# How to make a region smoother

Bug introduced in 11.0 and persisting through 11.1.1

In the tutorial Solving PDE with Finite Elements at the documentation center, there is this code:

Ω =
ImplicitRegion[! ((x - 5)^2 + (y - 5)^2 <= 3^2), {{x, 0, 5}, {y, 0,
10}}];
RegionPlot[Ω, AspectRatio -> Automatic]


This is supposed to look like this: But when I run the same code on my Mathematica 10.3, I get this: What is going on? How to make it just like it is given in the documentation center? I guess there is a precision setup?

Update: I ran this code in Wolfram Programming Lab online and the problem is the same. Also, I updated to Mathematica 11.1. The problem is still there.

• looks ok on mathematica 10.4 Apr 23, 2017 at 21:51
• @Jenny_mathy, I just ran it on Mathematica 11 and I still have the same problem. It is probably not version dependent at this point. Any ideas? Apr 23, 2017 at 21:59
• I get the same issue (Mac/MMa 11.1). Oddly, the problem goes away if you plot from {y, -3, 13} but shows oddities on both sides if you plot from {y, -2, 12}. Apr 23, 2017 at 22:00
• @bills, this bug gives me trouble with solving a Laplace equation over a region with a circular part that I made using "Disk". It is the post from yesterday link. I see that if I make a "Disk", it is not nearly as smooth as I would want it to be (or as it is shown in tutorials). Apr 23, 2017 at 22:14
• This is a bug and you should report it to WRI. Apr 25, 2017 at 13:36

RegionPlot[DiscretizeRegion@Ω, AspectRatio -> Automatic] • @ViacheslavPlotnikov Yes, I wondered if plotting was the main concern. For plotting and geometrical applications, DiscretizeRegion is a typical top-level function. For NDSolve and the finite-element-method, ToElementMesh and related functions in the NDSolveFEM  context allow better control over setting up PDEs. The easiest way is probably the options "MeshOptions" and MashCellMeasure, but other ways exist. Apr 24, 2017 at 10:44