Lesson 10 gave you detection UI that players can read at a glance. Lesson 11 made sound honest. This lesson is about sight in the world: exposure, shadows, and global illumination choices so Lesson 5 sight checks and player intuition agree when someone is hidden in plain view versus actually hard to see.

Lesson objective

By the end of this lesson you will have:

1. A locked exposure baseline (manual or Post Process Volume) so Lumen bounce does not pump brightness when the player turns or enters new rooms.
2. Sightline tests at worst-case angles from Lesson 3 cover spots: player silhouette vs background contrast documented with screenshots or notes.
3. Post-process and lighting priorities that preserve HUD and stinger readability—no crushed blacks that hide UI, no blooming that washes out objective markers.

Step 1: Separate “cinematic mood” from “stealth legibility”

Stealth needs predictable visibility. Before touching sliders, write three rules for your slice:

Pro tip: If your trailer wants orange grade and your gameplay wants cool readability, use two Post Process Volumes with priority and blend—gameplay volume wins in mission bounds.

Step 2: Exposure lock (stop auto-ISO from lying)

1. Add or select a Post Process Volume that covers your mission playable bounds (Infinite Extent off if you want menu different from level).
2. Under Exposure, switch from fully automatic to metering you control: Min / Max Brightness tightened, or Exposure Compensation fixed after one reference pass.
3. Place a neutral grey reference card or debug plane in key rooms; adjust EV until mid-grey reads mid-grey on your target display without HDR wild swings.

Gameplay note: Interior → exterior transition is where Lumen often blows highlights. Use priority volumes at doorways or lower emissive props near thresholds so perception tests from Lesson 5 stay stable.

Step 3: Key, fill, and rim for stealth (not just beauty)

1. Key from a direction that models faces and weapons guards need to read—usually slightly off-axis from primary player approach.
2. Fill soft enough that shadow-side cover is not pure black unless intentional puzzle darkness.
3. Rim or back light on patrol lanes so moving silhouettes pop against busy backgrounds (pipes, foliage cards, neon props).

Cross-check with Lesson 4—if crouch speed is quiet, lighting should still sell risk when you cross a lit strip.

Step 4: Lumen budgets that keep frame time and contrast

1. Reduce emissive noise on large surfaces; Lumen will bounce that color everywhere and flatten contrast.
2. Card or proxy foliage carefully—too many thin occluders can flicker GI and break sightline trust.
3. Run r.Lumen.ScreenProbeGather.Temporal and related quality cvars only after look locks; stability beats extra bounce for competitive readability.

Pro tip: Reflections on wet floors are cool but can duplicate enemy silhouettes. Tune roughness or reflection intensity if players mis-read count.

Step 5: Post-process stack audit (contrast, UI, colorblind)

1. Color grading LUT: lift shadows slightly if Lesson 10 meters use dark themes—WCAG-style contrast checks on text over world.
2. Bloom and lens dirt: lower threshold or intensity until objective icons and suspicion ticks do not compete with blooms around lamps.
3. Motion blur and depth of field: off or minimal for slice capture; they hide micro tells stealth players rely on.

Step 6: Worst-case sightline pass (document, do not guess)

1. List five positions where design says “should be risky” (long hall, backlit window, under spotlight).
2. For each, capture player from guard eye height (use debug camera or PIE view target).
3. Annotate: silhouette score 1–5, fix if below 3 (add rim, darken backdrop, move prop).

Critical: Re-run one Lesson 5 sight debug draw after lighting changes. If traces hit but players feel blind, lighting still owes clarity.

Mini challenge

1. Stand in deepest shadow in your main objective room—HUD detection meter and world read should agree within one tier.
2. Toggle exposure auto vs locked—confirm AI sight success rate does not change wildly on same route (if it does, perception is fighting tonemapper).
3. Capture before/after one post change affecting shadows—verify footstep VFX or interaction prompts from earlier lessons still pop.

Troubleshooting

Summary

• Exposure lock keeps perception and player trust aligned across rooms.
• Lumen is a gameplay system here: contrast and stability beat showreel bounce.
• Post last—after lights tell the truth—and always check HUD and audio cues on top.

Further reading

• Materials and lighting in Unreal — directional setup, GI, and post context for readability passes.
• Unreal audio cues and attenuation guide — keep Lesson 11 mix stable after bright stingers or flash VFX.

FAQ

Do I need Path Tracing for a vertical slice?
No. Lumen with controlled emissive and exposure is enough; path trace is for beauty shots, not iteration speed.

Should night missions be mostly blue?
Color cast is fine if luminance separation stays strong. Blue on blue silhouettes fail faster than neutral grey scenes.

What if I use stylized toon shading later?
Keep this lesson’s sightline notes; toon ramps replace smooth falloff but still need predictable tiers for stealth.

Next: Lesson 13: Performance Optimization Pass is the performance pass—Stat unit, GPU visualize, and budget Lumen/Nanite so the look you locked here still hits your frame target in a packaged build. Finish Lesson 12 when worst-case screenshots and perception debug agree on fair visibility.