OK, so you've cleaned up your level, no map holes, no spatial fluxations, no annoying salesman, etc. etc.

Then you fire up the level. Wham. Mucho problemo. It runs slower than a turtle in molases on a cold day (Or something slow like that). Now, we need to stop that because if that level is running slowly, you have a big problem. It is not a candidate for release in this state.

But before we go into this, we need to know the rudimentaries of CPU Usage.

Ok, firstly, you have Memory. DRAM, RAM, etc. etc. This is where the CPU performs all of its equations, calculations, processes etc. Understand the difference between Hard Drive Space and Memory. Completely different things. Hard Drive space is for storage of file data, for a long period (Of course, there are some files you want to get rid of pretty quickly, but this still counts as "Long Period"). Operations in Memory are kept there only as long as the computer is turned on, or less. This is only kept for a "Short Period".

Memory is a very limited resource. A usual ammount of Memory is 64-128 MB. My computer has 256 MB, but that's because some of my computer's hardware requires that much to run properly, and because I need a lot of it to use my ADSL link (And also because it makes games run faster, and because me and Dad agreed on it). But this is all beside the point. Memory is a fixed resource. You never have more or less than what is put inside the computer.

The less memory you have free, the longer it takes for computers to do their equations. This makes framerates and game performance lower. The more you have free, the better things will run.

But there is a problem with the game systems of the Unreal Engine (Which Deus Ex uses). After using system resources, it doesn't give them back until you restart the computer. Neither does UnrealEd or DXEd. So, you want to use as little system resources as possible.

One thing that REALLY messes up game performance is large mirrors. Locate a file called dxmp_mcramos.dx and you'll know what I'm talking about. It has an enormous spherical mirror in the middle of it, which reflects and refracts every single movement in the whole map except for in the towers. This lags the map editor, let alone the game. So large mirrors in large open spaces are a no-no.

Another thing that hogs system resources is fully solid objects. These are the blue-outlined brushes in your wireframe views. They take more system resources then semisolid ones. Note that the rumour of players clipping through semisolid brushes is just a myth. They act exactly like fullsolid brushes except they take up less shapes. However, certain shapes should not be made semisolid.

Intricate or complicated brushes like fluted columns or french curly roof supports are things you want to be semisolid. Crates and large structural brushes which are cuboid, spherical or prism-shaped should NOT be made semisolid. At all. Fancy shapes like rock formations, small geometric shapes, holographic brushes, mover templates and floor-lofter creations are all excellent subjects for semisolidness.

Another thing that hogs CPU space is lots of actors on screen at once. If you have tons of people in one room, try to make sure they're not all in view all the time. Try to hide some of them behind barriers, hedges, trees, doors etc. or you'll lag out the level. However, not filling a room enough can make it look bland and uninteresting. So try to be careful about keeping the balance.

Remember to do a rebuild after fixing up these points. And if you want the system resources back after playing DX and DXEd, I'm afraid the only way is to restart the computer you've used them on.