kicad-developers team mailing list archive

[Nick Østergaard <oe.nick@xxxxxxxxx>]

2014-10-17 14:22 GMT+02:00 Mark Roszko <mark.roszko@xxxxxxxxx>:
> Alright, I've played around. It appears there is many CAM/gerber
> software that cannot handle G75 arcs that are full 360 degrees. I
> tested this with the board from Jon and the 1 pin test board from
> Nick. If I generate 359 degree arcs, the 3d viewer is happy and draws
> good circles. If I generate 360 degrees then the arcs disappear/screw
> up.

What are the names of the viewers you have seen that could not handle
it correctly?

> As far as I can tell, the math is right for the arcs regardless of 360
> or 359. I think it's because the start point == end point for a 360
> degree arc, that some viewers may break down due to their graphics
> libraries.
>
> I modified KiCAD to generate the circles as two arcs and the same
> viewers seem happy.
>
> i.e. I made
>
> void GERBER_PLOTTER::Circle( const wxPoint& aCenter, int aDiameter,
> FILL_T aFill,
>                              int aWidth )
> {
>     Arc( aCenter, 0, 3600, aDiameter / 2, aFill, aWidth );
> }
>
> into
>
> void GERBER_PLOTTER::Circle( const wxPoint& aCenter, int aDiameter,
> FILL_T aFill,
>                              int aWidth )
> {
>     Arc( aCenter, 0, 1800, aDiameter / 2, aFill, aWidth );
>     Arc( aCenter, 1800, 3600, aDiameter / 2, aFill, aWidth );
> }
>
> Many other CAD software also generate circles as multiple arcs instead
> of a full g75.

Seems like a workaround to me, but could be good info for Mitch, who
can possibly handle that when he gets the gerbers from his custumes,
and modify the full circles to this.

But because the gerber specification says that this kind of arc is
indeed a circle, kicad should continue to generate it.

> Attached are my generated gerbers, 360 won't work, but 270, 359 and
> split arcs will work I believe.