Setting up lighting for game scene graphics

Setting Up Lighting for Game Scene Graphics

A scene without functioning lighting is models in a gray room. Well-configured light can elevate even average assets to a level where the player doesn't notice technical compromises. Bad lighting kills expensive models. This isn't about artistic taste—it's about understanding how the engine calculates light.

Where Specifically Everything Breaks Down

In URP projects, the standard mistake is mixing Forward and Deferred Rendering Path without accounting for the fact that Deferred doesn't support MSAA and handles Normal Maps differently on some platforms. Some light sources begin behaving unexpectedly, especially Point Light with low Intensity but large Range—in Forward it falls into the per-object light limit (8 additional lights by default), and on mobile platforms this limit is stricter.

The second classic failure: lighting looks normal in the scene, but after Lightmap baking all shadows shift. This results from incorrect Shadow Bias on Source Light—when Directional Light has Normal Bias above 0.4, static baked shadows don't match dynamic shadows in Mixed mode. Result—"double shadow" at the boundary between baked and realtime.

Scene Light Architecture: From Large to Small

Start with the key light source—Sun/Moon for outdoor scenes, main ceiling light or window for interiors. Directional Light with properly configured Color Temperature and Intensity sets the tone for the entire scene. In HDRP it's more convenient to do this via Physically Based Sky + HDRI Sky to get correct ambient.

Next—back light (rim/back light) for character legibility against the environment. A separate Source Light with small Intensity, directed opposite the main one—the character doesn't blend with the background even in dark zones. In most projects, this light is made invisible to the environment via Light Layers (HDRP) or Culling Mask.

Accent lighting—Point Lights and Spot Lights to create interest in the frame, highlight interactive objects, atmospheric effects. Here it's important to control quantity: each additional source in Forward Rendering adds a pass for each lit object. On mobile devices, 4 additional sources is already a lot.

Working with Color Temperature Instead of Color Presets

Engineers often set the source color directly through Color picker. More correct—via Color Temperature (Kelvin). 2700K gives warm evening incandescent light, 5600K—neutral daylight, 8000K—cold blue overcast sky tone. When changing time of day via Timeline or Shader, it's enough to animate the Kelvin value, and the entire scene changes tone organically, without manual adjustment of each source.

In URP, Color Temperature is enabled via Additional Light Data → Use Color Temperature. In HDRP, this is a standard HD Additional Light Data parameter.

Case Study: Horror Game With Too-Bright Dark Zones

On one horror project, they complained that dark corridors looked "soapy"—soft shadows, no contrast. The problem turned out to be Ambient Light: it was set via Environment Lighting → Source: Color with Intensity 0.8—essentially a full-scene Fill Light. After switching to Source: Gradient with Sky Intensity 0.05, Ground Intensity 0.02 and removing the Equator, dark zones became truly dark, and Light Probes started correctly conveying the difference between lit and unlit zones to the character.

Lighting and LOD: The Problem You Notice Too Late

When using LOD Groups, there's a nuance that regularly surfaces mid-project: light sources with Culling Mask and Light Layers behave differently on different LOD levels only if the Renderers on those levels have different Layer settings. But more often the problem is different—on LOD2 and LOD3 there are often simplified Meshes without Normal Map, but the same shader as LOD0. As a result, LOD switching causes sudden lighting changes: the normal model has beautiful highlights, while the simplified lod model looks flat.

The correct approach: for LOD2+ use simplified shaders (Lit → Simple Lit or Custom Unlit with baked AO), not the full PBR stack. This is not only visually more correct but also reduces GPU load when rendering distant objects.

Another point with Emissive materials in Baked GI: an object with Emissive can "bake" its glow into surrounding lightmaps, but only if it has Contribute GI enabled and the Emission parameter in the shader is passed to Lightmap Emissive. In URP/Lit this is Emission → Baked Emission. If this flag isn't enabled, the object glows by itself but illuminates nothing in the baked lightmap—a common reason why a "glowing" screen or window doesn't cast light on the floor around it.

Tools for Lighting Diagnostics

Frame Debugger (Window → Analysis → Frame Debugger) lets you step through each draw call and see which Pass is responsible for a specific object. Invaluable when you need to understand why an object lights differently than expected.

Rendering Debugger in mode Lighting → Albedo / Specular / Normal / Direct Diffuse breaks lighting into components. If a Normal map doesn't influence lighting as it should—it's immediately visible in Normal view mode.

GPU Usage Profiler shows how much GPU time goes to Shadow Caster Pass for each source. If a single Spot Light with Shadow Casting enabled consumes 3 ms—this is reason to either lower Shadow Resolution for that source or switch it to non-shadow mode and simulate shadow via Blob Shadow texture.

For HDRP projects there's a separate tool—Light Explorer (Window → Rendering → Light Explorer). Shows all light sources in the scene as a table with modes, intensity, and shadow types. Convenient for auditing scenes with 20+ sources: no need to click on each in Hierarchy.

Process and Timeline

Work begins with an art brief: references, time of day, atmosphere, target platform. Next—technical audit of the scene (number of sources, current Render Path, engine version). Then basic lighting setup with iterative agreement. Final stage—optimization and verification on target devices.

Cost is calculated individually after analyzing requirements and current project state.