Incorrect Polygon Offsetting

[EdiCojali]

Having the next polygon and offsetting it by a negative values(not all values) having JoinType::Round i get incorrect polygon with 3 points

54.9410204634, 259.295390514 55.8972892252, 259.208143482 56.4210542645, 259.117807222 56.9763577093, 259.007130787 57.5557437464, 258.876323734 58.1869357683, 258.701590146 58.9093153777, 258.457152819 59.6294785488, 258.177361044 60.3316256861, 257.867231347 60.4642330205, 257.777212663 61.6289743134, 257.189434666 62.1400860738, 256.881755134 63.098552689, 256.165495579 63.6772761732, 255.666904033 64.0249310365, 255.383674574 64.4739750566, 254.968656101 64.8493839336, 254.592806772 65.1676971128, 254.25875636 65.4662334486, 253.900974647 65.7658990156, 253.524450409 66.3596528736, 252.732040123 66.6427795764, 252.328807719 66.8808827129, 251.974957259 67.4962539197, 251.01789538 67.5953995183, 250.863060496 68.210367562, 249.915677898 68.2680738685, 249.824520575 245.355849227, -24.6312149908 245.42917495, -24.742417831 246.777907472, -26.9723388184 247.520178682, -28.5683447264 247.767448829, -29.2266769246 248.192786225, -30.6788284552 248.354342999, -31.453986002 248.54913842, -33.0576006293 248.577379891, -33.8701807042 248.493450485, -35.4844188449 248.383167367, -36.2762722884 248.034223913, -37.8120725671 247.79930514, -38.5514050785 247.526604753, -39.2695459332 246.874547146, -40.6378933118 246.498211033, -41.2864443182 246.090208883, -41.910182866 245.204411246, -43.0678773071 244.765396028, -43.5745186313 243.981761651, -44.395429069 243.668894395, -44.7004875239 243.408725433, -44.9480521693 243.013548306, -45.3165592467 242.859869278, -45.4585853172 242.035919539, -46.2408436879 241.969692479, -46.3019704296 241.852719973, -46.411773387 241.387629467, -46.8349908813 241.184485391, -47.0228427549 17.5400165327, -256.718261428 16.7878800857, -257.213923679 14.6034398162, -258.366058246 12.0298477167, -259.153463796 9.7709422303, -259.385568937 7.87835541135, -259.274780295 7.03897756662, -259.136736441 6.21050512114, -258.938866148 4.75343539035, -258.472948292 4.11697117053, -258.222602844 3.55848606063, -257.979794392 2.74023138505, -257.590294488 2.44470225561, -257.443492726 1.02711009926, -256.793035285 0.9469515535, -256.75425538 0.440886366305, -256.509097782 0.320469720157, -256.451369944 -248.57703079, -139.640687933 -140.639149849, 259.386750373

Red values and distance:

Black values and distance:

[AngusJohnson]

You can get tiny offsetting artefacts when you have relatively tiny segments in your input paths. The offsetting procedure always uses integer coordinates, so when segments are only one or perhaps two unit long (ie after scaling of floating point coordinates), then the necessary rounding can create oddly angled segments that will be exagerated by offsetting. And these tiny segments can occasionaly cause the sorts of artefacts you've noticed. The best way to remove these tiny segments is to call the SimplifyPaths function before (and ideally after) offsetting. And calling SimplifyPaths will also significantly improve offsetting performance.

The image below is a zoomed in snapshot of a small part of your path above (scaled to 6 decimal places). The red vertex has either been affected by rounding or simply misplaced in the code that generated your path (eg by rounding there). So this vertex could cause an offsetting artefact.

[EdiCojali]

Thanks for your answer. I have solved it by increasing the scale parameter.