Making the grid
The grid section of the MappingMeshTool can be seen below:
Using these controls you can generate a grid of points in the axes. When
you are ready to draw your subdomains, mouse clicks in the axes will snap to grid points.
Either use the defualt values given for the six controls here, or choose your own x and y ranges and
the grid spacing in each direction. If you make the grid points too densely
packed (i.e. you make X spacing or Y spacing too small) it will be difficult
to use the mouse to select your desired vertex positions. If your domain will have all vertices at regular coordinates,
make sure grid points exist at each of your planned vertex locations in order to make drawing the domain easier.
It is a good idea to make the grid cover the total eventual size of your
domain.
After entering all of the values, click the Make Grid button. This will draw the grid in the axes and make the Click SD Points (see Drawing a subdomain) button visible. If you need to change the grid later during mesh generation, it may corrupt the image in the axes, but any subdomains you have already defined should not be affected.
Using the grid is optional. If you plan on using the mouse to select vertex location in the axes, it is required. However, if you will instead be entering the vertex locations in the edit boxes, the grid is not necessary.