Created attachment 108948 [details] artifacts The preset Bristle_Squared displays the behaviour easily. Actually, it seems to also produce some artifacts inside the main canvas, but it's much worse when outside and on negative coordinates.
Sounds like there are rounding errors when converting the coordinates.
Just fyi, neither https://phabricator.kde.org/D8894 nor https://phabricator.kde.org/D8898 seem to change anything regarding the bristle engine,
(I can confirm on Ubuntu 14.04 - Krita 4.0.0-beta1.1.appimage)
Git commit d3175ce38f93b651addb935ad7ee6ccb19c8720b by Ivan Yossi. Committed on 22/05/2019 at 05:20. Pushed by ivany into branch 'master'. Fix Bristle artifacts on Wrap Around mode Only avoids artifacts being more prominent on wraparound mode M +4 -4 plugins/paintops/hairy/hairy_brush.cpp https://invent.kde.org/kde/krita/commit/d3175ce38f93b651addb935ad7ee6ccb19c8720b
Git commit d678560c7d79a169cf8b3e1c9b28a6afd9fa708b by Boudewijn Rempt, on behalf of Ivan Yossi. Committed on 23/05/2019 at 11:57. Pushed by rempt into branch 'krita/4.2'. Fix Bristle artifacts on Wrap Around mode Only avoids artifacts being more prominent on wraparound mode M +4 -4 plugins/paintops/hairy/hairy_brush.cpp https://invent.kde.org/kde/krita/commit/d678560c7d79a169cf8b3e1c9b28a6afd9fa708b
Setting as fixed as negative coordinate artifacts is no longer an issue