light_directional
From Valve Developer Community
light_directional is an internal point entity available in all Source games since Left 4 Dead. It is a directional light with no falloff, similar to the direct lighting of light_environment.
Note:As with a light_environment, a light_directional is only emitted from geometry covered with the skybox tool texture.
Bug: 
In Counter-Strike: Global Offensive, after the Wildfire update, this entity does not seem to be working properly or has to be set differently. It can create excessively dark shadows tinged with the color of the light_environment ambient color plus the setting of the light_directional. It appears to boost these colors tremendously now.Keyvalues
- Pitch
<integer> - The downward pitch of the light from the sun. 0 is horizontal, -90 is straight down.
- Brightness
<color255> - The RGB color and brightness of the light. Colors must be between 0 and 255; brightness can be anything.
- BrightnessHDR
<color255> - 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
<float> - Amount to scale the light by when compiling for HDR.
- SpreadAngle
<float> - The angular extent of the light for casting soft shadows. Higher numbers are more diffuse. 5 is a good starting value.
Angles:
- Pitch Yaw Roll (Y Z X)
<angle> - This entity's orientation in the world. Pitch is rotation around the Y axis, yaw is the rotation around the Z axis, roll is the rotation around the X axis.
