Automatic mesh generation with QMorph

Quick Guide

This version of Grid3D ships with an implementation of QMorph, a quad mesh generating algorithm.

That means you don't have to create your all-quadrilateral mesh manually anymore but have a tool that does this ugly work for you.

You simply define the boundaries and add edges to them.

The boundaries need not have any particular form, except that they may only consist of SegmentLists with all segments being LineSegments (if you don't know what that means: make sure you don't have circles).

Then you select Coarse Mesh/Quad Mesher/Generate Quad Mesh (QMorph).... This will open up the configuration dialog, which at this point you can safely skip: just click Start Meshing.

Things start off with the creation of an initial triangle mesh in your domain which will then be stepwise morphed into an all-quadrilateral mesh.

The default settings are so that the triangle mesh should be created within a few seconds depending on the size of your domain. Then you should see a window with some statistics about the triangle mesh.

Especially the amount of Mesh Triangles might be interesting for you, since the computation time as well as the amount of quads in the final mesh directly depend on this value:

The amount of quadriliterals in the resulting mesh will be roughly a third of the amount of triangles in the initial mesh.

The time per triangle should be below 10 ms, but for finegrained triangle meshes exceeding 5000 initial elements, the time per triangle might rise above 30 ms.

So it is adviseable to have some rather coarse test runs before trying to generate a very fine quad mesh.

If you think the initial mesh is okay, click the Okay button.

Now the triangle mesh is imported into Grid3D and cloned once to have the original triangle mesh as reference to the resulting quad mesh. If you don't need it, you can safely remove it once the quad mesh is created.

The cloned domain will be changed: in the lower left edge of the Grid3D window you can see a progress bar and the statusbar which display the current state of the algorithm.

Note that after the actual processing of the triangles it still might take some time to smooth and 'proof read' the resulting quadrilateral mesh.

If all went well, you'll end up with an all-quad domain, that you can save. Since the resulting mesh is a normal Grid3D-Domain, of course you can do all the editing and changing you're used to.

Configuration of QMorph

The configuration dialog consists of four tabs named General, Advanced, Triangulation and Internal.

General

This tab contains options everybody should be able to adjust.

Advanced

The options of this tab are a bit more advanced, but still manageable for most users.

Triangulation

Internal

These options are for Qmorph-developers.

If you read the original paper on QMorph, you will know what these are about.

Tips and Traps