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sphere_tri.m

The function uses recursive subdivision. The first
approximation is an platonic solid, either an icosahedron,
octahedron or a tetrahedron. Each level of refinement
subdivides each triangle face by a factor of 4 (see also
mesh_refine). At each refinement, the vertices are
projected to the sphere surface (see sphere_project).
A recursion level of 3 or 4 is a good sphere surface, if
gouraud shading is used for rendering.
Usage: FV = sphere_tri(shape,Nrecurse,r)
shape is a string, either of the following:
'ico' starts with icosahedron (most even, default)
'oct' starts with octahedron
'tetra' starts with tetrahedron (least even)
Nrecurse is int >= 1, setting the recursions (default 1)
r is the radius of the sphere (default 1)
FV has fields FV.vertices and FV.faces. The vertices
should be triangulated in clockwise order, as viewed
from the outside in a RHS coordinate system.
The returned struct can be used in the patch command, eg:
% create and plot, vertices: [2562x3] and faces: [5120x3]
FV = sphere_tri('ico',4,1);"
lighting phong; shading interp; figure;"
patch('vertices',FV.vertices,'faces',FV.faces,...
'facecolor',[1 0 0],'edgecolor',[.2 .2 .6]);"
axis off; camlight infinite; camproj('perspective');"
See also: mesh_refine, sphere_project