Motion blur

Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation.

In such an image, any object moving with respect to the camera will look blurred or smeared along the direction of relative motion.

In this case, even with long exposure times, the moving objects will appear sharper while the background will become more blurred, with the resulting image conveying a sense of movement and speed.

Without this simulated effect each frame shows a perfect instant in time (analogous to a camera with an infinitely fast shutter), with zero motion blur.

Some of the better-known games that utilise this are the recent Need for Speed titles, Unreal Tournament III, The Legend of Zelda: Majora's Mask, among many others.

Classic "motion blur" effects prior to modern per-pixel shading pipelines often simply drew successive frames on top of each other with slight transparency, which is strictly speaking a form of video feedback.

In pre-rendered computer animation, such as CGI movies, realistic motion blur can be drawn because the renderer has more time to draw each frame.

Thus most computer animation systems will incorrectly place an object on a four frame trip along a path at 0%, 0.33%, 0.66%, and 1.0% and when called upon to render motion blur will have to cut one or more frames short, or look beyond the boundaries of the animation, compromises that real cameras don't do and synthetic cameras needn't do.

Many graphical software products (e.g. Adobe Photoshop or GIMP) offer simple motion blur filters.

However, for advanced motion blur filtering including curves or non-uniform speed adjustment, specialized software products (e.g. VirtualRig Studio) are necessary.

To cope with this, humans generally alternate between saccades (quick eye movements) and fixation (focusing on a single point).