Non-Photorealistic Computer Graphics Library

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Found 3 item(s) authored in "1977".

Proceedings Automated contour mapping using triangular element data structures and an interpolant over each irregular triangular domain
C. M. Gold, T.D. Charters, J. Ramsden.
ACM SIGGRAPH Computer Graphics, Vol. 11, No. 2, pp. 170--175, 1977. [BibTeX]

Proceedings ECOSITE: an application of computer-aided design to the composition of landforms for reclamation
Robert Mallary, Michael Ferraro.
Proc. of SIGGRAPH '77, pp. 1--7, 1977. [BibTeX]

Proceedings Hidden surface removal using polygon area sorting

Author(s): Kevin Weiler, Peter Atherton.
Proceedings: Proc. of SIGGRAPH '77, pp. 214--222, 1977.
[BibTeX] Find this paper on Google

A polygon hidden surface and hidden line removal algorithm is presented. The algorithm recursively subdivides the image into polygon shaped windows until the depth order within the window is found. Accuracy of the input data is preserved. The approach is based on a two-dimensional polygon clipper which is sufficiently general to clip a concave polygon with holes to the borders of a concave polygon with holes. A major advantage of the algorithm is that the polygon form of the output is the same as the polygon form of the input. This allows entering previously calculated images to the system for further processing. Shadow casting may then be performed by first producing a hidden surface removed view from the vantage point of the light source and then resubmitting these tagged polygons for hidden surface removal from the position of the observer. Planar surface detail also becomes easy to represent without increasing the complexity of the hidden surface problem. Translucency is also possible. Calculation times are primarily related to the visible complexity of the final image, but can range from a linear to an exponential relationship with the number of input polygons depending on the particular environment portrayed. To avoid excessive computation time, the implementation uses a screen area subdivision preprocessor to create several windows, each containing a specified number of polygons. The hidden surface algorithm is applied to each of these windows separately. This technique avoids the difficulties of subdividing by screen area down to the screen resolution level while maintaining the advantages of the polygon area sort method.

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