TAPESTRY: The Art of Representation and Abstraction
Pseudo-primitive
DEFINITION
A portion of a drawing which is usually presented to the operator as if it were a single primitive, but which is entered into the database as a collection of lower-order primitives, as when a rectangle is created as four lines.
EXPLANATION
One way to overcome some of the limitations of a vector graphics program without making more complex data (thus making the modification cheaper in terms of programming), is to use the user-interface as a translator between a complex graphic and a simpler database.
OPERATION
The user interface may prompt you for specific data entries, and use the resulting data (plus some algorithmic manipulation) to calculate a series of simpler primitives, which it feeds to the database.
Thus, to create a multi-sided polygon in a program that really only supports lines, the software could be altered to prompt for the center, a point on the radius, and the number of sides. Then, rather than storing this information in a database, the program computes the end-point coordinates for a series of lines which satisfy the input data, and stores these lines into the database. At the end of the operation, the information about center, radial point, and number of sides is discarded.
BENEFITS
Software may be fairly easily enhanced to provide graphic components (polygons, multi-line walls, faceted spheres, etc.) which would be difficult to provide otherwise, and hard for the user to draw.
LIMITATIONS
Most of the limitations arise from the fact that the conceptual structure which the graphic represents is not present in the data. Thus, if you looked at the "polygon" described by the process above, you might wish to change the number of sides, or snap to the center. While these are reasonable operations for a true polygon, you would discover that these operations are not possible on a pseudo-primitive polygon.
Last updated: October, 2017
