Re: gEDA-user: Gerbv superposition of layers

["Ben Barker" <benjamin.barker@xxxxxxxxx>]

Thanks - that seems to have worked. The gerbv I was using was from a
repository and was quite old. The reason I set all the corresponding
layers to the same colours was that if I XORed two corresponding
layers that were both the same colour, only the differences remained,
everything else would be black. But if I XORed two layers that were
different colours everything remained, but with varying colour
depending upon whether there was overlap or not.
(presumably because the XOR process XOR's every bit of the colour for
each pixel in the two layers, and produces a resultant colour from
this comparison - so only if both colours are the same will black
result)



Cheers,

Ben

On 05/02/2008, Larry Doolittle <ldoolitt@xxxxxxxxxxxxxxx> wrote:
> Ben -
>
> On Tue, Feb 05, 2008 at 08:27:21PM +0000, Ben Barker wrote:
> > I had two gerber files that were almost identical, with a few small
> > differences, and I wanted to compare them.
>
> Cute idea.  Works great.
>
> > I loaded them both into the
> > viewer, and set each layer to the same colour. However, i think my
> > assumptions about the superposition options must be wrong.
>
> I think the results are easier to understand if you use a different
> color, but either way is OK.
>
> > I would have assumed that if I selected superposition via AND the
> > display would show only those areas where there was graphic on both
> > layers - instead the display was entirely black
>
> I can tell you are using a pre-2.0.0 gerbv.  I also observed
> rendering problems with it.  It was sensitive to both the graphics
> card and the order of redraw.  Once you have an area selected,
> try turning all layers off, then on again.
>
> Better still, try gerbv-2.0.0.
>
>     - Larry
>
>
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