[pstricks] [pst-vue3d, pst-3dplot] Meaning of Dobs and Decran

[Patrick Drechsler]

Sorry for the double posting of my OP.

Patrick Drechsler <patrick at pdrechsler.de> writes:

> please ignore my ignorance of the french language, but what do the
> parameter "Dobs" and "Decran" mean and how do these parameters
> influence things in the package "pst-vue3d"? Expecially how these
> parameters influence scaling of the output is a mystery to me.
>
> A brief look in the documentation as well as the code of pst-vue3d did
> not get me any further. I only find lines such as
>
> --8<---------------cut here---------------start------------->8---
> 6 matches for "Dobs" in buffer: pst-vue3d.tex
>      64:\define at key[psset]{pst-vue3d}{Dobs}{\def\psk at TroisD@Dobs{#1}}
>      68:    Dobs=100,Decran=10,%
>     134:    /Dobs \psk at TroisD@Dobs\space def
>     144:    /XpointVue Dobs Cos1Cos2 mul def
>     145:    /YpointVue Dobs Sin1Cos2 mul def
>     146:    /ZpointVue Dobs Sin2 mul def
> 2 matches for "Decran" in buffer: pst-vue3d.tex
>      65:\define at key[psset]{pst-vue3d}{Decran}{\def\psk at TroisD@Ecran{#1}}
>      68:    Dobs=100,Decran=10,%
> --8<---------------cut here---------------end--------------->8---
>
> I have tried to understand how Herbert included Manuel's
> "\SphereThreeD" into pst-3dplot ("\pstThreeDSphere"). I have adopted
> this feature for cylinders (and it appears to work), but I do not
> understand how it works.

Correction: It does not work as expected. See example.

I forgot to post a minimal example demonstrating the source of my
confusion:

--8<---------------cut here---------------start------------->8---
\listfiles
\documentclass{article}
\usepackage{pst-3dplot,pst-vue3d}

\makeatletter
\def\pstThreeDCylinder{\@ifnextchar[{\pst at ThreeDCylinder}{\pst at ThreeDCylinder[]}}
\def\pst at ThreeDCylinder[#1](#2,#3,#4)#5#6{{%
  \psset{THETA=\psk at ThreeDplot@Beta,PHI=\psk at ThreeDplot@Beta,Dobs=10,Decran=10}%
  \psset{#1}%
  \pstThreeDNode(#2,#3,#4){CylinderCenter}%
  \rput(CylinderCenter){\CylindreThreeD(0,0,0){#5}{#6}}%
}\ignorespaces}
\makeatother

\begin{document}

\begin{pspicture}(-4,-4)(4,4)%\psgrid
  \psset{Alpha=30,Beta=30}
  \pstThreeDBox(-1,-1,0)(0,0,2)(1,0,0)(0,1,0)
  \pstThreeDCylinder[Dobs=5](0,0,2){1}{2}
\end{pspicture}

\end{document}
--8<---------------cut here---------------end--------------->8---

,----
|  *File List*
|      min.tex
|  article.cls    2004/02/16 v1.4f Standard LaTeX document class
|   size10.clo    2004/02/16 v1.4f Standard LaTeX file (size option)
| graphicx.sty    1999/02/16 v1.0f Enhanced LaTeX Graphics (DPC,SPQR)
|   keyval.sty    1999/03/16 v1.13 key=value parser (DPC)
| graphics.sty    2001/07/07 v1.0n Standard LaTeX Graphics (DPC,SPQR)
|     trig.sty    1999/03/16 v1.09 sin cos tan (DPC)
| graphics.cfg    2001/08/31 v1.1 graphics configuration of teTeX/TeXLive
|    dvips.def    1999/02/16 v3.0i Driver-dependant file (DPC,SPQR)
| pst-3dplot.sty    2004/07/15 package wrapper for pst-3dplot.tex (hv)
| pstricks.sty    2005/12/19 v0.31 LaTeX wrapper for `PSTricks' (RN,HV)
| pstricks.tex    2005/12/22 v1.14 `PSTricks' (tvz)
|   xcolor.sty    2007/01/21 v2.11 LaTeX color extensions (UK)
|    color.cfg    2001/08/31 v1.1 color configuration of teTeX/TeXLive
| pst-3dplot.tex    2005/02/19 v1.63 `PST-3dplot' (hv)
| pst-xkey.tex    2005/02/22 v1.5 PSTricks specialization of xkeyval (HA)
|  xkeyval.sty    2005/08/12 v2.5d package option processing (HA)
|  xkeyval.tex    2005/08/12 v2.5d key=value parser (HA)
| pst-vue3d.sty    2000/07/15 package wrapper for pst-vue3d.tex (ML)
| pst-vue3d.tex    2005/02/19 v1.63 `PST-VUE3D' (ML)
`----

Thankful for any pointers

Patrick
-- 
Ist das Hirn zu kurz gekommen, wird sehr gern Moral genommen.
(Wiglaf Droste)