Patch-Mesh 101
Simple Mesh Terrain 

Now texture the sides and put some water in the pool.
Select a water texture (I'm using liquids/clear_ripple1) and create a brush the same size as the pool. The top face should be 8 units lower than the surrounding floor.

Now make another brush out of some suitable texture (I used stone/pjrock21) the same size as the pool. Switch to the XY top view and turn the brush into a simple patch mesh. Curve menu then Simple Patch Mesh.
Let's make the width 9 and the height 9.

Turn on vertex editing. (the V key)
If any points are off the grid hit ctrl-G to snap them to the grid.
Select the point in the XY top view by clicking on it. (You can also left click and drag the mouse which will create a blue box that you can use to select one or more vertices at a time.) I move the selected vertex over a little before switching to one of the side views to move the point. Then I put in back in straight row in the XY top view (I know it seems like more steps this way but It works for me.)

My side view of this mesh.

Now if you want to select all the points in a row hold down the shift key and left click on a point in the XY top view. Notice how it selects all the points in that row and then on the next click all the points that cross that point in the other row. (Try it - you will see what I mean.)
You can also select all vertex points in a row in the x or y view.
This is what we did in the last page but the mesh was on its side so we used the XY top view then.

Move all the points that you want.
Looks like this in the game.

You can use these meshes for all kinds of things such as walls, ceilings, floors and even details.
What next? I know, let's make a hole in the ceiling to another level and trim it with an inverted cylinder.

Simple patch mesh page 5