The light_spot entity allows you to create direct beams of light (like from a flashlight, spotlight, projector, and beacon) rather than spreading light within a radius of 360.
Name (targetname) - Property used to identify entities.
Target (target) - The light will point at this target during compile.
Pitch Yaw Roll (angles) - Sets the pitch (up / down), yaw (left / right) and roll (bank) respectively. The compass in WorldCraft / Hammer corresponds to Yaw. The settings are not always (or not all) used.
ZHLT Fade (_fade) - It darkens the light as the value increases.
ZHLT Falloff (_falloff) - This option can change the normal inverse square falloff of lighting in the direct lighting layer with inverse falloff:
0 = Default
1 = Inverse Linear
2 = inverse Square
Inner Radius (_cone) - The angle of the cone formed around the directional axis. The area inside this cone will contain the brightest light.
Outer Radius (_cone2) - As above, although the area inside this cone will fade increasingly towards the outer edges.
Pitch (pitch) - The pitch of the light (-90 is straight down, 90 is straight up).
Brightness (_light) - The first three 3-digit numbers are the color (RGB). The fourth is the brightness.
Is Sky (_sky) - 0=No, 1=Yes. If Yes, the spot_light will affect the sky brushes, rather than project any light itself.
0 = Normal
1 = Flicker A
2 = Slow, strong pulse
3 = Candle A
4 = Fast strobe
5 = Gentle pulse
6 = Flicker B
7 = Candle B
8 = Candle C
9 = Slow strobe
10 = Fluorescent flicker
11 = Slow pulse, no black
Custom Apperance (pattern) - Use a string of letters to provide a custom light style (see note).
Initially dark (1) - If this is enabled, the entity will need to be triggered to work.
Multisource entities work as light_spot targets.
The Custom Appearance property allows you to enter a string of letters from A to Z, representing brightness. If you entered abcdefghihgfedcba then the light would go from bright to dim and back again and then repeat. Complicating things, to use this feature, you must name the light. However, if you then use a trigger to activate it, then it will behave as a normal light.
Angles above 90 degrees for _cone and _cone2 have no effect. This means that no shadow can be formed beyond the range of 180 degrees (referred by angles/pitch) around this entity.
Glitch: Somehow, the engine (or rad compiler?) opts not to draw the light reflections/bright on the surface of nearby entities (anything 3D other than a brush) when there are SKY textured walls around the light entity. See an example here.
Solution: Create a relatively large block anywhere between the light entity and the sky (usually, er, above the light entity); the "shadow" of this block will delimite where the glitch should be fixed. Apply SKIP texture on all of its faces and a black_HIDDEN on the face parallel to the light entity (usually bottom/top).