Naming Lights

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Giving a light entity a targetname makes VRAD compile a second lightmap "page" for the surfaces that its emitted light touches. This won't harm in-game performance, but it will increase compile time and BSP filesize, regardless of whether the light ever receives input to change its state.

However, the system can be overloaded if you try to make it handle a large number of overlapping named lights (since the number of pages needed increases exponentially). When this happens performance can be harmed and you may well see lighting anomalies.

VRAD attempts to avoid this with its hard-coded limits of two switchable lights affecting a brush face and 32 pages in total. More than this causes VRAD to throw a warning such as "Too many light styles on a face" and refuse to compute the lightmaps for those lights; this will make those areas appear as if they are not lit. You can help too by giving lights that will always change state at the same time a shared targetname, which makes VRAD merge their pages together.

Note:To reduce the number of pages created, light from named light entities is direct and won't bounce between surfaces. This can look very crude!
Warning:There is a bug in the Left 4 Dead 1 engine that affect the use of named lights. A named light, even if totally still will be considered fully dynamic by the engine and pump up a large chunk of frames per second until it is turned off and on for the first time. The workaround is to set the light to start turned off and to turn it on on map spawn using a logic_auto entity for instance. This could also affect Left 4 Dead 2, but this has not been proven.

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