Time Dependent Structures

GRAPE allows you to express time dependency in your data and thereby to produce animated sequences. There is a time ruler in the manager which lets you change the time interactively. The fundamental idea of the realization of time dependency is to create a class that includes a method "get-object" which can provide your geometry for any given time. One of the already existing classes which provides such a method is the class TimeStep. Its concept is to store a number of objects -- e. g. geometries or numerical data -- and the timevalues they belong to in one dynamic object. By interpolating these keyframe-geometries, GRAPE can provide a geometric object for any given time and as a consequence produce a continuous animation. An instance of the class TimeStep realizes a linked list that contains the keyframe-geometries. If you use adaptive geometries, you let GRAPE know how the geometry has changed by storing two geometries belonging to the same timevalue: One of these keyframe-geometries is used for interpolating with the previous timestep, the other for interpolating with the next timestep. If you want to make use of another concept of time dependency, you can easily implement that. In some cases it might for example make sense to rather calculate the object for a specific time from the data than use stored objects which need a lot of memory. To implement your own concept of time dependency, you only need to implement a class of your own that provides your own method "get-object". Time-dependent objects become part of the object hierarchy with the help of the class TimeScene, a subclass of the class Scene. In addition to an instance of the class Scene, an instance of the class TimeScene contains the current timevalue and a reference to a dynamic object such as an instance of the class TimeStep.