Question

I am working on a Qt/GPU/OpenCL code with OpenGL rendering. It performs an animation of a 3D scene and I succeed in rotating this 3D scene with mouse while the animation. But the rotation doesn’t work when I do a pause of the animation, i.e when the 3D scene is “fixed”.

here’s the two functions for the rotation with mouse :

void GLWidget::mousePressEvent(QMouseEvent *event)
 {
     lastPos = event->pos();
 }

 void GLWidget::mouseMoveEvent(QMouseEvent *event)
 {
     float dx = (event->y() - lastPos.y()) / 10.0f;
     float dy = (event->x() - lastPos.x()) / 10.0f;
     float dz = 0.0f;
     float angle = sqrtf((event->x() - lastPos.x()) + (event->y() - lastPos.y()));

     if (event->buttons() & Qt::LeftButton) {
        angle = sqrtf(dx*dx + dy*dy);
        glRotatef(0.1*angle, dx, dy, dz);
       }
 }

When the animation is on “pause”, I would like to be able to rotate the fixed scene and when I push the “restart” button, I would like the animation restarts with the last modified image done by the rotation of the scene.

So, this should be, before to do “pause”, like a snapshot of the last animation, then the possiblity to rotate, and finally, restart the animation from the last 3D rotated scene.

Here’s my main display function “processCurrent()” called by a QTimer and where "draw()" contains OpenGL functions and animation is set to false when I do a pause :

 void GLWidget::processCurrent()
{

 if (Galaxy->isFirstLaunch)
    {
    draw();
    printStats();
    //Calling kernel for calculatig subsequent positions
    Galaxy->runCLKernels();
    Galaxy->isFirstLaunch = false;
    glFlush();
    swapBuffers();
    }

 if (animation)
    {
    clWaitForEvents(1, &Galaxy->glEvent);
    draw();
    printStats();
    //Calling kernel for calculatig subsequent positions
    Galaxy->runCLKernels();
    glFlush();
    swapBuffers();
   }

}

Could you explain me why this rotation doesn’t work with a fixed scene ?

Answer 1

you still need to draw the scene, if draw() only does draw operations and no animation operations and runCLKernels does animation this should work:

if(animation)
{
    //same as before...
}
else
{
    // I don't know whether or not you would still call WaitForEvents...
    draw();
    printStats();
    // Do NOT calculate subsequent positions, just use what was calculated last time.
    glFlush();
    swapBuffers();
}