light

light is a point entity available in all Source games.

Class hierarchy
CLight ↳CPointEntity ↳CBaseEntity
`lights.cpp`

It creates an invisible static light source that shines in all directions.

Keyvalues

Name (targetname) <string>[ Edit ]: The name that other entities refer to this entity by, via Inputs/Outputs or other keyvalues (e.g. parentname or target).
Also displayed in Hammer's 2D views and Entity Report. See also: Generic Keyvalues, Inputs and Outputs available to all entities

Important:Naming a static light radically changes its behavior. See Naming Lights for details.

~~Entity To Point At (target) <targetname>~~: Deprecated.
Entity to point this light at. Non-functional, as this entity casts light in all directions, regardless of if it has a target; use light_spot instead.

Maximum Distance (_distance) <integer>: This is the distance that light is allowed to cast, in inches. Non-functional in Template:Game link and later, use 50 and 0 percent falloff instead.

Appearance (lightstyle) (style) <integer choices>: Various lightstyle presets. Cannot be used on named lights.; Warning:On modern drivers this will degrade performance by causing frequent stutters. There is no workaround for this other than not using styled lights. The symptoms of this are high spikes in Dynamic Light Rendering when using +showbudget. When toggling r_dynamiclighting off, these spikes will disappear. DXVK is not affected by this problem.

Lightstyle presets (epilepsy warning)
Literal Value	Description	Sequence
0	Normal	m
10	Fluorescent flicker	mmamammmmammamamaaamammma
2	Slow, strong pulse	abcdefghijklmnopqrstuvwxyzyxwvutsrqponmlkjihgfedcba
11	Slow pulse, noblack	abcdefghijklmnopqrrqponmlkjihgfedcba
5	Gentle pulse	jklmnopqrstuvwxyzyxwvutsrqponmlkj
1	Flicker A	mmnmmommommnonmmonqnmmo
6	Flicker B	nmonqnmomnmomomno
3	Candle A	mmmmmaaaaammmmmaaaaaabcdefgabcdefg
7	Candle B	mmmaaaabcdefgmmmmaaaammmaamm
8	Candle C	mmmaaammmaaammmabcdefaaaammmmabcdefmmmaaaa
4	Fast strobe	mamamamamama
9	Slow strobe	aaaaaaaazzzzzzzz
12 !FGD	Underwater light mutation	mmnnmmnnnmmnn

Custom Appearance (pattern) <string>: A string of english letters, like a sequence of piano keys, that define a pattern of brightness. a is 0%, m is 100%, and z is 200%. Updates at 10 Hz. Requires light to have a targetname.

Internal keyvalues used only by VRAD:

Brightness (_light) <color255 + int>: The RGB color of the light, and a multiplicative scalar for brightness (applied after gamma correction). Colors should be between 0 and 255; brightness can be anything (even absent). If only one value is provided, light will be greyscale.; Note:Brightness values below zero are clamped; this can be fixed by modifying VRAD.
Code Fix:In utils/vrad/lightmap.cpp, look for the comment saying "// make sure light is legal", then remove the following if statement, including all its contents.

BrightnessHDR (_lightHDR) <color255 + int>: RGB color and brightness override used in HDR mode. Default is -1 -1 -1 1, which means no change.; Warning:The fourth digit must be positive. Otherwise all light will be sucked out of your map!

BrightnessScaleHDR (_lightHDRscale) <float>: A simple intensity multiplier used when compiling HDR lighting.; Note:Unlike _light and _lightHDR, negative values are supported. Negative brightness will suck out the amount of lighting that the equivalent positive brightness would cast. Use sparingly; set falloff to linear instead of quadratic to make it more like an ordinary shadow and less like a black hole. Since this only applies to HDR mode, it should be reserved for games that don't officially support disabling HDR.

Quadratic (_quadratic_attn) <float>: These three values determine how the intensity of the emitted light falls off over distance. See Constant-Linear-Quadratic Falloff.

0 percent falloff distance (_zero_percent_distance) <float>: Distances at which brightness should have fallen to 50% and (1/256)% respectively. Overrides Linear/Constant/Quadratic parameters if non-zero.; Bug:Using this setting will sometimes not work, which may or may not be related to using the light inside of an instance. Collapsing the instance and messing with the light's falloff values seems to help.

Hard falloff (_hardfalloff) <boolean>: Causes lights to fall to exactly zero beyond the 0% distance. May cause unrealistic lighting if not used carefully.

Cast entity shadows (_castentityshadow) <boolean> (in all games since ) (also in ): Allows the light to modify the direction of nearby render-to-texture shadows so that they always point away from its origin. See also shadow_control.; Note:This keyvalue may not be available in some FGDs.

Shadow cast offset (_shadoworiginoffset) <vector> (in all games since ): A world-space offset that gets applied to the light origin when casting entity shadows. Useful for dealing with funny-looking shadows from very low lights: Just offset up the z axis. Default 0 0 0.; Note:This keyvalue may not be available in some FGDs.

Confirm:How many of the BaseEntity keyvalues even work on static lights? Does parenting work?

Initially dark : [1]: Spawns with the light turned off, so a light switch or similar can turn it on.

SetPattern <stringRedirectInput/string>: Set a custom pattern of light brightness for this light. If the Light is off, then this input appears to turn it on.

FadeToPattern <stringRedirectInput/string>: Fades from first value in old pattern, to first value in the new given pattern. If the Light is off, then this input appears to turn it on.