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# The manipulatedFrame example

A `ManipulatedFrame` can be moved with the mouse in the scene.

A ManipulatedFrame converts mouse gestures into Frame displacements. Adding two lines of code will allow you to move any object of your scene using the mouse. The button bindings of the ManipulatedFrame are the same as for the camera. Spinning is possible.

The frame is drawn at its position using a `glMultMatrix` of the frame associated matrix(). This matrix is changed when the mouse moves, thus changing the position of the frame.

## manipulatedFrame.h

    #include <QGLViewer/qglviewer.h>

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

## manipulatedFrame.cpp

    #include "manipulatedFrame.h"
    #include <math.h>

    using namespace qglviewer;
    using namespace std;

    static void drawSpiral()
    {
      const float 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 = .5;
          const float up = sqrt(1.0-nor*nor);
          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();
    }

    void Viewer::init()
    {
      // Swap the CAMERA and FRAME state keys (NoButton and Control)
      // Save CAMERA binding first. See setHandlerKeyboardModifiers() documentation.
    #if QT_VERSION < 0x040000
      setHandlerKeyboardModifiers(QGLViewer::CAMERA, Qt::AltButton);
      setHandlerKeyboardModifiers(QGLViewer::FRAME,  Qt::NoButton);
      setHandlerKeyboardModifiers(QGLViewer::CAMERA, Qt::ControlButton);
    #else
      setHandlerKeyboardModifiers(QGLViewer::CAMERA, Qt::AltModifier);
      setHandlerKeyboardModifiers(QGLViewer::FRAME,  Qt::NoModifier);
      setHandlerKeyboardModifiers(QGLViewer::CAMERA, Qt::ControlModifier);
    #endif

    #ifdef GL_RESCALE_NORMAL  // OpenGL 1.2 Only...
      glEnable(GL_RESCALE_NORMAL);
    #endif

      // Add a manipulated frame to the viewer.
      // If you are not "using namespace qglqglviewer", you need
      // to specify: new qglviewer::ManipulatedFrame().
      setManipulatedFrame(new ManipulatedFrame());

      help();
      restoreStateFromFile();

      // Make world axis visible
      setAxisIsDrawn();
    }

    void Viewer::draw()
    {
      // Here we are in the world coordinate system.
      // Draw your scene here.

      // Save the current model view matrix (not needed here in fact)
      glPushMatrix();

      // Multiply matrix to get in the frame coordinate system.
      glMultMatrixd(manipulatedFrame()->matrix());

      // Scale down the drawings
      glScalef(0.3f, 0.3f, 0.3f);

      // Draw an axis using the QGLViewer static function
      drawAxis();

      // Draws a frame-related spiral.
      drawSpiral();

      // Restore the original (world) coordinate system
      glPopMatrix();
    }

    QString Viewer::helpString() const
    {
      QString text("<h2>M a n i p u l a t e d F r a m e</h2>");
      text += "A <i>ManipulatedFrame</i> converts mouse gestures into <i>Frame</i> displacements. ";
      text += "In this example, such an object defines the position of the spiral that can hence be manipulated.<br><br>";
      text += "Adding two lines of code will then allow you to move the objects of ";
      text += "your scene using the mouse. The button bindings of the <i>ManipulatedFrame</i> ";
      text += "are the same than for the camera. Spinning is possible.<br><br>";
      text += "Default key bindings have been changed in this example : press <b>Control</b> ";
      text += "while moving the mouse to move the camera instead of the ManipulatedFrame.";
      return text;
    }

## main.cpp

    #include "manipulatedFrame.h"
    #include <qapplication.h>

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

      Viewer viewer;

    #if QT_VERSION < 0x040000
      application.setMainWidget(&viewer);
    #else
      viewer.setWindowTitle("manipulatedFrame");
    #endif

      viewer.show();

      return application.exec();
    }

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Last modified on Sunday, February 28, 2010.