Optics is a map I created for a HL2World.com limited resources mapping challenge in 2007. The challenge: build a nice looking scene using only one light. Nothing else to provide illumination, just a single light entity. We only had to submit a screenshot, so this is not meant to have any gameplay. The community response was very favorable. Most were shocked and couldn't believe it until I explained how it was done.

The screenshot

This is the screenshot I submitted:


How it's done

Again, the whole challenge was to light a map with only one light. Looking at the screenshot, you might be skeptical and think there are light_spots, dynamic lights, a light_environment, texture overlays, or other cheats. Nope. It's real RAD light that all comes from one single light entity.

The trick is dev_reflectivity textures. These textures do not create any light; they simply reflect more light than a standard texture. One light is buried deep underground, and light comes up through a number of reflective light tunnels. This is the same principle used by fiber-optic technology, hence why the map is named Optics.

Here's how the reflective tunnels light the map. The tunnels comes up from underground and then shoot light down from overhead:


The giant box on the left essentially acts as a light_environment:


Most of the light comes up through 6 main light tunnels, and is then split off into smaller tunnels for each light. It took a painstaking amount of effort to get each light perfect. The light underground is so extremely bright that it turns everything black. In addition to directing light where it needs to go, the tunnels help reduce the light brightness down to a warm, usable light. Each tunnel's length and width had to be carefully adjusted to get this desirable light.

I did run across a few problems:

  • Models get lit incorrectly at fullbright or solid black. So I couldn't use models for anything important. Take note of the brush light poles. Even those trees are just a convincingly placed textured brush.
  • Displacements get lit poorly. I had to cover some ugly displacement areas with brushes.

Download, install, and play

There is no actual gameplay, but it might be cool to have a look around. Let me know if you want the map's .vmf source.


This is meant for HL2 Single Player. Place .bsp file in \SteamApps\accountname\half-life 2\hl2\maps\.

To play, open your console and type: map optics

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