The animation example

animation

The animate() function illustrated by a water particle simulation.

When animation is activated (the Return key toggles animation), the animate() and then the draw() functions are called in an infinite loop.

You can tune the frequency of your animation (default is 25Hz) using setAnimationInterval(). The frame rate will then be fixed, provided that your animation loop function is fast enough.

animation.h

#include <QGLViewer/qglviewer.h>

class Particle {
public:
  Particle();

  void init();
  void draw();
  void animate();

private:
  qglviewer::Vec speed_, pos_;
  int age_, ageMax_;
};

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

private:
  int nbPart_;
  Particle *particle_;
};

animation.cpp

#include "animation.h"
#include <math.h>
#include <stdlib.h> // RAND_MAX

using namespace qglviewer;
using namespace std;

///////////////////////   V i e w e r  ///////////////////////
void Viewer::init() {
  restoreStateFromFile();
  glDisable(GL_LIGHTING);
  nbPart_ = 2000;
  particle_ = new Particle[nbPart_];
  glPointSize(3.0);
  setGridIsDrawn();
  help();
  startAnimation();
}

void Viewer::draw() {
  glBegin(GL_POINTS);
  for (int i = 0; i < nbPart_; i++)
    particle_[i].draw();
  glEnd();
}

void Viewer::animate() {
  for (int i = 0; i < nbPart_; i++)
    particle_[i].animate();
}

QString Viewer::helpString() const {
  QString text("<h2>A n i m a t i o n</h2>");
  text += "Use the <i>animate()</i> function to implement the animation part "
          "of your ";
  text += "application. Once the animation is started, <i>animate()</i> and "
          "<i>draw()</i> ";
  text += "are called in an infinite loop, at a frequency that can be "
          "fixed.<br><br>";
  text += "Press <b>Return</b> to start/stop the animation.";
  return text;
}

///////////////////////   P a r t i c l e   ///////////////////////////////

Particle::Particle() { init(); }

void Particle::animate() {
  speed_.z -= 0.05f;
  pos_ += 0.1f * speed_;

  if (pos_.z < 0.0) {
    speed_.z = -0.8 * speed_.z;
    pos_.z = 0.0;
  }

  if (++age_ == ageMax_)
    init();
}

void Particle::draw() {
  glColor3f(age_ / (float)ageMax_, age_ / (float)ageMax_, 1.0);
  glVertex3fv(pos_);
}

void Particle::init() {
  pos_ = Vec(0.0, 0.0, 0.0);
  float angle = 2.0 * M_PI * rand() / RAND_MAX;
  float norm = 0.04 * rand() / RAND_MAX;
  speed_ = Vec(norm * cos(angle), norm * sin(angle),
               rand() / static_cast<float>(RAND_MAX));
  age_ = 0;
  ageMax_ = 50 + static_cast<int>(100.0 * rand() / RAND_MAX);
}

main.cpp

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

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

  Viewer viewer;

  viewer.setWindowTitle("animation");

  viewer.show();

  return application.exec();
}

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