2.1 Design time

One of the important differences between a software component and a (software) object is that a component should have a design time interface and an object should not necessarily have one. Between the development and the actual use, a design phase is foreseen, in which components can be customised and connected to each other. Not in all applications it is clear what should be done in this phase and who should do it.

In the process of building animations, this is much clearer. The software developer builds the system to perform the animations. The end user views the animations and interacts with it. In between is the designer of the animation. He likes to think about his animations in terms of the objects that can be seen and their relationship. When the software developer provides him these objects as software components, he can work on the level of his own specialism.

At design time, the designer performs two tasks:

1.

Choosing and customising the components, i.e., the visible objects of the scene. This involves selecting their size, shape parameters, colour and other visible attributes, initial position, etc.

2.

Making connections between the objects. These connections can be seen as joints, describing how two objects can move relative to each other.

As an example, consider the construction of a bicycle. This involves the components frame, handlebar, pedals, and two wheels. The parts are connected by so-called pin-joints and, for the connection between pedals and rear wheel, an orientation constraint that forces the wheel and pedals to revolve synchronously. The wheels are connected to the surface with a special wheel connection.