/home/master/UCL/VisualizationLibrary/src/vlGraphics/RayIntersector.cpp

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/*  Visualization Library                                                             */
/*  http://visualizationlibrary.org                                                   */
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#include <vlGraphics/RayIntersector.hpp>
#include <vlGraphics/SceneManager.hpp>

using namespace vl;

//-----------------------------------------------------------------------------
void RayIntersector::intersect(const Ray& ray, SceneManager* scene_manager)
{
  actors()->clear();
  scene_manager->extractActors( *actors() );
  setRay(ray);
  intersect();
}
//-----------------------------------------------------------------------------
void RayIntersector::intersect()
{
  mIntersections.clear();
  for(int i=0; i<actors()->size(); ++i)
  {
    if (!frustum().cull(actors()->at(i)->boundingBox()))
    {
      intersect(actors()->at(i));
    }
  }

  std::sort( mIntersections.begin(), mIntersections.end(), sorter );
}
//-----------------------------------------------------------------------------
void RayIntersector::intersect(Actor* act)
{
  Geometry* geom = cast<Geometry>(act->lod(0));
  if (geom)
    intersectGeometry(act, geom);
}
//-----------------------------------------------------------------------------
void RayIntersector::intersectGeometry(Actor* act, Geometry* geom)
{
  ArrayAbstract* posarr = geom->vertexArray() ? geom->vertexArray() : geom->vertexAttribArray(vl::VA_Position) ? geom->vertexAttribArray(vl::VA_Position)->data() : NULL;
  if (posarr)
  {
    mat4 matrix = act->transform() ? act->transform()->worldMatrix() : mat4();
    for(int i=0; i<geom->drawCalls()->size(); ++i)
    {
      DrawCall* prim = geom->drawCalls()->at(i);
      int itri = 0;
      for(TriangleIterator trit = prim->triangleIterator(); trit.hasNext(); trit.next(), ++itri)
      {
        int ia = trit.a();
        int ib = trit.b();
        int ic = trit.c();
        vec3 a = posarr->getAsVec3(ia);
        vec3 b = posarr->getAsVec3(ib);
        vec3 c = posarr->getAsVec3(ic);
        if (act->transform())
        {
          a = matrix * a;
          b = matrix * b;
          c = matrix * c;
        }
        intersectTriangle(a, b, c, ia, ib, ic, act, geom, prim, itri);
      }
    }
  }
}
//-----------------------------------------------------------------------------
template<class T>
void RayIntersector::intersectTriangle(const T& a, const T& b, const T& c, int ia, int ib, int ic, Actor* act, Geometry* geom, DrawCall* prim, int tri_idx)
{
  T v1 = b-a;
  T v2 = c-a;
  T n = cross(v1,v2).normalize();
  real det = (real)dot(n,(T)ray().direction());
  if(det == 0)
    return;
  real t = (real)dot(n, a-(T)ray().origin()) / det;
  if (t<0)
    return;
  vec3  rp = ray().origin() + ray().direction() * t;
  T fp = (T)rp;
  T pts[] = { a, b, c, a };
  for(int i=0; i<3; ++i)
  {
    T bi_norm = -cross(pts[i+1]-pts[i],n).normalize();
    if (dot(fp-pts[i],bi_norm) < 0)
      return;
  }
  ref<RayIntersectionGeometry> record = new vl::RayIntersectionGeometry;
  record->setIntersectionPoint( rp );
  record->setTriangleIndex(tri_idx);
  record->setTriangle(ia, ib, ic);
  record->setActor(act);
  record->setGeometry(geom);
  record->setPrimitives(prim);
  record->setDistance( t );
  mIntersections.push_back(record);
}
//-----------------------------------------------------------------------------