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

[Herbert Voss]

Bruce Burlton wrote:
> 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...).

use this order of loading the packages

\usepackage{multido}$  version >=1.41
\usepackage[nomessages]{fp}
%\usepackage{pstfp}%  not needed
\usepackage{pstricks,pst-3dplot}

and for the if part

\dimen0=\zVal pt
\FPifgt{\number\dimen0}{0} \let\pstyle\above \else \let\pstyle\below \fi

Then everything should be ok, at least for me ...

Herbert


\documentclass[12pt]{article}
%
%  Packages
%
\usepackage{amsmath,amssymb}
\usepackage[english]{babel}
\usepackage[latin1]{inputenc}
\usepackage{multido}
\usepackage[nomessages]{fp}
%\usepackage{pstfp}
\usepackage{pstricks,pst-3dplot}


\newpsstyle{above}{linewidth=1.2pt}
\newpsstyle{below}{linewidth=0.3pt}
\def\pstyle{}
%
\def\td{57.29578}%

\def\major{4}\def\minor{3}%  semi major and minor axes
\FPeval\ECC{(major*major-minor*minor)^(.5)/major}%  eccentricity
%\FPset\ECC{0.6614}%
\FPeval\Num{major*(1-ECC*ECC)}% numerator of radius function
%\FPset\Num{2.2502}%
\FPeval\Ra{major*(1+ECC)}% apogee radius
%\FPset\Ra{4.6614}%
\FPeval\Rp{major*(1-ECC)}% perigee radius
%\FPset\Rp{1.3544}%
\def\Inc{-30}\def\Node{225}\def\perg{30}% inclination, Node and arg. of 
perigee definitions
\def\xVal{}\def\yVal{}\def\zVal{0}\def\xValold{0}\def\yValold{0}\def\zValold{0}%
\def\xTemp{}\def\yTemp{}\def\zTemp{}\def\tempa{}\def\tempb{}\def\tempc{}\def\temp{}%
\def\Temp{}%

\begin{document}
%
   \begin{pspicture}(-5,-4)(5,4)%
     \psset{Alpha=155}%
     \pstThreeDCoor[xMin=0,yMin=0,zMin=0]%  inertial frame
     \pstUThreeDPut[270](4,0,0){$\Upsilon$}%
     \pstThreeDSphere[linecolor=blue,linewidth=.3pt](0,0,0){1}%  draw 
"earth"
     \pstThreeDCircle(0,0,0)(1,0,0)(0,1,0)%  draw equator
     \pstThreeDCircle[linestyle=dotted](0,0,0)(\Rp,0,0)(0,\Rp,0)%  draw 
equatorial plane
     \pstThreeDCircle[linestyle=dotted](0,0,0)(4,0,0)(0,4,0)%  draw 
equatorial plane
     \pstThreeDCircle[linestyle=dotted](0,0,0)(\Ra,0,0)(0,\Ra,0)%  draw 
equatorial plane
     \pstThreeDCircle[linestyle=dotted](0,0,0)(5.3,0,0)(0,5.3,0)%  draw 
equatorial plane
     \pstThreeDCircle[linestyle=dotted](0,0,0)(2.5,0,0)(0,2.5,0)%  draw 
equatorial plane
     \pstRotPointIIID[RotX=\Inc](0,0,6){\xVal}{\yVal}{\zVal}% orbit 
normal vector, about x (inc)
     \pstRotPointIIID[RotZ=\Node](\xVal,\yVal,\zVal){\hx}{\hy}{\hz}% 
about z (node)
 
\pstThreeDLine[SphericalCoor=true,linestyle=dashed,arrows=->](0,0,0)(7,45,0)% 
line of nodes
     \pstThreeDLine[linecolor=brown,arrows=->](0,0,0)(\hx,\hy,\hz)% 
draw orbit normal vector
%  initialize orbit plot
     \FPeval\xVal{Num/(1+ECC)}% initialize x
     \FPadd\temp{1}\ECC%
     \FPdiv\xVal\Num\temp%
     \FPset\yVal{0.}%
 
\pstRotPointIIID[RotZ=\perg](\xVal,\yVal,0){\tempa}{\tempb}{\tempc}% 
about z (omega)
 
\pstRotPointIIID[RotX=\Inc](\tempa,\tempb,\tempc){\xTemp}{\yTemp}{\zTemp}% 
  about x (inc)
 
\pstRotPointIIID[RotZ=\Node](\xTemp,\yTemp,\zTemp){\xValold}{\yValold}{\zValold}% 
  about z (node)
 
\pstThreeDLine[linecolor=green,arrows=->](0,0,0)(\xValold,\yValold,\zValold)% 
perigee vector
     \pstThreeDNode(\xValold,\yValold,\zValold){Perigee}
     \uput[180](Perigee){Perigee}%  label perigee
%  main loop, eval orbit coords (x,y) in orbit plane, then rotate 
(x,y,0) to inertial
%    \FPdebugtrue
     \Multido{\ia=0+1}{360}{%
       \FPdiv\temp\ia\td
       \FPsincos\tempb\tempc\temp
% r, in the orbit plane
       \FPmul\temp\ECC\tempc
       \FPadd\temp\temp{1}
       \FPdiv\tempa\Num\temp
       \FPmul\xVal\tempa\tempc% x, in the orbit plane
       \FPmul\yVal\tempa\tempb% y, in the orbit plane
% rotate it to the inertial frame
 
\pstRotPointIIID[RotZ=\perg](\xVal,\yVal,0){\tempa}{\tempb}{\tempc}% 
about z (omega)
 
\pstRotPointIIID[RotX=\Inc](\tempa,\tempb,\tempc){\xTemp}{\yTemp}{\zTemp}% 
  about x (inc)
 
\pstRotPointIIID[RotZ=\Node](\xTemp,\yTemp,\zTemp){\xVal}{\yVal}{\zVal}% 
  about z (node)
       \dimen0=\zVal pt
       \FPifgt{\number\dimen0}{0} \let\pstyle\above \else 
\let\pstyle\below \fi
       \pstThreeDLine(\xValold,\yValold,\zValold)(\xVal,\yVal,\zVal)%
       \let\xValold\xVal\let\yValold\yVal\let\zValold\zVal%
     }% end of multido
     \pstThreeDNode[SphericalCoor=true](\Ra,45,0){LN}%
     \uput[270](LN){Line of nodes}%
     \uput{20pt}[50](LN){$i$}%

 
\pstThreeDLine[arrows=->,linecolor=green](0,0,0)(-2.868,-0.189,0.86)% 
draw radius
 
\pstThreeDPut(-2.868,-0.189,0.86){\pstThreeDLine[arrows=->,linecolor=green]%
        (0,0,0)(0.5,-0.866,0)}%  draw velocity
 
\pstThreeDCircle[arrows=->,linecolor=brown,beginAngle=180,endAngle=135]%
        (0,0,0)(3.25,0,0)(0,3.25,0)%  draw node arc
     \pstThreeDPut[SphericalCoor=true](3.25,20,0){$\Omega$}%
     \pstThreeDPut[SphericalCoor=true](2.2,160,0){$\omega$}%   label arg 
of perigee
     \pstThreeDPut[SphericalCoor=true](1.95,190,0){$\theta$}%  label anomaly
     \pstThreeDCircle[arrows=<-,linecolor=brown,beginAngle=0,endAngle=90]%
        (0,0,0)(.9932,-1.4185,-.9999)(1.6378,1.1472,0)%  draw arg of 
perigee arc
     \pstThreeDCircle[arrows=->,linecolor=brown,beginAngle=0,endAngle=-55]%
        (0,0,0)(.9932,-1.4185,-.9999)(1.6378,1.1472,0)%  draw anomaly arc
     \pstThreeDCircle[arrows=->,linecolor=brown,beginAngle=0,endAngle=30]%
        (2.457,1.721,0)(.3442,-.4915,0)(0,0,.6)%  draw inclination arc
     \pstThreeDNode(-2.868,-0.189,0.86){r}%
     \uput{12pt}[135](r){$\vec{v}$}%  label velocity
     \uput[0](0.75,1.25){$\vec{r}$}%  label r
   \end{pspicture}%
%
\end{document}


-- 
http://TeXnik.de/
http://PSTricks.de/
ftp://ftp.dante.de/tex-archive/info/math/voss/Voss-Mathmode.pdf
http://www.dante.de/faq/de-tex-faq/
http://www.tex.ac.uk/cgi-bin/texfaq2html?introduction=yes