Clearance arcs in zone fills are not accurate

Bug #1017653 reported by Lorenzo Marcantonio on 2012-06-25
22
This bug affects 4 people
Affects Status Importance Assigned to Milestone
KiCad
High
Unassigned

Bug Description

When filling a zone around a circular feature the circle is subdivided in 16/32 steps, forming a polygon.

However the clearance is applied to the vertices so the polygon sides (which are chords to the clearance circle) are in fact nearer, giving clearance faults. In other words: the polygon is inscribed in the circle, while it should be circumscribed.

I think it could be fixed just multiplying the radius with a fixed constant (depending on the number of sides)

Workaround: just use a little bigger clearance

Martin Errenst (imp-d) wrote :

I can partly reproduce this problem with:
Application: Pcbnew
Version: (2014-02-21 BZR 4711)-product Release build
wxWidgets: Version 2.9.5 (debug,wchar_t,compiler with C++ ABI 1002,GCC 4.6.3,wx containers,compatible with 2.8)
Platform: Linux 3.10.17-gentoo x86_64, 64 bit, Little endian, wxGTK
Boost version: 1.54.0
         USE_WX_GRAPHICS_CONTEXT=OFF
         USE_WX_OVERLAY=OFF
         KICAD_SCRIPTING=OFF
         KICAD_SCRIPTING_MODULES=OFF
         KICAD_SCRIPTING_WXPYTHON=OFF
         USE_FP_LIB_TABLE=HARD_CODED_ON
         BUILD_GITHUB_PLUGIN=ON

There's some priority conflict with the clearance settings for the zone compared to the one from the pad.
The pad got an net-pad clearance of 1mm (see small yellow ring), and the zone a clearance of 0.5mm configured.
Refilling the zone causes the filling to enter inside the yellow clearance ring from the pad.
(Setting both clearances to the same value yields correct results.).
If both settings are not identical, the zones edge next to the pad are not straight and some kind of sprockets are there (below the lines of the not-connected cross) - see attached screenshot.

Changed in kicad:
status: New → Confirmed
importance: Low → High
tags: added: clearance pcbnew zones
Martin Errenst (imp-d) wrote :
tags: added: arcs
Nick Østergaard (nickoe) wrote :

This looks to be fixed, probably in rev 5679, which also closed #1458188. This was tested in 5732.

Changed in kicad:
status: Confirmed → Fix Committed
Jon Neal (reportingsjr) on 2015-09-25
Changed in kicad:
status: Fix Committed → Fix Released
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