Strange lines in outline mode of custom pad made from overlapping arcs

[Rene Poeschl]

See screenshot and attached footprint

visible in all 3 toolsets. But not in the 3d viewer.

If i add copper and make the paste pullback <0 i get the result of the second screenshot (teeth like end. -> meaning the lines really represent holes in the pad shape. But there are no straight features in this area of the pad. At least not in that direction.)

---

Application: kicad
Version: 5.1.2-f72e74a~84~ubuntu16.04.1, release build
Libraries:
    wxWidgets 3.0.2
    libcurl/7.47.0 OpenSSL/1.0.2g zlib/1.2.8 libidn/1.32 librtmp/2.3
Platform: Linux 4.15.0-48-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.58.0
    OpenCASCADE Community Edition: 6.8.0
    Curl: 7.47.0
    Compiler: GCC 5.4.0 with C++ ABI 1009

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    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

[Rene Poeschl (poeschlr)]

This might have something to do with floating point errors as it only happens if i calculate the arcs to be touching but not overlapping. If the arcs overlap these lines vanish.

[jean-pierre charras (jp-charras)]

@Rene
Are you sure you attached the right test_ring.kicad_mod:
It contains no arc, just circles, and I cannot reproduce your issue.

[Rene Poeschl (poeschlr)]

You are right i seem to have uploaded the wrong footprint. I do no longer have the exact same footprint. So i generated a new one.

Kicads measure tool seems to round to 3 digits so i am not able to really determine it within kicad. (why would this tool even round without me telling it to do that? It is basically useless that way if i want to really see if a user supplied the footprint correctly. For us librarians it is not enough if it is correct to n digits. It must be correct to all available ones. But that will be a different bug report shortly.)

Meaning i checked it manually.

One start point is at (3.00812, 0.37375) -> radius 3.03124974175669 The other on (2.516143, 0.37375) -> radius 2.54375011723813 both arcs are set to line width 0.4875 the difference between the radii is 0.4874996245185601 which is less than the line width -> they should overlap.

[jean-pierre charras (jp-charras)]

@Rene,

I had a look into your footprint.

I don't think there is a bug in Kicad.

The problem is only due to the fact the footprint area is "painted" by 3 arcs, but when an area is painted by lines or any other shapes, they *must* overlap, not just touching.
This is true for any painted shape (even painted with lines, unless special cases).

Moreover, when using arcs, the arcs are converted to an approximate polygon shape, and therefore having overlapping arcs is mandatory.

[Rene Poeschl (poeschlr)]

What would be the minimum amount of overlap necessary for this to reliably work?

[jean-pierre charras (jp-charras)]

0.1mm as minimum amount of overlap is a reasonable value for me.

[Michael Kavanagh (michaelkavanagh)]

It is certainly a weird artefact... Should this be triaged as a bug or closed as won't fix?

[Wayne Stambaugh (stambaughw)]

I'm tempted to make this invalid as it doesn't appear to be bug but I don't have a strong opinion one way or another. Anyone else want to weigh in on this before I change it?

[Seth Hillbrand (sethh)]

I agree with JP that this isn't really a bug per-se. But it does look funny an we could clean up the display. Offhand, I'm not sure how but maybe mark as wishlist in case the solution becomes obvious with time.

[Wayne Stambaugh (stambaughw)]

I will mark as wishlist. We can always change it if we decide not to fix it.

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2421