Abstract: When evaluating eye tracking algorithms, a recurring issue is what metric to use and what data to compare against. User studies are informative when considering the entire eye tracking system, however they are often unsatisfactory for evaluating the gaze estimation algorithm in isolation. This is particularly an issue when evaluating a system's component parts, such as pupil detection, pupil-to-gaze mapping or head pose estimation. Instead of user studies, eye tracking algorithms can be evaluated using simulated input video. We describe a computer graphics approach to creating realistic synthetic eye images, using a 3D model of the eye and head and a physically correct rendering technique. By using rendering, we have full control over the parameters of the scene such as the gaze vector or camera position, which allows the calculation of ground truth data, while creating a realistic input for a video-based gaze estimator.