Re: gEDA-user: PCB+GL Progress

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Mon, 2009-02-23 at 20:57 -0500, DJ Delorie wrote:
> I wonder if we could increase the allowed arc gap (i.e. reduce the
> number of triangles used to make a curve) if the program is "busy" and
> later redraw with higher resolution when the system is "idle".

For extra clever-points, if you make sure the reduced complexity
rendering under-fills, you could perhaps even add the extra complexity
without having to repaint the whole scene.

I suspect that somewhere along the lines here, caching, and / or
textures may play an important role in getting the speedups.

(I could pre-render a semi-circular line-cap texture at various
line-sizes for the given zoom level, and stamp it down onto a textured
quad, rather than using 3 or more triangles). You could even get
anti-aliased line-caps pretty easily then... if you wanted.

I got the feeling (not that I'm an avid gamer), that lots of games (and
hence graphics card optimisation) tend to favour simple geometry, low
primitive count, and use lots of texture-mapping to make the detail look
better.

If we're just using oodles of primitives, we're probably not taking
advantage of one of the more powerful hardware accelerated portions of
the graphics card.


W.r.t caching..

Most of a PCB board isn't even changing when your editing it. You're
only typically updating 1 layer at once, sometimes all (if you place a
via / pin which clears polygons on other layers).

The question is what caching is sensible (or has a good benefit /
complexity ratio). Right now, polygons still seem to be the favourite
contender for getting higher performance out of the system.

(I'm biased, since I use a lot of polygon fills, and not a lot of text
on my boards).


-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)



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