# 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 – ZaMoC Apr 23 '17 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? – space bobcat Apr 23 '17 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}. – bill s Apr 23 '17 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). – space bobcat Apr 23 '17 at 22:14
• This is a bug and you should report it to WRI. – user21 Apr 25 '17 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. – Michael E2 Apr 24 '17 at 10:44