The Use of Points as a Display Primitive

Marc Levoy and Turner Whitted

Technical Report 85-022, Computer Science Department,
University of North Carolina at Chapel Hill, January, 1985.


As the visual complexity of computer generated scenes continues to increase, the use of classical modeling primitives as display primitives becomes less appealing. Customization of display algorithms, the conflict between object order and image order rendering and the reduced usefulness of object coherence in the presence of extreme complexity are all contributing factors. This paper proposes to decouple the modeling geometry from the rendering process by introducing the notion of points as a universal meta-primitive. We first demonstrate that a discrete array of points arbitrarily displaced in space using a tabular array of perturbations can be rendered as a continuous three-dimensional surface. This solves the long-standing problem of producing correct silhouette edges for bump mapped textures. We then demonstrate that a wide class of geometrically defined objects, including both flat and curved surfaces, can be converted into points. The conversion can proceed in object order, facilitating the display of procedurally defined objects. The rendering algorithm is simple and requires no coherence in order to be efficient. It will also be shown that the points may be rendered in random order, leading to several interesting and unexpected applications of the technique.

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The paper © Copyright 1985 by Marc Levoy and Turner Whitted