M>>& tri_v0, 
                                   const Vec3<vfloat<M>>& tri_e1, 
                                   const Vec3<vfloat<M>>& tri_e2, 
                                   const Vec3<vfloat<M>>& tri_Ng,
                                   MoellerTrumboreHitM<M>& hit) const
      {
        vbool<M> valid = true;
        return intersect(valid,ray,tri_v0,tri_e1,tri_e2,tri_Ng,hit);
      }
      
      __forceinline bool intersect(Ray& ray, 
                                   const Vec3<vfloat<M>>& v0, 
                                   const Vec3<vfloat<M>>& v1, 
                                   const Vec3<vfloat<M>>& v2, 
                                   MoellerTrumboreHitM<M>& hit) const
      {
        const Vec3<vfloat<M>> e1 = v0-v1;
        const Vec3<vfloat<M>> e2 = v2-v0;
        const Vec3<vfloat<M>> Ng = cross(e1,e2);
        return intersect(ray,v0,e1,e2,Ng,hit);
      }

      __forceinline bool intersect(const vbool<M>& valid,
                                   Ray& ray, 
                                   const Vec3<vfloat<M>>& v0, 
                                   const Vec3<vfloat<M>>& v1, 
                                   const Vec3<vfloat<M>>& v2, 
                                   MoellerTrumboreHitM<M>& hit) const
      {
        const Vec3<vfloat<M>> e1 = v0-v1;
        const Vec3<vfloat<M>> e2 = v2-v0;
        const Vec3<vfloat<M>> Ng = cross(e1,e2);
        return intersect(valid,ray,v0,e1,e2,Ng,hit);
      }

      template<typename Epilog>
        __forceinline bool intersect(Ray& ray, 
                                     const Vec3<vfloat<M>>& v0, 
                                     const Vec3<vfloat<M>>& e1, 
                                     const Vec3<vfloat<M>>& e2, 
                                     const Vec3<vfloat<M>>& Ng, 
                                     const Epilog& epilog) const
      {
        MoellerTrumboreHitM<M> hit;
        if (likely(intersect(ray,v0,e1,e2,Ng,hit))) return epilog(hit.valid,hit);
        return false;
      }

      template<typename Epilog>
        __forceinline bool intersect(Ray& ray, 
                                     const Vec3<vfloat<M>>& v0, 
                                     const Vec3<vfloat<M>>& v1, 
                                     const Vec3<vfloat<M>>& v2, 
                                     const Epilog& epilog) const
      {
        MoellerTrumboreHitM<M> hit;
        if (likely(intersect(ray,v0,v1,v2,hit))) return epilog(hit.valid,hit);
        return false;
      }

      template<typename Epilog>
      __forceinline bool intersect(const vbool<M>& valid,
                                   Ray& ray, 
                                   const Vec3<vfloat<M>>& v0, 
                                   const Vec3<vfloat<M>>& v1, 
                                   const Vec3<vfloat<M>>& v2, 
                                   const Epilog& epilog) const
      {
        MoellerTrumboreHitM<M> hit;
        if (likely(intersect(valid,ray,v0,v1,v2,hit))) return epilog(hit.valid,hit);
        return false;
      }

      // ==== new interface for ray streams ====

      __forceinline bool intersectN(const Vec3<vfloat<M>>& ray_org,
                                    const Vec3<vfloat<M>>& ray_dir,
                                    const vfloat<M>& ray_tnear,
                                    const vfloat<M>& ray_tfar,
                                    const Vec3<vfloat<M>>& tri_v0, 
                                    const Vec3<vfloat<M>>& tri_e1, 
                                    const Vec3<vfloat<M>>& tri_e2, 
                                    const Vec3<vfloat<M>>& tri_Ng,
                                    MoellerTrumboreHitM<M>& hit) const
      {
        /* calculate denominator */
        typedef Vec3<vfloat<M>> Vec3vfM;
        const Vec3vfM &O = ray_org;
        const Vec3vfM &D = ray_dir;
        const Vec3vfM C = Vec3vfM(tri_v0) - O;
        const Vec3vfM R = cross(D,C);
        const vfloat<M> den = dot(Vec3vfM(tri_Ng),D);
        const vfloat<M> absDen = abs(den);
        const vfloat<M> sgnDen = signmsk(den);
        
        /* perform edge tests */
        const vfloat<M> U = dot(R,Vec3vfM(tri_e2)) ^ sgnDen;
        const vfloat<M> V = dot(R,Vec3vfM(tri_e1)) ^ sgnDen;
        
        /* perform backface culling */        
#if defined(EMBREE_BACKFACE_CULLING)
        vbool<M> valid = (den < vfloat<M>(zero)) & (U >= 0.0f) & (V >= 0.0f) & (U+V<=absDen);
#else
        vbool<M> valid = (den != vfloat<M>(zero)) & (U >= 0.0f) & (V >= 0.0f) & (U+V<=absDen);
#endif
        if (likely(none(valid))) return false;
        
        /* perform depth test */
        const vfloat<M> T = dot(Vec3vfM(tri_Ng),C) ^ sgnDen;
        valid &= (T > absDen*ray_tnear) & (T < absDen*ray_tfar);
        if (likely(none(valid))) return false;
        
        /* update hit information */
        new (&hit) MoellerTrumboreHitM<M>(valid,U,V,T,absDen,tri_Ng);
        return true;
      }

      template<typename Epilog>
        __forceinline bool intersectN(const Vec3<vfloat<M>>& ray_org,
                                      const Vec3<vfloat<M>>& ray_dir,
                                      const vfloat<M>& ray_tnear,
                                      const vfloat<M>& ray_tfar,
                                      const Vec3<vfloat<M>>& v0, 
                                      const Vec3<vfloat<M>>& e1, 
                                      const Vec3<vfloat<M>>& e2, 
                                      const Vec3<vfloat<M>>& Ng, 
                                      const Epilog& epilog) const
      {
        MoellerTrumboreHitM<M> hit;
        if (likely(intersectN(ray_org,ray_dir,ray_tnear,ray_tfar,v0,e1,e2,Ng,hit))) return epilog(hit.valid,hit);
        return false;
      }

    };
    
    template<int K>
      struct MoellerTrumboreHitK
    {
      __forceinline MoellerTrumboreHitK(const vfloat<K>& U, const vfloat<K>& V, const vfloat<K>& T, const vfloat<K>& absDen, const Vec3<vfloat<K>>& Ng)
        : U(U), V(V), T(T), absDen(absDen), Ng(Ng) {}
      
      __forceinline std::tuple<vfloat<K>,vfloat<K>,vfloat<K>,Vec3<vfloat<K>>> operator() () const
      {
        const vfloat<K> rcpAbsDen = rcp(absDen);
        const vfloat<K> t = T * rcpAbsDen;
        const vfloat<K> u = U * rcpAbsDen;
        const vfloat<K> v = V * rcpAbsDen;
        return std::make_tuple(u,v,t,Ng);
      }
      
    private:
      const vfloat<K> U;
      const vfloat<K> V;
      const vfloat<K> T;
      const vfloat<K> absDen;
      const Vec3<vfloat<K>> Ng;
    };
    
    template<int M, int K>
      struct MoellerTrumboreIntersectorK
    {
      __forceinline MoellerTrumboreIntersectorK(const vbool<K>& valid, const RayK<K>& ray) {}
      
      /*! Intersects K rays with one of M triangles. */
      template<typename Epilog>
        __forceinline vbool<K> intersectK(const vbool<K>& valid0, 
                                          //RayK<K>& ray, 
                                          const Vec3<vfloat<K>>& ray_org,
                                          const Vec3<vfloat<K>>& ray_dir,
                                          const vfloat<K>& ray_tnear,
                                          const vfloat<K>& ray_tfar,
                                          const Vec3<vfloat<K>>& tri_v0, 
                                          const Vec3<vfloat<K>>& tri_e1, 
                                          const Vec3<vfloat<K>>& tri_e2, 
                                          const Vec3<vfloat<K>>& tri_Ng, 
                                          const Epilog& epilog) const
      {
        /* ray SIMD type shortcuts */
        typedef Vec3<vfloat<K>> Vec3vfK;
        
        /* calculate denominator */
        vbool<K> valid = valid0;
        const Vec3vfK C = tri_v0 - ray_org;
        const Vec3vfK R = cross(ray_dir,C);
        const vfloat<K> den = dot(tri_Ng,ray_dir);
        const vfloat<K> absDen = abs(den);
        const vfloat<K> sgnDen = signmsk(den);
        
        /* test against edge p2 p0 */
        const vfloat<K> U = dot(R,tri_e2) ^ sgnDen;
        valid &= U >= 0.0f;
        if (likely(none(valid))) return false;
        
        /* test against edge p0 p1 */
        const vfloat<K> V = dot(R,tri_e1) ^ sgnDen;
        valid &= V >= 0.0f;
        if (likely(none(valid))) return false;
        
        /* test against edge p1 p2 */
        const vfloat<K> W = absDen-U-V;
        valid &= W >= 0.0f;
        if (likely(none(valid))) return false;
        
        /* perform depth test */
        const vfloat<K> T = dot(tri_Ng,C) ^ sgnDen;
        valid &= (T >= absDen*ray_tnear) & (absDen*ray_tfar >= T);
        if (unlikely(none(valid))) return false;
        
        /* perform backface culling */
#if defined(EMBREE_BACKFACE_CULLING)
        valid &= den < vfloat<K>(zero);
        if (unlikely(none(valid))) return false;
#else
        valid &= den != vfloat<K>(zero);
        if (unlikely(none(valid))) return false;
#endif
        
        /* calculate hit information */
        MoellerTrumboreHitK<K> hit(U,V,T,absDen,tri_Ng);
        return epilog(valid,hit);
      }
      
      /*! Intersects K rays with one of M triangles. */
      template<typename Epilog>
      __forceinline vbool<K> intersectK(const vbool<K>& valid0, 
                                        RayK<K>& ray, 
                                        const Vec3<vfloat<K>>& tri_v0, 
                                        const Vec3<vfloat<K>>& tri_v1, 
                                        const Vec3<vfloat<K>>& tri_v2, 
                                        const Epilog& epilog) const
      {
        typedef Vec3<vfloat<K>> Vec3vfK;
        const Vec3vfK e1 = tri_v0-tri_v1;
        const Vec3vfK e2 = tri_v2-tri_v0;
        const Vec3vfK Ng = cross(e1,e2);
        return intersectK(valid0,ray.org,ray.dir,ray.tnear,ray.tfar,tri_v0,e1,e2,Ng,epilog);
      }

      /*! Intersects K rays with one of M triangles. */
      template<typename Epilog>
      __forceinline vbool<K> intersectK(const vbool<K>& valid0, 
                                        RayK<K>& ray, 
                                        const Vec3<vfloat<K>>& tri_v0, 
                                        const Vec3<vfloat<K>>& tri_e1, 
                                        const Vec3<vfloat<K>>& tri_e2, 
                                        const Vec3<vfloat<K>>& tri_Ng, 
                                        const Epilog& epilog) const
      {
        return intersectK(valid0,ray.org,ray.dir,ray.tnear,ray.tfar,tri_v0,tri_e1,tri_e2,tri_Ng,epilog);
      }
      
      /*! Intersect k'th ray from ray packet of size K with M triangles. */
      template<typename Epilog>
        __forceinline bool intersect(RayK<K>& ray, 
                                     size_t k,
                                     const Vec3<vfloat<M>>& tri_v0, 
                                     const Vec3<vfloat<M>>& tri_e1, 
                                     const Vec3<vfloat<M>>& tri_e2, 
                                     const Vec3<vfloat<M>>& tri_Ng,
                                     const Epilog& epilog) const
      {
        /* calculate denominator */
        typedef Vec3<vfloat<M>> Vec3vfM;
        const Vec3vfM O = broadcast<vfloat<M>>(ray.org,k);
        const Vec3vfM D = broadcast<vfloat<M>>(ray.dir,k);
        const Vec3vfM C = Vec3vfM(tri_v0) - O;
        const Vec3vfM R = cross(D,C);
        const vfloat<M> den = dot(Vec3vfM(tri_Ng),D);
        const vfloat<M> absDen = abs(den);
        const vfloat<M> sgnDen = signmsk(den);
        
        /* perform edge tests */
        const vfloat<M> U = dot(R,Vec3vfM(tri_e2)) ^ sgnDen;
        const vfloat<M> V = dot(R,Vec3vfM(tri_e1)) ^ sgnDen;
        
        /* perform backface culling */
#if defined(EMBREE_BACKFACE_CULLING)
        vbool<M> valid = (den < vfloat<M>(zero)) & (U >= 0.0f) & (V >= 0.0f) & (U+V<=absDen);
#else
        vbool<M> valid = (den != vfloat<M>(zero)) & (U >= 0.0f) & (V >= 0.0f) & (U+V<=absDen);
#endif
        if (likely(none(valid))) return false;
        
        /* perform depth test */
        const vfloat<M> T = dot(Vec3vfM(tri_Ng),C) ^ sgnDen;
        valid &= (T > absDen*vfloat<M>(ray.tnear[k])) & (T < absDen*vfloat<M>(ray.tfar[k]));
        if (likely(none(valid))) return false;
        
        /* calculate hit information */
        MoellerTrumboreHitM<M> hit(valid,U,V,T,absDen,tri_Ng);
        return epilog(valid,hit);
      }
      
      template<typename Epilog>
      __forceinline bool intersect(RayK<K>& ray, 
                                    size_t k,
                                    const Vec3<vfloat<M>>& v0, 
                                    const Vec3<vfloat<M>>& v1, 
                                    const Vec3<vfloat<M>>& v2, 
                                    const Epilog& epilog) const
      {
        const Vec3<vfloat<M>> e1 = v0-v1;
        const Vec3<vfloat<M>> e2 = v2-v0;
        const Vec3<vfloat<M>> Ng = cross(e1,e2);
        return intersect(ray,k,v0,e1,e2,Ng,epilog);
      }
    };
  }
}