6.0 loses connections when thermal spokes don't intersect the centers of pads

[Seth Hillbrand]

Playing with the new polygon zone fill strategy, I notice that it is more conservative in generating thermal connections than the legacy strategy. This leads to unexpected disconnects.

In the attached board file, the legacy strategy correctly fills the GND zone, connecting to the four pads in the net. Switching to the polygon fill strategy and refilling results in disconnected pads and no fill.

Application: Pcbnew
Version: (5.1.0-1557-g1bfefc61e), debug build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.64.0 OpenSSL/1.1.1c zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) libssh2/1.8.0 nghttp2/1.36.0 librtmp/2.3
Platform: Linux 4.19.0-5-amd64 x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
    Boost: 1.67.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.64.0
    Compiler: GCC 8.3.0 with C++ ABI 1013

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

[Jeff Young (jeyjey)]

@Seth, I think this is a connection problem, not a zone fill problem. Draw a track from one of the ground pins to the zone and the zone will fill.

Note that it does trim the circled spokes in the attached image. But I assume that's not what's the issue here?

[Seth Hillbrand (sethh)]

Might be a connection issue working with the new outline zone fills. Even with the track, the zone fill doesn't make connection to the pads (see image).

[Jeff Young (jeyjey)]

That explains the connection issue.

Note, however, that it's sort of what you asked for. You have the clearance around the middle two pads set to larger than the distance to the center of the GND pads.

[Seth Hillbrand (sethh)]

Agreed. The issue I'm highlighting that we will want to fix before we make the new fill type default is that the connectivity is different between the two fill types. The zone fill does connect properly when using the stroked fill.

[Jeff Young (jeyjey)]

Much to my surprise it appears to be changes to the connection algorithm rather than the fill algorithm that produce this difference. See attached image which shows the fill from 5.1: the thermal spokes are trimmed in a similar fashion and don't intersect with the centers of the pads.

[Seth Hillbrand (sethh)]

@Jeff- 6.0 works fine using the stroked zone fills. It is the polygon-only (no stroke) that doesn't connect.

[Jeff Young (jeyjey)]

I suspect it has something to do with how the connection algorithm is processing the zone edge.

[KiCad Janitor (kicad-janitor)]

Fixed in revision 809a4e3c0e2cf528a3bf4e781f23726bf9129030
https://git.launchpad.net/kicad/patch/?id=809a4e3c0e2cf528a3bf4e781f23726bf9129030

[Wayne Stambaugh (stambaughw)]

"// Wicked witch" LOL. I hope there are not wicked witches in my board design.

[Seth Hillbrand (sethh)]

Nice. I pushed a small fixup for complex board speed.

Also, this exposed a bug in how we were handling connectivity with the old stroked zones that should be fixed now. Thanks for handling this Jeff!

[Jeff Young (jeyjey)]

He he... so before my change it was actually 5.1 that was in error when it was connecting the zones (due to all the width being placed outside).