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|Title:||USING RECURSION TO DESCRIBE POLYGONAL SURFACES|
|Abstract:||We describe a three dimensional graphics system called PG (Polygon Groper) and its use by artists for defining and viewing solid objects. A simple set of commands in PG are used to manipulate 3D models. The models are stored as a hierarchy of objects, where each object represents a geometrical transformation of another object or a primitive polygon. It has been found that a hierarchical structure provides a more powerful way of building and manipulating 3D objects than conventional linear structures. The object hierarchy also allows recursion to be used to describe pictures which are difficult or impossible to define in other graphics systems without considerable programming effort. Although any recursive process may be expressed iteratively, a certain class of pictures is more concisely defined and more easily visualised recursively. Many tools are available to aid the artist manufacture primitive objects. These tools generate the surface polygons to describe different solids. PG offers a number of alternative viewing algorithms. These provide the artist with successively higher quality images at the cost of correspondingly greater time for computation. PG is an integral part of the Graphicsland System, a film animation system under development at the University of Calgary.|
|Appears in Collections:||Wyvill, Brian|
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