Real-time Visualization versus Animation

Technically, when you play an interactive game with intense graphics or watch an animation feature, every scene or image you see on the screen at any given moment must be drawn or rendered. It takes time for the computer to draw each scene. So the more complex or graphic-intense the scene, the longer the drawing time is required. 

Animation. When you watch an animated feature, it is made up of a 3D environment represented by thousands of complex scenes or sequenced frames of that environment that must be rendered or drawn. This rendering process takes a lot of time to draw every image (sometimes up to 20 minutes per frame depending on (1) the complexity of scene and (2) the power of the computer(s) doing the rendering). The animator, however, has already decided the sequence of the frames and can pre-render them on powerful computers over a period of days. Since these animations stress realism and special effects and they have time to pre-render the frames, they typically have highly-complex scenes with lots of geometric detail, lighting, shading. 

Real-time. A 'Real-time' experience refers to a live rendering or drawing time of typically 30 frames per second, which is close to simulating our experience in real life. Scenes for real-time need to be rendered at such speeds because emphasis is placed on enabling an interactive, dynamic experience for the user.  The sequence of the scenes being drawn is not determined until the user actually interacts with the environment. Every time the user moves the mouse to change his/ her perspective ever so slightly, a new scene must be rendered. In order to simulate a real-time experience, each frame must be drawn as quickly as possible so that movement around the place is smooth and realistic. Such fast rendering times are achieved by less complex geometric scenes and the use of photographic imagery.  For instance, instead of building every mullion of a window on a building façade, the detail for that window can be represented more optimally by the use of photograph of that window pasted onto the model.

Real-time modeling uses simple geometry and textures View movie with:  ™Quicktime or ™Windows Media Player     Screen capture of live fly-thru with switching of alternatives.

Summary

Animations are pre-recorded so they can be rendered overnight and then played back on a path through the model.  It is, therefore, a passive experience for a user, much like watching a movie. A real-time environment is an active experience for the user where scenes are rendered "on the fly" so the user can move and look freely within the model. In general, planning support systems tend to favor real-time packages over animation packages because of their freedom of movement, ease-of-use, more robust connections to mapping data, and ability to generate alternative scenarios quickly.