thumbnail.cpp

Go to the documentation of this file.

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

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

/*****************************************************************************
** Interface
*****************************************************************************/

class Viewer : public QGLViewer
{
protected :
  virtual void draw();
  virtual void postDraw();
  virtual void init();
  virtual QString helpString() const;
  virtual void keyPressEvent(QKeyEvent *e);

  void drawThumbnail();
  void drawSpiral(bool thumb);

private :
  bool thumbnail_;
};

/*****************************************************************************
 ** Implementation
 *****************************************************************************/

using namespace std;

void Viewer::draw()
{
  drawSpiral(false);
}

// Draws a spiral. If thumb is true, the spiral is simplified and drawns in wireframe.
void Viewer::drawSpiral(bool thumb)
{
  float nbSteps;
  if (thumb)
    {
      nbSteps = 50.0;
      glColor3f(1.0, 1.0 ,1.0);
    }
  else
    nbSteps = 200.0;


  glBegin(GL_QUAD_STRIP);
  for (float i=0; i<nbSteps; ++i)
    {
      float ratio = i/nbSteps;
      float angle = 21.0*ratio;
      float c = cos(angle);
      float s = sin(angle);
      float r1 = 1.0 - 0.8*ratio;
      float r2 = 0.8 - 0.8*ratio;
      float alt = ratio - 0.5;
      const float nor = 0.5;
      const float up = sqrt(1.0-nor*nor);
      if (!thumb)
            glColor3f(1.0-ratio, 0.2f , ratio);
      glNormal3f(nor*c, up, nor*s);
      glVertex3f(r1*c, alt, r1*s);
      glVertex3f(r2*c, alt+0.05, r2*s);
    }
  glEnd();
}

// Manages the thumbnail display.
void Viewer::drawThumbnail()
{
  if (thumbnail_)
    {
      int viewport[4];
      int scissor[4];

      // The viewport and the scissor are changed to fit the lower left
      // corner. Original values are saved.
      glGetIntegerv(GL_VIEWPORT,viewport);
      glGetIntegerv(GL_SCISSOR_BOX,scissor);

      glViewport(0,0,width()/2,height()/2);
      glScissor(0,0,width()/2,height()/2);

      // The Z-buffer is cleared to make the thumbnail appear over the
      // original image.
      glClear(GL_DEPTH_BUFFER_BIT);

      // Here starts the drawing, with specific GL flags
      glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
      glDisable(GL_LIGHTING);
      drawSpiral(true);
      glEnable(GL_LIGHTING);
      glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
      // Here ends the drawing. OpenGL state is restored.

      // The viewport and the scissor are restored.
      glScissor(scissor[0],scissor[1],scissor[2],scissor[3]);
      glViewport(viewport[0],viewport[1],viewport[2],viewport[3]);
    }
}
// The thumbnail has to be drawn at the very end to allow a correct
// display of the visual hints (axes, grid, etc).
void Viewer::postDraw()
{
  QGLViewer::postDraw();
  drawThumbnail();
}

void Viewer::keyPressEvent(QKeyEvent *e)
{
  switch (e->key())
    {
    case Qt::Key_T : thumbnail_ = !thumbnail_; updateGL(); break;
    default        : QGLViewer::keyPressEvent(e);
    }
}
void Viewer::init()
{
  // Restore previous viewer state.
  restoreStateFromFile();

  help();

  thumbnail_ = true;

  setKeyDescription(Qt::Key_T, "Toggles thumbnail display");
}

QString Viewer::helpString() const
{
  QString text("<h2>T h u m b n a i l</h2>");
  text += "A thumbnailed view of the scene is displayed in the lower left corner.<br><br>";
  text += "Such display may be useful for illustration (e.g. to show the data structure) or to debug your ";
  text += "application. It uses <code>glScissor</code> and <code>glViewport</code> to restrict the display area.<br><br>";
  text += "Press <b>T</b> to toggle the thumbnail display";
  return text;
}

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

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

  Viewer viewer;

  viewer.setWindowTitle("thumbnail");

  viewer.show();

  return application.exec();
}