# [pstricks] It might be a bug in finding angle

Luis Sequeira lfsequeira at gmail.com
Sun Jul 29 21:04:01 CEST 2012

When you specify a node point, the origin parameter has no meaning and therefore is ignored:

> \psarcn[origin={O}](O)...

is in fact equivalent to

> \psarcn(O)...

The node point is NOT and alias to a pair of coordinates, it is a point in the plane, independent of the coordinate axes. Therefore (O) will always represent the same point, no matter what the origin is.

LS

> Dear Luis,
>
> I still don't understand why the arc center becomes (6,6) for the second example but it is (3,3) in for the first example.
> In my understanding, if \pnode(3,3){O} then \psarcn[origin={O}](O)... should be identical to the following:
>
> 	* \psarcn[origin={O}](3,3)...
>
> 	* \psarcn[origin={3,3}](O)...
> 	* \psarcn[origin={3,3}](3,3)...?
>
> I have not found the details in PSTricks manual how PSTricks makes assumption and calculates the arc center if nodes and literal numbers are specified.
>
>
> Thank you.
>
>
> Higgs Boson
> ?
>
>
>
> Date: Mon, 23 Jul 2012 11:34:15 +0100
> From: Luis Sequeira <lfsequeira at gmail.com>
>
>
> There is a bug in your code...
>
> In the second version, you have
>
> \psarcn[origin={O},linecolor=red]{->}(3,3) ....
>
> You set the origin at (O), which has coordinates (3,3) so now your center (3,3) is actually at (3,3)+(3,3), as appears in the picture.
>
> You should write just
>
> ?  \psarcn[linecolor=red]{->}(3,3) ....
>
> or (perhaps better, since it retains the fact that your coordinates are relative to (O)):
>
> ?  \psarcn[origin={O},linecolor=red]{->}(0,0) ....
>
>
> Luis Sequeira
>
>
> Date: Sat, 21 Jul 2012 17:52:52 -0700
> From: Counter Terrorist <the.counterterrorist at yahoo.com>
>
> Dear Mr. Herbert,
>
> I found a bug in PSTricks.?
>
> Even though the points (O) and (3,3) represent the same point,
> the second pspicture produces an arc at a wrong pivot.?
>
>
>
> \documentclass[pstricks,border=1cm]{standalone}
> \usepackage{pst-eucl}
>
>
> \begin{document}
>
>
> \begin{pspicture}[showgrid=top](9,8)
> \pstGeonode(3,3){O}(5,5){A}(5,1){B}
> \pscircle[linestyle=dashed](O){2}
> \psarcn[origin={O},linecolor=red]{->}
> (O)%<=============== COMPARE THIS ONE
> {2}{(A)}{(B)}
> \psline(A)(O)(B)
> \end{pspicture}?
>
> \begin{pspicture}[showgrid=top](9,8)
> \pstGeonode(3,3){O}(5,5){A}(5,1){B}
> \pscircle[linestyle=dashed](O){2}
> \psarcn[origin={O},linecolor=red]{->}
> (3,3)%<================ WITH THIS ONE
> {2}{(A)}{(B)}
> \psline(A)(O)(B)
> \end{pspicture}?
>
> \end{document}
>