The integrated graphics model in MovieScript is simple at the user level and complex at the implementation level, as illustrated in Figure 17.7.
Figure 17.7: Integrated Graphics Model in MovieScript. Uniform interface in
terms of primitive types is constructed to X, DPS/NeWS, and PEX/GL
components of the Open Systems software and implemented,
correspondingly, in terms of the Xlib, GL/PEXlib and PostScript
communication protocols. Additionally, an interface to the AVS server
is constructed, supporting both the subroutine and coroutine operation
modes. The AVS-style extensibility model in terms of the UNIX dataflow
processes is illustrated both for AVS and MOVIE servers. Within this
model, one can also import other graphics models and applications to
the MOVIE environment. This is illustrated on the example of the
third-party X Window application which is configured as a MovieScript
object or operator.
Our main goal is to bring the heterogeneous collection of present standard subsystems (X, Motif/OpenLook, DPS/NeWS, PHIGS/PEX/GL) to the uniform sector of a high-level language. Interfaces to individual subsystems were discussed above. The overall strategy is to build first a uniform set of low-level primitive types for GUI toolkits and three-dimensional servers, structured as smooth extensions of the DPS/NeWS server-based Postscript graphics model for the two-dimensional vector graphics. This interpreted layer is then used in the next stage to design the high-level object-oriented graphics world in terms of more complex derived types. The resulting graphics support is very powerful and unique in some sense: It utilizes fully the available Open Systems graphics software resources; it conforms to one of the standards (PostScript) at the level of primitives; and finally, it provides the user-friendly, intuitive, and complete programming interface for modern graphics applications.
As an independent component, we provide also the MovieScript interface to dataflow packages such as AVS/Explorer. Both coroutine and subroutine models for MOVIE-based AVS modules are supported, which allows for diverse interaction patterns between MOVIE and AVS servers. The AVS interface is redundant since the graphics functionality of systems such as AVS/Explorer will soon be included in the PEX/GL-based 3D MOVIE model, but it is useful in the current stage where various components of the 3D MOVIE model are still in the implementation process. In particular, the AVS interface was used in the Map Separates application, providing high-quality three-dimensional display tools for the MovieScript field algebra-based imaging and histogramming. We discuss this application in Chapter 3.