Exercise: lighting one scene four ways

Lighting one scene four ways means taking a single finished environment and relighting it into four different moods, times or functions, while every mesh and material stays the same. It isolates lighting as a skill: if a version looks wrong, the lights, sky, fog or exposure are the only things that can be at fault.

Lighting has a large effect on how an environment piece reads. Naughty Dog lighting artist Gabe Betancourt puts the first rule simply: "The key light is master" (80 Level: Learning Lighting for Video Games). This brief makes you practise that rule four times.

#The brief

Goal. Light one small scene in four versions and present them side by side from the same cameras:

• A. Midday sun: a high directional sun plus sky.
• B. Overcast: no direct sun; the sky is the key.
• C. Night with practical lights: lamps, screens or fire that exist in the scene, plus faint moonlight.
• D. Low evening sun: a low, warm key with long shadows.

The scene. Use the room from exercise: a modular room, or any interior of roughly that size with at least one window, one doorway and a few props. A space with both inside and outside visible is ideal, because it forces you to handle exposure.

#Constraints

#Stages

#1. Scene preparation

Check the albedo before you touch a light. The Level Design Book notes that shadows which look too dark after a bake are often caused by dark albedo textures, not weak lights (The Level Design Book: Lighting). Robert Yang's GDC 2018 workshop advises you to "err on the side of brighter albedos near the upper midtone range of a histogram" (Radiator Design Blog: GDC 2018: How To Light A Level, slides and…). Fix any very dark base colours now (base colour (albedo) map, physically based rendering), or every version will fight them.

Set up the three cameras with sensible lenses and lock exposure to a manual value.

#2. Reference and a one-light test

For each version, find one reference photo or film frame. Betancourt's method is to match it with a single light before adding anything else (80 Level: Learning Lighting for Video Games). Write one sentence per version describing the mood and the focal point it should push.

#3. Key light

Build the key: its angle, colour, intensity and shadow shape. Betancourt says that if you keep at the key "until it has what you're looking for, 80% of the work is laid-out"; if a scene goes muddy, delete the lights and restart from the key (80 Level: Learning Lighting for Video Games). Let global illumination provide the bounce. See light and shadow and value.

#4. Fill, practicals and gameplay

Add only what the key cannot do. The Level Design Book works in passes: global lights first, then wayfinding and the critical path, then gameplay, then detail and mood (The Level Design Book: Lighting). Its wayfinding rule fits every version: "Big important exits should have more important looking lighting" (The Level Design Book: Lighting). Yang's version is to keep a hierarchy: "Don't light everything the same, but rather, create some differentiation" (Radiator Design Blog: GDC 2018: How To Light A Level, slides and…).

For version C, every light should be motivated: The Level Design Book defines a motivated light as "a light source with a plausible fixture", and notes that one visible fixture may drive several invisible engine lights (The Level Design Book: Lighting). See wayfinding and emissive materials.

#5. Atmosphere and grade

Add fog, sky and post-processing last, and keep them subtle. Turn auto exposure on with a Min and Max EV100 range that fits the version, and set up local exposure if you use Lumen: Epic says it "should always be set up when using Lumen Global Illumination" (Unreal Engine Documentation: Auto Exposure). See tonemapping and colour grading and LUTs.

#6. Profiling

Record GPU frame time and the number of shadowed lights for every version. Fortnite's Chapter 4 targeted 60 fps on consoles and gave dynamic global illumination and reflections "four milliseconds" combined (Unreal Engine tech blog: Lumen brings real-time global illumination to…). You do not need to hit a console budget, but you should know which version is most expensive and why.

#Presentation

Show the same camera in all four versions in a grid, then each version alone. Add a short note per version (key light, fill, mood) and the profiling table. A lighting artist's breakdown is about decisions, so the notes matter as much as the pictures. See making (and reading) an art breakdown and demo reels and flythroughs for a short camera move through the best version.

#Shipped lighting work to study

• Two lightings of one level. Brian Mullen, lead lighting artist at Insomniac Games, shows his lighting of the Sargasso level in Ratchet and Clank: Rift Apart, covering the first visit and the return "war" version, including the sky texture, atmosphere, volumetric clouds and colour grading for both (ArtStation: Ratchet and Clank: Rift Apart - Lighting…). It is the same exercise at shipped quality.
• A lighting budget in a live game. Epic's write-up of Lumen in Fortnite Chapter 4 explains the 4 ms budget, why the game went dynamic, and the deliberate cheats for indoor areas (Unreal Engine tech blog: Lumen brings real-time global illumination to…).
• A Naughty Dog lighter's process. Gabe Betancourt's 80 Level interview covers starting lighting in mid pre-production, the hue pass on blockout colours, the key light, and lightmaps versus vertex baking (80 Level: Learning Lighting for Video Games).
• A level designer's lighting workflow. Robert Yang's GDC 2018 workshop transcript walks from graybox through global lights, progression and set pieces (Radiator Design Blog: GDC 2018: How To Light A Level, slides and…).

#Further reading and watching

• real-time lighting, baked vs. dynamic lighting and exposure and post-processing: the theory behind this brief.