Lighting

Lighting refers to all systems in Source which light up a level to make it look realistic. There are many areas of knowledge about lighting that a source level designer should know, most of which are accessible through this page.

Guides

An example of a well-lit room.

• Adding Light - A beginners tutorial on how to set up a basic light entity.
• Intermediate Lighting - A tutorial dealing with all the light sources in more detail.
• Advanced Lighting - Additional information about lighting.
• Constant-Linear-Quadratic Falloff - An easy-to-read explanation of the old C-L-Q light attenuation system.
• HDR - High Dynamic Range Lighting.

Types

Static light sources

 Tip: Static lighting is compiled into Lightmaps, which illuminate brushes and models, and Cubemaps, which provide static reflections. It is free to render, as additional static lights only alter that which is already being processed.

light

A static, omni-directional point light source. (e.g. a naked light bulb or flame.)

light_spot

A static, uni-directional point light source. (e.g. a torch or flashlight) The conical beam angle cannot exceed 90°.

light_environment

Provides two linked light sources:

• A diffuse 'ambient' light (representing reflected light from clouds and the atmosphere in general) that emits from all skybox surfaces
• A directional 'brightness' light (representing sunlight or moonlight) that is only cast in a single direction.

Both are emitted from the toolsskybox material wherever it is used on a map. See also Skybox.

env_particlelight

Illuminates particles produced by env_smokestack. Particles are not affected by normal lighting. Use (no more than) two of these to make (only) env_smokestack particles appear to reflect ambient lighting.

Glowing Textures

Brush surfaces with a light-emitting material (as defined in game_dir/lights.rad) applied will cast volumetric light in a 180° cone.

Static light receivers

Brushes

This Hammer Face Edit Dialog tool 'Lightmap Scale' can be used to control how sharp or diffuse the lightmap of a brush surface will be - an effect most noticeable between areas of high contrast, e.g. shadows. Note that while adding extra light sources will not significantly affect performance, decreasing lightmap scale (i.e. increasing resolution) will more directly increase map file size and memory usage.

prop_static

Unlike other model entities, prop_static are lit statically: a lighting value is stored for every vertex, and the model's collision mesh (or, optionally, reference mesh) is used to calculate lightmap shadows.

There are the following options:

• disableshadows - Do not cast lightmap shadows
• disablevertexlighting - Only store a single lighting value for the entire model
• disableselfshadowing - Prevents the entity from casting shadows on itself
• ignorenormals - Ignores normals of vertex data to calculate lighting. This is extremely useful for foliage, and other thin types of vertex meshes.

Dynamic light sources

 Tip: Dynamic lighting is calculated at runtime, which makes it expensive to render.

env_projectedtexture shines from a doorway.

light_dynamic

A simple, uni-directional dynamic light that can be moved, turned, and adjusted.

point_spotlight

A dynamic spotlight beam effect, with an optional dynamic light source where it hits a surface.

npc_spotlight

A spotlight NPC, similar to point_spotlight but with the capability of tracking targets.

env_projectedtexture

A dynamic light that lights with a texture rather than a solid colour, and which also 'subtracts' realistic dynamic shadows. Affects all surfaces that can accept lighting, and is used for the player flashlight in Episode Two.

Dynamic shadows

 Tip: Dynamic Shadows are cast only by world models (NPCs, phys-props, etc), and only onto brush surfaces (from both Static and Dynamic light sources). They are calculated at runtime, so they are quite crude and relatively expensive to render.

 Warning:  In Left 4 Dead, Portal 2 and Alien Swarm, the direction of a shadow is calculated on a per-entity basis, and dictated by the closest light to the entity. But not in Source2006/2007/2013 mods, unless you apply Dynamic RTT shadow angles in Source 2007 to your mod.

 Warning: Dynamic Shadows can sometimes project through walls and floors, giving away the location of players or objects. Use info_no_dynamic_shadow to workaround this problem if you encounter it.

 Note: Shadows are "cast" by the visual mesh only if there is no shadowlod defined in the QC. Shadow LODs are just low detail meshes used to generate the shadow. These don't apply to shadowmapping (flashlights, env_projectedtexture)

 Note: Dynamic Shadows do not merge with each other or with Lightmaps when they overlap. This can produce undesirable 'doubling up' effects when, for instance, phys props are placed on a phys prop table. You can enable and disable shadows on dynamic entities to work around this.

 Note: Dynamic Shadows support translucency. If your model has varying levels of opacity, it can show up in the shadow as seen here. To do: link broken, find another example

shadow_control

Point entity used to control Dynamic Shadow projections for the entire map, including maximum distance cast, direction cast, and sharpness/diffuseness.

info_no_dynamic_shadow

Point entity used to list Brush surfaces that should not receive Dynamic Shadows.

prop_physics entities 

have a "shadowcastdist" keyvalue to override how far this object casts Dynamic Shadows.

prop_dynamic entities 

have a "disableshadows" keyvalue, and "enableshadows" and "disableshadows" inputs to control Dynamic Shadows cast by them.

NPC entities 

have the prop_dynamic shadow controls, plus a "disablereceiveshadows" To do: to prevent...?

Tyndall effects

Tyndall effects are caused by light scattering on suspended (colloid) particles in a transparent medium. E.g., car headlights in fog.

• Halo (Glow Sprite) effects :

• env_sprite - entity used to create omni-directional glow or flare effects.
• env_lightglow - an asymmetrical glow (for areas of contrasting light).
• env_sun - adds a bright haloed spot to the Skybox to represent the position of the Sun or Moon.

• Lightbeam (Volumetric Light) effects :

• Brush texture : models/effects/vol_light001
• Brush texture : models/effects/vol_light002
• Model : models/Effects/vol_light.mdl - use with prop_static.

• See also Render Modes for sprites, particularly World Space Glow.

Common values

	Brightness
Car Headlights	231 223 192
Combine lamp	147 226 240
Tungsten bulb	254 216 146
Fluorescent tube	159 237 215
Incandescent tube	255 245 145

For values to accompany the stock skybox materials, see Sky List.

Notes

• Naming a light makes it more expensive. Only name lights when you need to. Multiple lights sharing the same name are cheaper than lights with separate names.
• light_dynamic is especially expensive, and will not even show up on some systems
• The basic light entities do not come with a visible representation (e.g. a lightbulb). For that you need a prop. See HL2 light props for a list.
• The basic light entities do not come with a "glow" as you'd expect to see in a foggy or misty area. To provide this, either compile and run the map with HDR enabled, or add a point_spotlight (with dynamic lighting off unless needed) or env_sprite entity.
• Maps will not be lit unless you run vrad (or equivalent). Vrad will not run properly and will not calculate realistic light bounces unless the level is free of leaks.
• Several textures provide their own light & can do so using lights.rad in a mod's directory or the one in sourcesdk/bin.
• Moving brushed-based objects will not change the way they are lit. Their lighting will be calculated only according to their positions in Hammer. (e.g. a brush in a dark room will not become bright if it is brought into a bright room.)
• Light can be reflected off surfaces during compile, indirectly illuminating the environment around them. See $reflectivity

Console commands

mat_fullbright 2. The bright white physics props seem to be a bug; they are lit correctly when in motion.

mat_fullbright <0-2>

0 is normal lighting.

1 is 'full bright' lighting, where everything is 100% lit.

2 has been introduced with the Orange Box and is 'lighting only'. It replaces all textures' images with a colourless monotone, allowing you to see exactly what is lit, where, and probably how.

See also

• HL2 light props
• Color theory (level design)
• Light entities - A list of light entities.
• Intermediate Lighting
• Advanced Lighting
• Window lighting - How to simulate refracted sunlight through openings.

External links

• Understanding and Using Lightmaps (Archived version retrieved on 26 August, 2007)

• Volumetric Lighting (Archived version retrieved on 24 August, 2007)

• Lighting Tutorial - Covers entities & variables with examples (Archived version retrieved on 6 September, 2016)

• Quadratic/Linear/Constant in Lights (Archived version retrieved on 24 November, 2010)

• HDR/Shaped Light/Burning Light/Darkness/Sun/Volumetric (Archived version retrieved on 20 January, 2008)