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Re: Kicad's way of drawing filled zones


Does anyone have a good sense of which hardware / software platforms would be impacted by a switch to OpenGL 3.0 as baseline requirement?

As far as I am aware, all commercial tools in the space have more advanced / modern system requirements than KiCad, with the possible exception of Eagle. We have to consider whether supporting old graphics cards goes counter to the desire to have KiCad handle more professional use cases (including large designs).

The integrated Intel GPUs that are old enough to not have OpenGL 3.0 are no longer supported by Intel (everything since HD2000 series has it, as far as I know)


On Fri, May 10, 2019, at 12:33 PM, Tomasz Wlostowski wrote:
> Hi,
> I've been recently playing with Victor's huge 32-layer PCB design and
> trying to improve the performance of pcbnew for larger designs. This
> board causes even pretty decent PCs to crash/render glitches due to
> pcbnew's enormous VBO (Vertex Buffer) memory consumption.
> It turns out it's caused by the way KiCad renders filled zones:
> - the inside of a zone is drawn/plotted as a filled polygon with 0-width
> boundary. This one not a problem - we already triangulate the polygons
> and I recently developed a patch for the OpenGL GAL that allows reusing
> vertices of triangulated polys in the VBO/Index buffer to further reduce
> memory footprint.
> - the thick outline is drawn with rounded segments with the width =
> minimum width of the polygon. Since we don't have arcs in polygons, each
> of round features (e.g. vias) surrounded by a zone gets a ton of tiny
> segments in the polygon outline. Each rounded segment in OpenGL is
> composed of 2 triangles, hence 6 vertices (that can't be reused...). For
> Victor's board it means 1 GB (sic!) of the VBO goes for outlines of the
> polygons alone. Disabling the outline drawing makes the renderer work
> smooth again.
> I've been experimenting with some ways to fix this:
> - generating the thick outline strokes using a Geometry Shader (which
> means bumping up GL 3.0+), which means farewell to many Linux/older
> integrated Graphics users.
> - caching a triangulated polygon which is a boolean sum of the filled
> inside and the thick stroked outline. This takes a lot of time (~2
> minutes for Victor's design) to load and still takes quite a bit of VBO
> memory. Another downside is that the polygons are not fully WYSIWYG
> (outline segments have true rounded corners, while the corners of the
> displayed shape would be approximated with line segments).
> - change the way KiCad handles filled zones to calculate the (stroke +
> inside) boolean sum during zone filling process. It means changes to the
> plotting/GAL/3D code, but no changes to the file format. We'll also be
> forced to inform the users that they have to refill the zones if they
> read a file generated by an older KiCad version.
> Which solution would you prefer?
> Cheers,
> Tom
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