VUTRAX SOFTWARE ADVICE NOTICE 117 - 6 July 1993

     PostScript Output - Uncompleted Arcs for Circular Pads

Some  PostScript  interpreters  plot  circular  pads  with  white
centres  with  a  small  notch  at  the 0 degrees position of the
outside of the pad. This is a numeric fault in  the  interpreter,
but can usually be rectified by a small change to the appropriate
PSCRIPT?.PXY file.

Requirements to see the fault:-

  o Round Pads are plotted (as a default or Explicit Shape).

  o Option Q4 (White Space at Hole Centre) is specified.

Characteristics making the fault more likely:-

  o Large Circular pads (or small pads highly magnified).

  o High resolution plotting (e.g. 600 d.p.i. or more).


The offending pads are  drawn  by  drawing  360  degree  arcs  of
appropriate width. For some reason some interpreters do not fully
close the arc.  The  fix  is  to  draw  more  than  360  degrees.
Unfortunately  our  Postscript specification does not specify the
interpretation of arcs over 360 degrees, and  we  prefer  not  to
risk   malfunction   by   doing   this  routinely.  However,  all
interpreters to which we have access do as  we  would  hope  with
such parameters.

To apply the change, use a plain text editor on  the  appropriate
selection of PSCRIPT?.PXY and apply the following change:-

  o A few lines before the end of the file find the definition

    % Vutrax Circle draw assuming stack = <wid> <xc> <yc> <rad>
     /vc { newpath 0 360 arc setlinewidth stroke
         } def

  o Alter 0 360 to 0 361 and test it.

  o If this does not work try changing to -1 360.


The 0 360 sequence  appears  unchanged  near  the  start  of  the
generated  PostScript  output.  If  you  prefer you can write the
output to a file, and apply any trial to the output file that  is
subsequently copied to the printer.