Spiegel Movie Glossary

Movie

The term movie is used in several different places in Spiegel. A movie can be one of two things: In the first sense, a movie refers to a saved file that contains the streams associated with a flythrough. By saving the streams and keyframes, the user can re-run a visualization whenever necessary. The movie file is a simple text file ending in .movie. These movie files are created, loaded, and saved using the "Flythrough" tab, which is discussed later. The second type of movie are standard video files such as .mov and .avi. Spiegel can use a .movie file to generate series of images, which can be made into either a compressed QuickTime^? movie, or a raw AVI movie. This is done through the "Generate Movie" tab.

Flythrough

The term flythrough indicates the path of a camera through a visualization. Using the path editor, the path a camera takes can be defined. A flythrough also encompasses the simulation time during the flythrough path.

Stream

A stream is an item of data that changes over time, producing a "stream" of values. When this document refers to a stream, just think of it as a container of data that controls a particular thing. For example, there is a CameraLocation^? stream, whose purpose is to control the location of a camera over time. Each stream has an associated data type, determining what sort of data it produces.

Keyframe

All streams are made up of keyframes. A keyframe is a reference point in time for the stream. If the stream is a camera location stream, a keyframe will contain a time value as well as the X, Y, and Z coordinates of the camera at that time.

Stream Value Types

There are three stream types - double, vector, and string. A camera location stream uses a vector type, since all locations must consist of three coordinates. A simulation time stream uses a double type, since time is maintained as a floating-point value.

Interpolators

An interpolator is responsible for computing the value of a stream using the stream's keyframes and the current time value. The interpolators work as follows:

Constant

The value remains constant until the next keyframe.

Linear

The value changes in a linear fashion between keyframes, such as in simulation time streams, where time is usually expected to move linearly.

TCB

Short for Tension-Continuity-Bias, the three parameters used to control it, this interpolator uses Kochanek-Bartels splines to generate a smooth spline curve with the keyframe's data as anchor points. This is typically used for camera movement.

Command

Associated with Command streams for interpreting commands

Command

Spiegel is controlled by commands that tell it what to do, and movies can specify commands to be executed at various times.

-- AndrewRader^?