Developing lighting schemes and color keys for graphics

Developing Lighting Schemes and Color Keys for Graphics

A colour key is not a beautiful picture for presentation. It is a technical document that determines how many iterations the environment will go through before final approval. If it doesn't exist or is made as a rough sketch in Photoshop without reference to real brightness ranges, environment artists work blind: each asset gets painted according to their own understanding of light, and the final scene assembly looks like it was compiled from five different games.

A lighting scheme is not "where the sun shines from." It is clear documentation: the direction of the key light source, the tonal range of shadows and highlights, the color temperature of the fill light, the acceptable contrast between zones. Without this, neither Enlighten nor Progressive Lightmapper can save the final render from becoming a muddy mess.

Where the Process Breaks Down Without a Colour Key

The most common situation: the art director approves a concept with an atmospheric blue sunset, environment artists create a level, the technical artist sets up the Directional Light in Unity HDRP, and everything looks "wrong." Iterations begin on normals, re-lighting assets, changing the Skybox. Three weeks lost.

The reason is almost always the same: the colour key was made as an illustration, not as a technical reference. It did not specify:

• Normalized Exposure values in EV100 for key zones
• Color temperature in Kelvin for each source (for example, 5500K for daytime sun versus 2800K for torches in dungeons)
• Ambient occlusion level in shadowed zones — without this, artists arbitrarily increase AO intensity and get mud instead of atmosphere

The second problem is the absence of a lighting scheme for different times of day or gameplay situations. In an open-world project with a day/night cycle, a colour key is needed for a minimum of three states: day, golden hour, night. Each one with separate values for Light Probe intensity and sky irradiance.

When there is no scheme, the Level Designer simply tweaks parameters by hand and hopes it will look "nice." This works once in five.

How a Technically Correct Colour Key is Built

The foundation is the link between visual representation and real values in the engine. A colour key is made in two layers: artistic (color and light composition, readability of silhouettes, emotional tone) and technical (specific values for implementation).

The artistic layer is created in Photoshop or Procreate — quick sketches on a blocked-out scene geometry. Here you determine: where is the brightest spot in the frame, where the player's eye goes, how saturated the ambient is versus direct light. At this stage, visual literacy is important — works by Seiji Yamamoto on lighting, lighting bibles from GDC presentations on God of War or Horizon Zero Dawn give an understanding of what works.

The technical layer is translating artistic solutions into parameters. For Unity HDRP:

• Directional Light Intensity in Lux (for a daytime scene — 80,000–100,000 Lux, for overcast — 10,000–20,000)
• Sky and Fog Volume settings: Fog Attenuation Distance affects the readability of distant objects no less than fog in the literal sense
• Light Probe Proxy Volume for objects with non-standard geometry
• Reflection Probe resolution — 256 is sufficient in open spaces, 512 minimum inside rooms

For Unreal Engine 5 — Lumen gives different logic: the colour key must account for indirect lighting changing dynamically. Therefore, static colour keys for Lumen projects are supplemented with a specification of the acceptable brightness variance range — how much the final render can deviate from the reference when the light source position changes.

In practice: in one project with a tiled dungeon, a lighting scheme was created for three zones — entrance (transition brightness), depths (minimal ambient, accent point sources), boss arena (high contrast, red fill). Each zone has a separate colour key with EV100, source temperature, and allowable deviation in Lux specified. Environment artists worked from these documents without additional approvals. The final assembly passed approval on the first try.

Tools and Documentation Formats

A colour key in a modern pipeline is not just a JPG. The final document includes:

• Reference sheet in PSD with marks of brightness zones (Levels/Curves as visual annotations)
• Lighting spec — a table with source parameters: type, intensity, temperature, shadows resolution
• Gradient map — demonstration of the tonal range from darkest shadow to brightest highlight
• Thumbnail grid — 6–9 variations with different moods, from which the final direction is chosen

For animation projects with cutscenes, a lighting timeline is added — frame-by-frame documentation of lighting changes at key events. Without it, technical artists start lighting cutscenes from scratch each time instead of working to a unified standard.

Stages of Work on a Lighting Scheme

The process is standard, but its scope depends heavily on the scale of the project.

We start with a briefing: analyze existing concepts, gameplay materials, technical platform constraints. Next comes iteration on the thumbnail grid, direction approval, detailed development, and final documentation with technical parameters.

Cost is calculated after analyzing the scope: number of locations, lighting states, target engine, and requirements for technical detail in the documentation.