Tracks in positions which offend DRC, pns router and possibly arc approximation

[eelik]

I have a tight design with 0402 components and 0.05mm grid. Arc approximation max err val is 0.001mm. PNS router puts tracks into positions where they violate DRC. They seem to overlap a bit with the sharp corners of the clearance outlines which are quite coarse even with the smallest allowed arc appr max err val. I'm not sure if this can happen when routing from scratch but I get them when moving the existing tracks with PNS.

Application: Pcbnew
Version: (5.1.0-1008-g945eaceb9), release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.61.1 OpenSSL/1.1.1 (WinSSL) zlib/1.2.11 brotli/1.0.6 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) nghttp2/1.34.0
Platform: Windows 8 (build 9200), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8)
    Boost: 1.68.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.61.1
    Compiler: GCC 8.2.0 with C++ ABI 1013

Build settings:
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=OFF
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[Seth Hillbrand (sethh)]

Can you attach an example or video that shows this?

[eelik (eelik)]

This short video shows one of those situations. I've got several of them in the same board, it behaves consistently. This is the first "Track too close to pad" error in the drc window in ~15sec in the video. I'll see if I can reduce the board file and send it here.

[eelik (eelik)]

OK, it should be available in this project. In this saved state the error should be shown by DRC check, it's the only "track too close to pad" error there. It can be edited like in the video.

[Seth Hillbrand (sethh)]

I can verify that this happens.

DRC works on a radius from the corner model, so it will always be more accurate than the PNS router, regardless of the settings we choose until we teach PNS to handle arcs directly (that's an enormous task)

That said, it does seem that there may be an addressable issue here.

The clearance outline coarseness is a different bug and shouldn't really be related here but we should address.

[eelik (eelik)]

I just want to comment on the importance. I got a bunch of these problems in the same board. In some places when I dragged the trace to one direction it overlapped one pad clearance area, and when I tried the other possible direction it overlapped another pad's clearance area. So I had to tweak it manually very carefully (because I have a very tight design). That kind of partly defeats the purpose of PNS. I would consider this as medium.

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/1804