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Manuscript Title: A program for perspective views of open surfaces.
Authors: E.A. Olszewski
Program title: TDPLOT3
Catalogue identifier: ACFB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 30(1983)259
Programming language: Fortran.
Computer: IBM 3081.
Operating system: OS/370, MVS.
RAM: 381K words
Word size: 32
Peripherals: graph plotter.
Keywords: General purpose, Perspective projection, Computer display, Stereoscopy, Cylindrical coordinates, Spherical polar Coordinates, Plotting, Hidden-line removal.
Classification: 14.

Nature of problem:
TDPLOT3 constructs either monoptic or stereoptic perspective projections of open surfaces described in spherical polar or cylindrical coordinates and, optionally, displays the top side of the surface in one colour and the underside in another colour.

Solution method:
TDPLOT3 scales the surface so that its projection fits within the specified plot dimensions. It then constructs the perspective projection of the surface, determines which points in the projection are hidden, and, finally, plots the projection with hidden lines removed.

TDPLOT3 generates perspectives of surfaces s(r,theta) parametrized in spherical polar or cylindrical coordinates where the radial, r, and the angular, theta, variables are tabulated in uniform steps. The function s(r,theta) must be single valued, and no part of the display plane on which the surface is projected, when extended to infinity, should intersect the surface.

Unusual features:
TDPLOT3 offers three different types of hidden-line elimination, two of which have been described previously. In the third type, lines visable on the top side of the surfaces are distinguished from those visible on the underside so that a display may be constructed with the perspective of the underside in another color. TDPLOT3 also features a cubic- interpolation routine which generates additional perspective points so that a smoother display of the surface may be constructed without needing additional input data or hidden-line search time. Monoptic and various types of stereoptic views can be produced. The program structure is modular; consequently, those subroutines which are necessary for multi-color plotting may be removed when only single color plotting capabilities are available. Standard ASA FORTRAN 77, compatible with ASA FORTRAN 66, is used except for subroutines which drive the plotter.

Running time:
The time estimates presented here are in equivalent IBM 3081 CPU time (about 0.8 mu s per arithmetic operation). For a typical surface comprising 49 radial by 40 angular points the CPU time required for constructing three different perspectives (two monoptic and one stereoptic) ia approximately 3.1 s, with additional time required for output.