IMAGYS: a language for interactive spatial modelling and graphics
James Benjamin Hayfron Acquah · 1991
This dissertation describes the Imagys language, which attempts to bring to geometric modelling and interactive graphics the flexibility of specification and the power of expression that are characteristic of programming languages. This is in contrast to the traditional graphics subroutine package approach, which suffers from a clumsy syntax and poor readability, a lack of conciseness and flexibility, and the absence of translation-time graphics error checking by the underlying language. The language provides direct support for several important concepts which are essential for developing high-level interactive graphics systems and applications. These concepts include object-level concurrency, an event-driven execution mode for implementing flexible dialogue styles and for modelling persistent non-deterministic behavior. Dynamic update for animation and direct manipulation is supported when the data ports of objects are attached together to form a functional network. The language enforces the separation of modelling, interaction, and presentation code, to promote rapid prototyping and the easy modification of user interfaces. Other features of the language support rapid program development. These include generic classes and modules, a simple multiple inheritance scheme, and polymorphic types. The language makes a clear distinction between objects and values, and supports a valuetype hierarchy similar to the class inheritance hierarchy. The valuetype hierarchy provides the basis for a flexible system of strongly-typed polymorphic functions and classes. The dissertation also describes the IMGS system, a prototype hierarchical spatial modelling and graphics system implemented as a collection of classes in the Imagys language. The IMGS provides facilities for modelling objects of arbitrary complexity in multi-dimensional spaces. Parts of objects are constructed from an extendible set of primitive geometric shapes such as points, curves, surfaces, and solids. The spatial attributes of objects, such as color and other material properties, are also modelled by shapes. The IMGS provides hierarchical structuring facilities for constructing assemblies and sub-assemblies of these parts. The system provides a set of parametric shaping functions which can be applied to the basic set of shapes to create more complex shapes of arbitrary parametric dimension. In this way, the system can be user-extended to support modelling at higher levels of abstraction. The shaping functions can also be used to extend the set of available geometric transformation primitives used for viewing and animation.