Re: gEDA-user: Error in Centroid Calculation

[David Kuehling <dvdkhlng@xxxxxx>]

>>>>> "John" == John Luciani <jluciani@xxxxxxxxx> writes:

> The 2005xxxx version gives the correct centroid or may just default to
> the value of the mark which happens to be the correct centroid for
> this footprint.

Centroid coordinates are computed by averaging the coordinates of all
pads of an element (see hid/bom/bom.c:370). This may coincide with the
mark of the element, if the mark is in the geometric center.

Parts with uneven number of pads and non-symmetric pad positions will
give you headaches, though.

I remember reading in some DIN-EN/IEC standard that XY-data should use
the geometric center of the package /body/ as reference point for an
element.  So for many regularly shaped parts, PCB output should be close
to what your manufacturer expects.

Personally, I would prefer using the element's mark for XY-Data.  This
would give me some control that the current output lacks.  Eg. there are
many packages for which centroid of pads won't work well.  Such as many
SMT transistor footprints.

David
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