[pstricks] Possible problem with multido and fp when used with pstricks, especially some of the new pst-3dplot routines.

[Bruce Burlton]

I have encountered a problem when trying to use the \fp package within multido and pst-3dplot, that I cannot figure out.  Specifically the problem arises when I try to use an \fp test (\FPifpos...).

I am trying to produce an accurate pspicture of an elliptic orbit, going around the earth.  In this case, the orbit is "centered" with one of its foci (and not the ellipse center) at the center of the earth. In my first solution (rather brute force and dumb ignorance) I used the fp routines to repeatedly determine points on the orbit path in 1 degree steps.  I the used the new pstRotPoint routine written by Herbert Voss to rotate everything into inertial space (a total of three rotations for each point).  After some initial difficulty (mostly my own typing problems) I produced a satisfactory picture.  However, as some portions of the orbit lie above the equatorial plane and some below, I wished to use two different line styles or colors to distinguish them (a bit of a hidden line thing).

As soon as I include an \FPifpos ...\else ...\fi set of statements I produce a "compiler" error that I cannot find. (see below).  I can step or "scroll" through the errors (and if I cut back the number of points to less than 100) can produce the picture I want.  However, I need 360 points to produce a complete and "smooth" curve.  At this point the compilation fails.

Attached are the following files
1)  the .tex file for the example, with the "offending" fp routines commented out
2) a .pdf file produced "without" the offending fp calls.

Note that because of the very large number of fp calls this file takes a few moments to compile.  You will need the latest version of pst-3dplot in order to compile properly.

Subsequently I have found a much more elegant way in which to solve the original problem (i.e. draw a picture of a proper orbit) but would like to know what is wrong.

Thanks

Bruce Burlton
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