The conventional suffix for SPHERE files is .sph.
[ST][E|H|S]SPHERE # Keyword # auto-generated texture co-ordinates, only allowed with STSPHERE objects [SINUSOIDAL|CYLINDRICAL|RECTANGULAR|STEREOGRAPHIC|ONEFACE] # next four fields are required Radius Xcenter Ycenter Zcenter
The key word is [ST][E|H|S]SPHERE.
The optional prefix characters mean:
The sphere carries automatically generated texture co-ordinates. See below.
The sphere lives in Euclidean space.
The sphere lives in Hyperbolic space. See Non-Euclidean Geometry.
The sphere lives in spherical space. See Non-Euclidean Geometry.
Sphere objects are drawn using meshes which are rectangular in a polar
co-ordinate system, with the equatorial plane parallel to the
x,y-plane. Their smoothness, and the time taken to draw them,
depends on the setting of the dicing level, 10x10 by default. From
Geomview, the Appearance panel, the <N>ad keyboard command, or a
dice nu nv Appearance attribute sets this.
Texture co-ordinates are generated for STSPHERE objects; the
keyword following the initial STSPHERE keyword defines the way
this is done. It follows the conventions of the mktxmesh
Perl-script which comes with the Orrery.
sinusoidal equal-area projection
cylindrical proj: s is the longitude, t is the latitude
rectangular proj: s is the longitude, t is sin(latitude)
(i.e. z co-ordinate in the sphere’s co-ordinate system)
stereographic projection from the south (z=-1) pole
stretch orthographic view of +y hemisphere over both, mirroring