Lighting is one of the most essential elements in any 3D scene, shaping the perception of depth, mood, and realism. When working with real-time rendering, particularly in game engines or interactive applications, the challenge is to balance visual quality and performance. Baked lighting is a technique used to pre-compute light data and store it as textures or maps to be used in real-time, greatly improving rendering efficiency while maintaining high-quality lighting effects. In this guide, we’ll explore everything you need to know about baked lighting, from the fundamentals to best practices in popular 3D engines like Unity, Unreal Engine, and Blender.
Baked lighting refers to pre-computing lighting effects and storing them as static data. These pre-calculated lighting details include direct and indirect light, shadows, and global illumination, which are then stored in lightmaps, textures that are applied to 3D models during the rendering process. The key benefit of baked lighting is its ability to simulate complex lighting conditions, such as soft shadows and global illumination, without requiring the computational power of real-time dynamic lighting.
In real-time rendering, lighting can be classified as static, dynamic, or a combination of both (mixed). Understanding the differences between these types will help you decide which approach best suits your scene and performance requirements.
Static lighting refers to lighting that is baked into the scene and remains constant. This is ideal for environments that do not change or require interactivity, such as architectural visualizations. Static lights are calculated once and do not change during gameplay or simulation.
Dynamic lighting is calculated in real time, allowing for objects to cast shadows, light to move, and environmental factors to affect the scene’s lighting. This is essential for elements that need to interact dynamically with the environment, such as moving characters or changing weather conditions.
Mixed lighting is a combination of static and dynamic lighting. In this approach, static lighting (like ambient light or distant sunlight) is baked, while dynamic lighting (such as spotlights or player-activated lights) is rendered in real-time. This approach offers a balance between performance and flexibility.
The process of baking lighting varies slightly between 3D software and game engines, but the core principles are the same. Below, we’ll break down the basic steps for setting up baked lighting in Unity, Unreal Engine, and Blender.
Before you can bake lighting into your scene, it’s important to properly prepare your assets. This includes ensuring proper UV unwrapping, setting an appropriate lightmap resolution, and maintaining consistent texel density.
UV unwrapping is the process of flattening a 3D model's surface into a 2D layout so that textures can be applied. For lightmaps, it’s crucial that UVs do not overlap and are evenly spaced to prevent lighting artifacts like seams or uneven shadows.
The resolution of lightmaps directly impacts the quality and detail of the baked lighting. Higher resolutions provide better quality but at the cost of increased memory usage. The key is finding a balance between quality and performance. Typically, lightmaps are generated at 512x512, 1024x1024, or 2048x2048 resolutions, depending on the size of the object and the camera’s distance from it.
Texel density refers to the number of texture pixels (texels) per unit of 3D surface area. Ensuring consistent texel density across all objects in a scene helps maintain uniform texture quality and prevents texture stretching or blurring. Tools in Blender can help automate texel density adjustments for better efficiency.
Baked lighting is not just about direct light; it also involves simulating global illumination (GI) and baking shadows to enhance realism. Global illumination simulates how light bounces off surfaces and affects other objects in the scene. Baking GI and shadows can drastically improve both the look and performance of a scene by eliminating the need for real-time calculations.
Shadow baking stores pre-calculated shadow data into the lightmaps, giving static objects realistic shadows without the computational overhead of dynamic shadow calculations. Be sure to consider factors like shadow softness and resolution to ensure the shadows blend naturally with the environment.
Once lighting is baked, it’s essential to optimize the lightmaps to reduce memory usage and ensure quick load times. Several techniques can be employed:
Lightmaps can be compressed to reduce their size without losing significant visual quality. Most 3D software and engines support lightmap compression, which is especially useful for mobile games or applications with tight memory constraints.
Atlasing involves packing multiple lightmaps into a single texture to reduce the number of textures the engine needs to handle. This can save memory and improve performance, especially in large scenes.
Optimizing the memory footprint of lightmaps is crucial for maintaining performance. Adjusting lightmap resolution, using compression, and properly packing UVs can significantly reduce the memory footprint of lightmaps, especially in larger scenes.
When baking lighting, common artifacts can arise that affect the quality of the final render. These include seams, light bleeding, and splotches, which can make the lighting appear unnatural or unrealistic.
Seams can occur when UV islands are not properly aligned or when textures don’t seamlessly fit together. This can be fixed by ensuring proper UV unwrapping and using tools like the Texel Density Checker to ensure consistency.
Light bleeding happens when light leaks into areas it shouldn’t, often due to poorly sealed seams or insufficient lightmap resolution. To prevent light bleeding, increase the resolution of your lightmaps and ensure proper padding between UV islands.
Splotches can occur when the baking process fails to interpolate light data correctly. This can be mitigated by adjusting the bake settings, increasing the lightmap resolution, and ensuring your lighting setup is correct.
Baked lighting is a powerful tool in real-time rendering, offering an effective way to balance visual quality and performance. By understanding the fundamentals of baked lighting, choosing the right lighting approach for your scene, and optimizing your assets, you can achieve stunning results without sacrificing performance. Whether you’re working in Unity, Unreal Engine, or Blender, mastering the light-baking workflow will elevate your 3D rendering skills and create more immersive, realistic environments. Happy baking!
