platonicfolding - Man Page

platonicfolding [--display host:display.screen] [--install] [--visual visual] [--window] [--root] [--window-id number] [--delay usecs] [--fps] [--rotate] [--colors color-scheme] [--face-colors] [--earth-colors] [--foldings num-foldings]

The platonicfolding program shows the unfolding and folding of the Platonic solids.  For the five Platonic solids (the tetrahedron, cube, octahedron, dodecahedron, and icosahedron), all unfoldings of its faces are non-overlapping: they form a net. The tetrahedron has 16 unfoldings, of which two are essentially different (non-isomorphic), the cube and octahedron each have 384 unfoldings, of which eleven are non-isomorphic, and the dodecahedron and icosahedron each have 5,184,000 unfoldings, of which 43,380 are non-isomorphic. This program displays randomly selected unfoldings for the five Platonic solids. Note that while it is guaranteed that the nets of the Platonic solids are non-overlapping, their faces occasionally intersect during the unfolding and folding.

The program displays the Platonic solids either using different colors for each face (face colors) or with a illuminated view of the earth (earth colors).  When using face colors, the colors of the faces are randomly chosen each time a new Platonic solid is selected.  When using earth colors, the Platonic solid is displayed as if the sphere of the earth were illuminated with the current position of the sun at the time the program is run.  The hemisphere the sun is currently illuminating is displayed with a satellite image of the earth by day and the other hemisphere is displayed with a satellite image of the earth by night.  The specular highlight on the illuminated hemisphere (which is only shown over bodies of water) is the subsolar point (the point on earth above which the sun is perpendicular).  The earth's sphere is then projected onto the Platonic solid via a gnomonic projection.  The program randomly selects whether the north pole or the south pole is facing upwards.  The inside of the earth is displayed with a magma-like texture.

At the beginning of each cycle, the program selects one of the five Platonic solids randomly and moves it to the center of the screen.  It then repeatedly selects a random net of the polyhedron and unfolds and folds the polyhedron.  The unfolding and folding can occur around each edge of the net successively or around all edges simultaneously.  At the end of each cycle, the Platonic solid is moved offscreen and the next cycle begins.

While the Platonic solid is moved on the screen or is unfolded or folded, it is rotated by default.  If earth colors are used, the rotation is always performed in the direction the earth is rotating (counterclockwise as viewed from the north pole towards the center of the earth).  This rotation optionally can be switched off.

platonicfolding accepts the following options:

--window

Draw on a newly-created window.  This is the default.

--root

Draw on the root window.

--window-id number

Draw on the specified window.

--install

Install a private colormap for the window.

--visual visual

Specify which visual to use.  Legal values are the name of a visual class, or the id number (decimal or hex) of a specific visual.

--delay microseconds

How much of a delay should be introduced between steps of the animation.  Default 25000, or 1/40th second.

The following options determine whether the Platonic solid is being rotated.

--rotate

Rotate the Platonic solid (default).

--no-rotate

Do not rotate the Platonic solid.

The following three options are mutually exclusive.  They determine how to color the Platonic solid.

--colors random

Display the Platonic solid with a random color scheme (default).

--colors face (Shortcut: --face-colors)

Display the Platonic solid with different colors for each face.  The colors of the faces are identical on the inside and outside of the Platonic solid.

--colors earth (Shortcut: --earth-colors)

Display the Platonic solid with a texture of earth as illuminated by the sun at the time the program is run.

The following option determines how many unfoldings and foldings to perform per cycle.

--foldings random

Use a random number of unfoldings and foldings per cycle (default).

--foldings int

If an integer number is specified, it is clipped to the range 1...20 and the clipped number is used as the number of unfoldings and foldings per cycle.

If you run this program in standalone mode, you can rotate the Platonic solid by dragging the mouse while pressing the left mouse button.

DISPLAY

to get the default host and display number.

XENVIRONMENT

to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

XSCREENSAVER_WINDOW

The window ID to use with --root.

X(1), xscreensaver(1),

Takashi Horiyama, Wataru Shoji: Edge Unfoldings of Platonic Solids Never Overlap.  In: 23rd Canadian Conference on Computational Geometry, 2011.

Takashi Horiyama, Wataru Shoji: The Number of Different Unfoldings of Polyhedra.  In: 24th International Symposium on Algorithms and Computation, pp. 623-633, 2013.

Taiping Zhang, Paul W. Stackhouse Jr., Bradley Macpherson, J. Colleen Mikovitz: A solar azimuth formula that renders circumstantial treatment unnecessary without compromising mathematical rigor: Mathematical setup, application and extension of a formula based on the subsolar point and atan2 function.  Renewable Energy 172:1333-1340, 2021.

Copyright © 2025 by Carsten Steger.  Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. No representations are made about the suitability of this software for any purpose.  It is provided "as is" without express or implied warranty.

Carsten Steger <carsten@mirsanmir.org>, 18-mar-2025.