Le 10/05/2019 à 18:33, Tomasz Wlostowski a écrit : > 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
Hi Tom, I have a *strong preference* for the solution 3: - It does not require a bumping to GL 3.0. I am not thrilled by this idea. - It works also in Cairo engine. - It fixes a issue in connection calculations: a connection (pad, via track end) is found if the reference position is inside the zone. Inside the zone is currently inside the main polygon, not really the full area (polygon+thick outline), so a few connections are missed. Why I have used polygons with thick outlines: Because the polygon library used at this time did not a good job to inflate polygons (read a really bad job). But this is not the case now with Clipper, that is a really great polygon library. I made a very fast test, and just tried these 2 changes: - do not draw thick outlines - Use 16 segments by circle to create holes and polygon inflate: this is enough for this purpose. I am not sure other ECADs are better. - and inflate the filled polygons by zone min thickness/2 the result is very good: - filled polygon shapes are very good. - the number of segments to draw filled polygons does not significantly change. Of course, using segments to draw thick outlines give a better look for acute angles, but do not mix cosmetic criteria and technical criteria. -- Jean-Pierre CHARRAS _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
