TrackballNode.cc

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\*===========================================================================*/




//=============================================================================
//
//  CLASS TrackballNode - IMPLEMENTATION
//
//=============================================================================


//== INCLUDES =================================================================


#include "TrackballNode.hh"


//== NAMESPACES ===============================================================


namespace ACG {
namespace SceneGraph {


//== IMPLEMENTATION ========================================================== 


void
TrackballNode::draw(GLState& /* _state */ , const DrawModes::DrawMode& /* _drawMode */ )
{
  // draw the trackball
  if (drawTrackball_) 
  {
    ACG::GLState::disable(GL_LIGHTING);
    ACG::GLState::shadeModel( GL_FLAT );
    glPushMatrix();
    glTranslatef(center()[0], center()[1], center()[2]);
    glutWireSphere(radius_, 20, 20);
    glPopMatrix();
  }


  // draw the coord axes
  if (drawAxes_)
  {
    // store original settings
    GLfloat backupColor[4], backupLineWidth;
    glGetFloatv(GL_CURRENT_COLOR, backupColor);
    glGetFloatv(GL_LINE_WIDTH, &backupLineWidth);
    
    ACG::GLState::disable(GL_LIGHTING);
    ACG::GLState::shadeModel( GL_FLAT );
    glLineWidth(3.0);

    glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_LINES);
    glVertex(center());
    glVertex(center() + radius_*xAxis_);
    glEnd();

    glColor3f(0.0, 1.0, 0.0);
    glBegin(GL_LINES);
    glVertex(center());
    glVertex(center() + radius_*yAxis_);
    glEnd();

    glColor3f(0.0, 0.0, 1.0);
    glBegin(GL_LINES);
    glVertex(center());
    glVertex(center() + radius_*zAxis_);
    glEnd();

    // restore original settings
    glColor4fv(backupColor);
    glLineWidth(backupLineWidth);
  }
}


//----------------------------------------------------------------------------


void
TrackballNode::mouseEvent(GLState& _state, QMouseEvent* _event)
{
  Vec3d         oldPoint3D;
  Vec2i         newPoint2D(_event->pos().x(), _event->pos().y());
  Vec3d         newPoint3D;


  switch (_event->type())
  {
    case QEvent::MouseButtonPress:
    {
      break;
    }


    case QEvent::MouseButtonDblClick:
    {
      if (mapToSphere(_state, oldPoint2D_, oldPoint3D))
      {
        // toggle drawTrackball_
        if (_event->button() == Qt::LeftButton)
          drawTrackball_ = !drawTrackball_;

        // toggle drawAxes_
        if (_event->button() == Qt::MidButton)
          drawAxes_ = !drawAxes_;
      }
      break;
    }
    
    
    case QEvent::MouseMove:
    {
      bool hit0 = mapToSphere(_state, newPoint2D, newPoint3D);
      bool hit1 = mapToSphere(_state, oldPoint2D_, oldPoint3D);

      if (hit0 && hit1)
      {

        // scaling
        if ((_event->button() & Qt::LeftButton) &&
            (_event->button() & Qt::MidButton))
        {
          double s = 1.0 + ((double) (newPoint2D[1] - oldPoint2D_[1]) /
                           (double) _state.viewport_height());
          scale(s);
        }


        // translation
        else if (_event->button() & Qt::MidButton)
        {
          double value_x = (radius_ * ((newPoint2D[0] - oldPoint2D_[0])) 
                           * 2.0 / (double) _state.viewport_width());
          
          double value_y = (radius_ * ((newPoint2D[1] - oldPoint2D_[1]))
                           * 2.0 / (double) _state.viewport_height());
          
          
          /* need inverse transposed matrix in order to
             transform direction vectors */
          GLMatrixd m = inverse_matrix();
          m.transpose();


          Vec3d dx, dy;

          // axis aligned
          if (drawAxes_)
          {
            dx = m.transform_point(xAxis_);
            dy = m.transform_point(yAxis_);
          }

          // screen space translation
          else 
          {
            dx = m.transform_vector(_state.right());
            dy = m.transform_vector(_state.up());
          }
          
          dx.normalize();
          dy.normalize();
          translate(value_x*dx - value_y*dy);
        }
      


        // rotation
        else if (_event->button() & Qt::LeftButton) 
        {
          Vec3d axis = oldPoint3D % newPoint3D; 
          double cos_angle = ( oldPoint3D | newPoint3D );

          
          if (fabs(cos_angle) < 1.0)
          {
            // rotate coord axes
            if (_event->modifiers() & Qt::AltModifier)
            {
              GLMatrixd mat;
              
              mat.identity();
              mat.rotate(acos(cos_angle)*180.0/M_PI, axis);
              
              /* transform_point works since only 
                 rotations and no translations are
                 involved */
              xAxis_ = mat.transform_point(xAxis_);
              yAxis_ = mat.transform_point(yAxis_);
              zAxis_ = mat.transform_point(zAxis_);
            }
            
            // normal rotation
            else  rotate(acos(cos_angle)*180.0/M_PI, axis);
          }
        }
      }


      break;
    }

    default: // avoid warning
      break;
  }


  // store 2D point
  oldPoint2D_ = newPoint2D;
}


//----------------------------------------------------------------------------


bool
TrackballNode::mapToSphere( GLState& _state,
                            const Vec2i& _v2, 
                            Vec3d& _v3 )
{
  // Qt -> GL coordinate systems
  unsigned int x = _v2[0];
  unsigned int y = _state.context_height() - _v2[1];


  // get ray from eye through pixel (trackball coords)
  Vec3d origin, direction;
  _state.viewing_ray(x, y, origin, direction);


  // translate and scale trackball to unit sphere
  origin -= center();
  origin /= radius_;


  // calc sphere-ray intersection
  // (sphere is centered at origin, has radius 1)
  double a = direction.sqrnorm(),
        b = 2.0 * (origin | direction),
        c = origin.sqrnorm() - 1.0,
        d = b*b - 4.0*a*c,
        t;

  if      (d <  0.0)  return false;
  else if (d == 0.0)  t = -b / (2.0*a);
  else 
  { 
    // t1 = (-b - sqrt(d)) / (2.0*a),  t2 = (-b + sqrt(d)) / (2.0*a)
    a = 1.0 / (2.0*a);
    d = sqrt(d);
    double t1 = (-b - d) * a;
    double t2 = (-b + d) * a;
    t = (t1 < t2) ? t1 : t2;
  }

  _v3 = origin + direction*t;
  
  return true;
}


//=============================================================================
} // namespace SceneGraph
} // namespace ACG
//=============================================================================