Saving window animations as video

In this recipe,we'll start by drawing a simple animation and learning how to export it to video. We will create a video where pressing any key will start or stop the recording.

Getting ready

You must have Apple's QuickTime installed. Make sure you know where you want your video to be saved, as you'll have to specify its location at the beginning.

It could be anything that is drawn using OpenGl but for this example, we'll create a yellow circle at the center of the window with a changing radius. The radius is calculated by the absolute value of the sine of the elapsed seconds since the application launched. We multiply this value by 200 to scale it up. Now add the following to the draw method:

gl::clear( Color( 0, 0, 0 ) );     
float radius = fabsf( sinf( getElapsedSeconds() ) ) * 200.0f;
Vec2f center = getWindowCenter();
gl::color( Color( 1.0f, 1.0f, 0.0f ) );
gl::drawSolidCircle( center, radius );

How to do it…

We will use the ci::qtime::MovieWriter class to...