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hopfviewer
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Four-dimensional visualization of the Clifford torus.

"Align 4D"
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When this option is selected, the action of the right mouse button is
changed.  It now leaves the torus invariant, and the frame of
reference for the new action is the torus itself.  The (dx, dy)
velocity of the mouse corresponds to a rotation of angle dx in one
plane and a simultaneous rotation of angle dy in the complement plane
(up to some scaling factor).  A torus with a winding of (a, b) is left
fiber-wise invariant by a mouse drag of slope b/a.

Fibers
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A circle consisting of a single color is a Hopf fiber, which may be
clearly seen with a winding of (1, 1) (use "squares" mode or manual
mode).  Adjusting the first "subdomain" field shows how Hopf fibers
trace out a torus.  This parameter along with the "ratio angle"
parameter enables one to see the foliation of S^3 by Hopf fibers.

The surface domain is a single rectangle which is stretched then
rotated (in domain space) to match the winding slope.  Therefore,
ironically, hopfviewer cannot show individual Hopf fibers except
indirectly as explained above.  However, a winding of (n, n + 1) for
higher values of n, say (25, 26), is effectively indistinguishable
from Hopf fibers (that is, you probably won't notice the difference
between a slope of 1.04 and a slope of 1).