frame_transform.cpp

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/*****************************************************************************
** Includes
*****************************************************************************/

#include <qapplication.h>
#include <QGLViewer/qglviewer.h>

using namespace qglviewer;

/*****************************************************************************
** Frame Transform
*****************************************************************************/

class FrameTransform : public QGLViewer
{
protected :
  virtual void draw();
  virtual void init();
  virtual QString helpString() const;
};

/*****************************************************************************
 ** FrameTransform
 *****************************************************************************/

void FrameTransform::init()
{
  restoreStateFromFile();

  setSceneRadius(1.5);
  showEntireScene();
  setAxisIsDrawn();
  glDisable(GL_LIGHTING);

  help();
}

void FrameTransform::draw()
{
  // Draws line sets (red, green, blue) with different origins, but with a common
  // end point, located on a circle in the XY plane.
  const float nbLines = 50.0;

  glBegin(GL_LINES);

  for (float i=0; i<nbLines; ++i)
    {
      float angle = 2.0*M_PI*i/nbLines;

      glColor3f(0.8f, 0.2f, 0.2f);
      // These lines will never be seen as they are always aligned with the viewing direction.
      glVertex3fv(camera()->position());
      glVertex3f (cos(angle), sin(angle), 0.0);

      glColor3f(0.2f, 0.8f, 0.2f);
      // World Coordinates are infered from the camera, and seem to be immobile in the screen.
      glVertex3fv(camera()->worldCoordinatesOf(Vec(.3*cos(angle), .3*sin(angle), -2.0)));
      glVertex3f (cos(angle), sin(angle), 0.0);

      glColor3f(0.2f, 0.2f, 0.8f);
      // These lines are defined in the world coordinate system and will move with the camera.
      glVertex3f(1.5*cos(angle), 1.5*sin(angle), -1.0);
      glVertex3f(cos(angle), sin(angle), 0.0);
    }
  glEnd();

  // Here, the camera position in world coord. system  is camera()->position().
  // The world origin position in camera frame can be obtained from camera()->cameraCoordinatesOf(Vec(0.0, 0.0, 0.0))
}

QString FrameTransform::helpString() const
{
  QString text("<h2>F r a m e T r a n s f o r m</h2>");
  text += "This example illustrates how easy it is to switch between the camera and ";
  text += "the world coordinate systems using the <i>camera()->cameraCoordinatesOf()</i> ";
  text += "and <i>camera::worldCoordinatesOf()</i> functions.<br><br>";
  text += "You can create your own hierarchy of local coordinates systems and each of ";
  text += "them can be manipulated with the mouse (see the <i>manipulatedFrame</i> and <i>luxo</i> examples). ";
  text += "Standard functions allow you to convert from any local frame to any other, ";
  text += "the world/camera conversion presented here simply being an illustration.<br><br>";
  text += "See <i>examples/frameTransform.html</i> for an explanation of the meaning of these weird lines.";
  return text;
}

/*****************************************************************************
** Main
*****************************************************************************/

int main(int argc, char** argv)
{
  QApplication application(argc,argv);

  FrameTransform viewer;

  viewer.setWindowTitle("keyFrames");

  viewer.show();

  return application.exec();
}