Build flush
Make sure that your brushes fit tightly together. Brushes should abut against one another. Avoid seams created by the edges of two brushes, as these junctions may result in leaks. Instead, drag one or the other brush the extra units to create an abutment. For example, take two bricks and hold them so that they are joined only by their corners. Obviously, this configuration is pretty unstable. Now slide one brick down so that its base is flush against the surface of the other. This is the configuration you should use.

By the same token, try not to overlap brushes. In other words, avoid having one brush intersect with another. If a brush is sticking into another brush, the processor will have to do more work to figure out which geometry to remove.

It is especially important to avoid allowing two overlapping brushes to share a surface visible from inside the world. The simplest example is a brush that is copied and pasted onto itself. If the two brushes have the same texture, you can expect lighting errors at the very least. If the brushes have different textures, you may see both lighting errors and z-buffering issues (shimmering resulting from the different surfaces being rendered in different frames).

Use the locator
By moving the locator (the green lines that crisscross each window in DEdit) with the X key, you can move the world origin, which is the junction where x, y, and z meet. This tactic allows you to place new brushes precisely where you want them.

The principle is fairly simple.

Typically, you will create brushes in one of the three perspective windows: x/z (top/bottom), x/y (front/back), or y/z (left/right). If you build a brush in the x/z window, it will appear in the world where the y axis meets x and z (0 0 0 by default). Likewise, if you build a brush in the x/y window, it will appear where the z axis meets x/y.

If you move the locator up by 128 units in either the y/z or x/y windows, you can change the y position at which brushes created in the x/z window will appear.

Tutorial: Create a new world in DEdit. Create a new 256x256 brush in the upper right window (x/z). Give it a thickness of 32 units. You now have a floor.

In the x/y window, raise the locator so that it is 128 units above 0 0 0. Return to the x/z window and reduce the grid to 32x32. Along the top edge of your floor, create a new brush that is 256x32. Give it a thickness of 160. You now have a 128 unit tall wall that is flush against the floor of your room. Repeat the process along the other edges of the floor (make the brush 32x320x160 to ensure that it is flush against the north and south walls).

Return to the x/y window and raise the locator another 32 units. In the x/z window, create a new brush that encompasses the outer edges of the walls (it should be 320x320 units). Give it a thickness of 32. You now have a roof that sits snugly on top of your walls.

To build this room without the locator, you would have to create your brushes along the default axes and then drag them into place. In a large level, it quickly becomes a time-consuming process.

Note that the locator also defines the center of rotation used whenever you rotate brushes.

Build brushes in all three perspective windows
Don't just build brushes from the top down view. If you want a sloped ceiling, use either the x/y window or the z/y window and create the exact slope you want in one simple step. Use the locator so that it aligns with the edge of the room.

Start simple and save detail until last
You can save yourself lots of headaches by constructing your world in simple pieces. Start with floors and stairways, making sure you have plenty of room for walls and other architecture. You may even want to consider building the entire floorplan of the level before you build a single wall. That way you can run around in it and get a feel for the layout without having to commit a lot of time and energy to details you may end up chopping out anyway.

Note that you'll need to enter "forceclear 1" at the console in an unenclosed level in order to get rid of the hall-of-mirrors (HOM) effect.

Build up your rooms as boxes, making sure the areas are big enough (it's easy to make an area smaller, but expanding a tight corridor can be a pain in the ass in a complicated level). Once you've got a nice boxy layout, seal it up by tracking down any leaks and do a Full Optimization on it..

Check your poly counts at this point, as any performance issues you notice at this early stage will only get worse as you start to add detail.

Once you're comfortable with the layout, you can go into your individual rooms and start adding the sloped ceilings, light fixtures, pipes, and whatever else you're planning. You'll probably find that you've got tons of ideas after having run around in the boxy shell for a while.

Group brushes as you go
You may find it helpful to group individual areas so that you can hide them easily (right click on a node in the Node View and select Hide). I tend to group an area's floors separately from its walls and ceilings.

It's particularly advisable to group light fixtures, railings, and other detail brushes and name the nodes accordingly. For one thing, these brushes will be excellent candidates for a detail setting of 1, which will dramatically speed up optimization time. For another, detail brushes tend to be distracting when you're working on a large level. Hiding as much as possible makes it easier to see what you're working on and reduces the likelihood that you will inadvertently mess something up.

Take advantage of the tools
DEdit lets you create brushes of all shapes and sizes with a few simple clicks. While you should be careful of concave brushes, you should exploit the editor's flexibility to save yourself time. If you're not using all three perspective windows frequently, you're probably not working as efficiently as possible.

If you want to create an archway, line up the locator so that the brushes you create will fall where you want them, then create the archway out of small, angled convex brushes. You can even create the entire archway out of one concave brush and use it as a template for the individual convex brushes. Just be sure to delete the concave brush afterward (use Find Concave Brushes in the World pulldown menu to select any concave brushes you've created).

Likewise, you can save time by building half the archway. Select the brushes, copy and paste them, and rotate them to complete the archway.

Aesthetic tips
There are some simple tried and true tricks you can do to improve the look of a level:

• Vary ceiling and floor heights in adjacent areas
• Use lots of angles
• Take advantage of 3D with multilayered areas
• Use skylights to create a more open feel in an area