Baked Lightmaps vs Real-Time Global Illumination

Choosing between baked lightmaps and fully real-time global illumination (GI) is a foundational decision in game development that directly impacts a game’s visual fidelity, performance, and production pipeline. While baked lightmaps offer highly detailed, pre-calculated static lighting with almost zero runtime performance cost, real-time GI enables dynamic, shifting environments at the expense of significant hardware resources. This article examines the key factors—including target hardware, game mechanics, memory limitations, and development workflows—that dictate which lighting method is best suited for your game.

Target Hardware and Performance Budgets

The computational power of your target platform is the most critical factor in choosing a lighting solution.

• Baked Lightmaps: Because the complex math of light bounces, shadows, and ambient occlusion is calculated beforehand and saved into textures, baked lighting requires very little processing power at runtime. This makes it the industry standard for mobile devices, standalone VR headsets (like the Meta Quest), and older console generations.
• Real-Time Global Illumination: Technologies like Unreal Engine’s Lumen, ray-traced GI, or screen-space global illumination require powerful, modern GPUs. If your game targets high-end PCs and current-generation consoles (PlayStation 5, Xbox Series X), you can leverage real-time GI to achieve realistic, interactive lighting.

Environmental Dynamism and Gameplay Mechanics

The level of interactivity in your game design heavily influences your lighting choice.

• Static Environments: If your game features fixed levels, static geometry, and a constant time of day (such as a linear horror game or a competitive indoor shooter), baked lightmaps are ideal. They provide photo-realistic indirect lighting and soft shadows that do not need to change during gameplay.
• Dynamic Environments: If your game features a dynamic day/night cycle, destructible environments, player-built structures, or moving light sources that affect the entire scene, baked lightmaps cannot be used. Real-time GI is required to update the bounce lighting and shadows dynamically as the world changes.

Memory and Storage Constraints

Lighting solutions impact system memory (VRAM) and storage space differently.

• Baked Lightmaps: While they save GPU processing power, baked lightmaps require disk space and VRAM. High-resolution lightmap textures can significantly increase your game’s install size and consume valuable texture memory, which can be a bottleneck on lower-end devices.
• Real-Time Global Illumination: Real-time GI relies on algorithms and compute shaders rather than stored textures. This drastically reduces the game’s overall storage footprint and frees up VRAM, shifting the burden entirely onto the GPU’s processing cycles.

Development Workflow and Iteration Speed

The choice of lighting also shapes the daily production pipeline of your development team.

• Baking Pipelines: Baking lightmaps is a time-consuming process. Any change to a level’s geometry or light placement requires “re-baking,” which can take anywhere from a few minutes to several hours depending on scene complexity. This can slow down level designers and environment artists.
• Real-Time Pipelines: Real-time GI provides instant feedback. Artists can move lights, change colors, and adjust geometry, seeing the final results immediately in the viewport. This dramatically speeds up iteration times and allows for faster level design adjustments.