kicad-developers team mailing list archive

[Jeff Young <jeff@xxxxxxxxx>]

The non-zero width edges might be creating even larger problems.  If we have a round edge and we generate 32 segments for it, and those segments are non-zero width, then don’t we generate another 32 lines at the end of each segment to make it round?  Or do we use some kind of shader there?

> On 10 May 2019, at 18:30, Mário Luzeiro <mrluzeiro@xxxxx> wrote:
> 
> Hi Tomasz,
> 
> This is an interesting challenge!
> 
> Did you consider other approaches apart from the ones you listed?
> 
> I have no full knowledge how GAL is rendering so maybe some of my suggestions may not make sense.
> 
> I believe GAL is already doing some cache of the layers using textures.
> It may not be possible to get a full buffer resolution of the board ( eg memory limitation? )
> but could be possible to implement some kind of techniques used on game engines?
> For instance: trying to render just the visible part of the board ( culling ) or on the case on render the full board, implement some kind of "level of detail" to render a less accurate version ? ( eg as you pointed the vias could be a special case and simplified while on distance )
> 
> Out of curiosity, is 3D viewer able to render that board? :P
> Would be possible to share that Victor-s project or where we can get it?
> 
> Regards,
> Mario Luzeiro
> 
> ________________________________________
> From: Kicad-developers <kicad-developers-bounces+mrluzeiro=ua.pt@xxxxxxxxxxxxxxxxxxx> on behalf of Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx>
> Sent: 10 May 2019 17:33
> To: Kicad Developers
> Subject: [Kicad-developers] Kicad's way of drawing filled zones
> 
> 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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