Perspective Projection of Non-Convex Polyhedra
Lo, S.H.
International Journal For Numerical Methods in Engineering, John Wiley and Sons, Ltd, Vol 26, pp.1485-1506, 1988
An algorithm is presented for removing hidden lines for isometric and perspective projections of three dimensional objects. An object can be regarded as being made up of a number of planes. Considering planes as the basic element of a picture, non-convex polyhedra can be displayed directly without prior subdivisions into convex ones. Lines connecting nodal points are first retreived from the model to be plotted by a simple but efficient technique. On the picture planes, each unique line is examined in turn to see if it is totally or partially hidden. The intersections between a unique line and a projected plane (with or without openings) are determined by a new method which, eben in the presence of numerical errors, will always give correct intersection information. Unlike many classical algorithms, intersections are determined by a single formula without tedious case subdivisions. With little additional calculations, object penetrations can also be tackled.
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