Home computers cannot render photoreal lighting at 90 frames per second; so by ‘baking the lighting’, the computer calculates photo-realistic lighting only once, and then applies this lighting to all objects in the scene. It does this by converting the lighting data into ‘lightmap’ textures.
Pros and Cons of Baked Lighting:
Every light-baked 3D Model must have two UV Mapping Channels, so that both textures and lightmaps can be applied to them.
Baked lighting increases the application’s file size, and can require many hours of test-baking to get right due to errors in light baking caused by UV seam issues.
Architecture that is too elongated must also be separated into multiple 3D models in order to fit into the correct UV Map dimensions for light baking.
These extra tasks mean that a light baked scene can take up to 50% longer to create.
Baked lights also lack the ability to be moved in-game, but can be combined with dynamic lights if movable lighting is needed.
Most people agree that the extra financial cost it takes to complete these tasks are worth the photo-realistic quality, but if reducing monetary costs is a priority, then it may be better to use dynamic lighting and avoid light baking. The quality of dynamic lighting is not as good, and performance is slightly worse, but choosing dynamic lighting may save many hours of 3D modelling.
Almost all applications designed for VR use a combination of baked and dynamic lighting, as interactive architectural walkthroughs require movable components like doors and light switches. It is standard procedure to use light baking for everything that doesn’t move, and use dynamic lights for movable objects.
It is also possible to prepare your project with dynamic lighting to see how it appears before making the choice on whether or not to use baked lighting.