main.cpp Example File

simpleoffscreen/main.cpp

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  #include <q3dsruntimeglobal.h>
  #include <Q3DSSurfaceViewer>
  #include <Q3DSPresentation>
  #include <QGuiApplication>
  #include <QOffscreenSurface>
  #include <QOpenGLContext>
  #include <QOpenGLFramebufferObject>
  #include <QThread>

  int main(int argc, char *argv[])
  {
      QGuiApplication app(argc, argv);
      QSurfaceFormat::setDefaultFormat(Q3DS::surfaceFormat());

      QOpenGLContext context;
      if (!context.create())
          qFatal("Failed to create OpenGL context");

      // Must have a "surface". Depending on the platform this may be a small
      // window, pbuffer surface, or even nothing (in case surfaceless contexts are
      // supported) under the hood.
      QOffscreenSurface surface;
      surface.create();

      if (!context.makeCurrent(&surface))
          qFatal("makeCurrent failed");

      const QSize size(1280, 800);
      QOpenGLFramebufferObject fbo(size, QOpenGLFramebufferObject::CombinedDepthStencil);

      Q3DSSurfaceViewer viewer;
      viewer.presentation()->setSource(QUrl(QStringLiteral("qrc:/barrel.uip")));

      // Will call update() manually when a new frame is wanted.
      viewer.setUpdateInterval(-1);

      // Automatic sizing must be turned off.
      viewer.setAutoSize(false);

      // Provide the render target size instead.
      viewer.setSize(size);

      if (!viewer.create(&surface, &context, fbo.handle()))
          qFatal("Initialization failed");

      // Render a few frames, read them back, and save into png files.
      for (int frame = 1; frame <= 20; ++frame) {
          // Render the next frame.
          viewer.update();

          // Write it to a file.
          context.makeCurrent(&surface);
          const QString fn = QString(QLatin1String("output_%1.png")).arg(frame);
          fbo.toImage().save(fn);

          qDebug("Rendered and saved frame %d to %s", frame, qPrintable(fn));

          // Keep events delivered on this (main) thread.
          QCoreApplication::processEvents();

          // ### hack until QT3DS-1041 is in place
          QThread::msleep(10);
      }

      // Now one could do the following to generate a 60 fps video from these frames:
      //   ffmpeg -r 60 -f image2 -s 1280x800 -i output_%d.png -vcodec libx264 -crf 25 -pix_fmt yuv420p output.mp4

      // ### this should not be needed. Qt3D should be able to shut down without it.
      QGuiApplication::processEvents();

      return 0;
  }