Optimization/Level Design

It's easy to create a map that older (or even newer!) computers will struggle to draw at sixty frames per second. This article is the hub for all information on how to to prevent that by optimizing your map.

Areas

Leaks

There's no excuse! Leaks will invalidate almost all of your efforts elsewhere.

Visibility

Reducing the number of surfaces and objects that are drawn in the first place. The single most important area.

Physics

Various tricks to avoid overloading the CPU with physics calculations.

Materials

Correct material choices will allow your map to scale down its demands on slower computers.

Lighting

Performance and file-size optimisation.

Skybox

A properly optimized skybox will significantly reduce lag and map size

Commands

There are many more useful console commands than the ones listed here — find them in their relevant articles.

Note:Most performance-related commands require sv_cheats.

cl_showfps

A simple output of framerate. 1 is real-time, 2 is averaged over the past second.

showbudget

A panel which displays how your computer is spending its budget for each frame. It's the premier tool for working out exactly what's sucking up performance in your map.

It's invoked with +showbudget and -showbudget, which means that you can bind the former to a key (i.e. bind <key> +showbudget) and it will only appear when you hold that button down.

mat_wireframe

A console variable that lets you see through walls. This way, you can see exactly what is being drawn - for reasons described in visibility optimization, often more than you might think is sensible.

There are three wireframe modes, 1 through to 3, which display the information you need with progressively fewer lines.

Another great site for more on map optimization in half-life 2 is Ralph van Hoorn's website