Re: [femm] zoomier

[David Meeker <dmeeker@xxxxxxxx>]

Boyd Evans wrote:

> I am using femm to calculate forces on relatively small features and have
> found that I can't always zoom in as close as I need to. This is 
> important
> when creating geometry, applying properties, and when selecting areas for
> results. I really enjoy the software otherwise.
>
> Thanks,
> Boyd
The reason that there is a limit on the zoom is that the program uses 
the "built-in" line drawing routines in Visual C++. (e.g. MoveTo, 
LineTo, etc.). The arguments to these functions are the end points of 
the lines in the problem's geometry in screen coordinates. Coordinates 
that are off-screen can be entered as arguments. If some part of the 
line passes through the viewable screen, that part is supposed to be 
plottted. These functions take 32-bit integers as the arguments for 
coordinates, but they seem to go berzerk if the coordinates sent to the 
routine are actually bigger than 16 bit values--go figure. To keep the 
display well-behaved, I've made the program limit the zoom so that none 
of the geometry ends up with screen coordinates larger than +-2^15. I 
suppose this was the lazy man's way to "fix" the problem.

I may be missing some obvious fix here--it wouldn't be the first time. 
Otherwise, it seems like one would have to write wrappers for the CDC 
plotting routines so that long lines and overly large objects get 
truncated before an attempt is made at plotting them.

Dave.
--
David Meeker
email: dmeeker@xxxxxxxx
www: http://femm.berlios.de/dmeeker