Frustum.cpp

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#include "Frustum.h"

Frustum::Frustum( FrustumInformation frustum ) {
  this->frustum = frustum;
}

Frustum::~Frustum( void ) {
}


void Frustum::setFrustumInformation( FrustumInformation frustum ) {
  this->frustum = frustum;
}


void Frustum::update( CameraObject *camera ) {

  // calculate positions of far plane edges
  Vector3 farCenter = camera->getPos() + camera->getView()  * frustum.farDist;
  farTopLeft= farCenter + (camera->getUp()  * frustum.farHeight*0.5) - (camera->getRight()  * frustum.farWidth*0.5);
  farTopRight= farCenter + (camera->getUp()  * frustum.farHeight*0.5) + (camera->getRight()  * frustum.farWidth*0.5);
  farBottomLeft= farCenter - (camera->getUp()  * frustum.farHeight*0.5) - (camera->getRight()  * frustum.farWidth*0.5);
  farBottomRight = farCenter - (camera->getUp()  * frustum.farHeight*0.5) + (camera->getRight()  * frustum.farWidth*0.5);

  // calculate positions of near plane edges
  Vector3 nearCenter = camera->getPos() + camera->getView()  * frustum.nearDist;
  nearTopLeft= nearCenter + (camera->getUp()  * frustum.nearHeight*0.5) - (camera->getRight()  * frustum.nearWidth*0.5);
  nearTopRight= nearCenter + (camera->getUp()  * frustum.nearHeight*0.5) + (camera->getRight()  * frustum.nearWidth*0.5);
  nearBottomLeft= nearCenter - (camera->getUp()  * frustum.nearHeight*0.5) - (camera->getRight()  * frustum.nearWidth*0.5);
  nearBottomRight = nearCenter - (camera->getUp()  * frustum.nearHeight*0.5) + (camera->getRight()  * frustum.nearWidth*0.5);

  // now compute the six planes bounding the frustum. the points are given in counter clockwise
  // order so that all normals point inside the frustum. that will us easyly allow to check if a point is
  // inside the frustum
  planes[topPlane].setPlane( nearTopRight, nearTopLeft, farTopLeft );
  planes[bottomPlane].setPlane( nearBottomLeft, nearBottomRight, farBottomRight );
  planes[leftPlane].setPlane( nearTopLeft, nearBottomRight, farBottomLeft );
  planes[rightPlane].setPlane( nearBottomRight, nearTopRight, farBottomRight );
  planes[nearPlane].setPlane( nearTopLeft, nearTopRight, nearBottomRight );
  planes[farPlane].setPlane( farTopRight, farTopLeft, farBottomLeft );
}


CullingLocation Frustum::isPointInFrustum( const Vector3 &p ) {
  for(int i=0; i < 6; i++) {
    if (planes[i].distance(p) < 0)
      return outside;
  }
  return inside;
}


CullingLocation Frustum::isSphereInFrustum( const Vector3 &p, float radius ) {
  float distance;
  CullingLocation location = inside;

  for( int i=0; i < 6; i++ ) {
    distance = planes[i].distance( p );
    if( distance < -radius )
      return outside;
    else if( distance < radius )
      location = intersect;               // could be outside of another plane!
  }
  return location;
}


bool Frustum::isInUpperHalf( const Vector3 &p ) {
  float dist1 = planes[topPlane].distance( p );
  float dist2 = planes[bottomPlane].distance( p );
  if( dist1 < 0 )
    return false;
  if( dist1 < dist2 )
    return true;
  else
    return false;
}


bool Frustum::isInRightHalf( const Vector3 &p ) {
  float dist1 = planes[rightPlane].distance( p );
  float dist2 = planes[leftPlane].distance( p );
  if( dist1 < 0 )
    return false;
  if( dist1 < dist2 )
    return true;
  else
    return false;
}


float Frustum::getFrustumWidth( float dist ) {
  if( dist < frustum.nearDist || dist > frustum.farDist )
    return 0;
  
  float val = getFrustumHeight( dist ) * frustum.aspect;
  return val;
}



float Frustum::getFrustumHeight( float dist ) {
  if( dist < frustum.nearDist || dist > frustum.farDist )
    return 0;

  float val = 2 * tan( frustum.fov * ANGLE2DEG * 0.5 ) * dist;
  return val;
}