Light Modes

There are three Light ModesA Light property that defines the use of the Light. Can be set to Realtime, Baked and Mixed. More info
See in Glossary available in the Light Inspector:

• Baked: The direct and indirect lighting from these lights is baked into lightmapsA pre-rendered texture that contains the effects of light sources on static objects in the scene. Lightmaps are overlaid on top of scene geometry to create the effect of lighting. More info
  See in Glossary, which can be a time-consuming process. There is no runtime cost to process these lights, however applying the resulting lightmaps to the sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
  See in Glossary does have a minor cost.
• Realtime: The direct lighting and shadows from these lights are real-time and therefore not baked into lightmaps. Their runtime cost can be high, depending on the complexity of the scene, the number of shadow casting lights, the number of overlapping lights, etc. Furthermore, if you enable EnlightenA lighting system by Geomerics used in Unity for Enlighten Realtime Global Illumination. More info
  See in Glossary Realtime Global IlluminationA group of techniques that model both direct and indirect lighting to provide realistic lighting results.
  See in Glossary, further performance costs will be incurred to update the indirect lighting at runtime.
• Mixed: This is a hybrid mode that offers a mix of baked and real-time features, such as baked indirect lighting and real-time direct lighting. The behavior of all Mixed lights in your Scene and their performance impact depends on the Lighting Mode for that Scene.

It is important to note that the mode of a light is only relevant if the Baked Global Illumination system is enabled. If you do not use any global illumination system or only use Enlighten Realtime Global Illumination system, then all Baked and Mixed lights will behave as though their Mode property was set to Realtime.

Realtime

These are also known as Realtime Lights.

Unity performs the lighting calculations for Realtime Lights at runtime, once per frame. You can change the properties of Realtime Lights at runtime to create effects such as flickering light bulbs, or a torch being carried through a dark room.

Realtime Lights are useful for lighting and casting shadows on characters or moveable geometry.

Realtime Light behavior

• Realtime Lights cast shadows up to the Shadow Distance.
• By default, Realtime Lights contribute only realtime direct lighting to a Scene. If you’re using the Built-in Render PipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
  See in Glossary and you enable Enlighten Realtime Global Illumination in your Project, Realtime Lights also contribute realtime indirect lighting to your Scene.

Limitations of Realtime Lights

• Performing runtime calculations for Realtime Lights might be costly, especially in complex scenes or on low-end hardware.
• Because Realtime Lights only contribute direct lighting to the Scene by default, shadows appear completely black and there aren’t any indirect lighting effects, such as color bounce. This might cause unrealistic lighting in the Scene.

Mixed

These are also known as Mixed Lights.

Mixed Lights combine elements of both real-time and baked lighting. You can use Mixed Lights to combine dynamic shadows with baked lighting from the same light source, or when you want a light to contribute direct real-time lighting and baked indirect lighting.

To use Mixed Lights, you must first understand the benefits and limitations of Realtime LightsLight components whose Mode property is set to Realtime. Unity calculates and updates the lighting of Realtime Lights every frame at runtime. No Realtime Lights are precomputed. More info
See in Glossary and Baked LightsLight components whose Mode property is set to Baked. Unity pre-calculates the illumination from Baked Lights before runtime, and does not include them in any runtime lighting calculations. More info
See in Glossary.

Mixed Light behavior

• The behavior of all Mixed Lights in a Scene depends on the Lighting Mode setting in the Lighting window. The different Lighting Modes have very different performance characteristics, and different levels of visual fidelity. For more information, see Lighting Modes.
• You can change properties of Mixed Lights at runtime. This updates their real-time lighting but not their baked lighting. When doing this, take care to avoid unwanted visual effects.

Limitations of Mixed Lights

• The performance cost of Mixed Lights differs considerably, depending on the Lighting Mode. However, because Mixed Lights always combine at least some real-time and some baked lighting, Mixed Lights always involve more runtime calculations than fully baked lighting, and higher memory usage than fully real-time lighting.

Note that if you disable Baked Global Illumination in your Scene, Unity forces Mixed Lights to behave as though you set their Mode to Realtime. When this happens, Unity displays a warning on the Light component InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary.

Baked

These are also known as Baked Lights.

Unity performs the calculations for Baked Lights in the Unity Editor, and saves the results to disk as lighting data. This process is called baking. At runtime, Unity loads the baked lighting data, and uses it to light the Scene. Because the complex calculations are performed in advance, Baked Lights reduce shading cost at runtime, and reduce the rendering cost of shadows.

Baked Lights are useful for lighting things that won’t change at runtime, such as scenery.

Baked Light behavior

• Unity bakes both direct lighting and indirect lighting from Baked Lights into lightmaps. For more information on using lightmaps, see lightmapping.
• Unity bakes both direct and indirect lighting from Baked Lights into Light Probes. For more information on using Light Probes, see Light ProbesLight probes store information about how light passes through space in your scene. A collection of light probes arranged within a given space can improve lighting on moving objects and static LOD scenery within that space. More info
  See in Glossary.

Limitations of Baked Lights

• You cannot change the properties of Baked Lights at runtime.
• Baked Lights do not contribute to specular lighting.
• Dynamic GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
  See in Glossary do not receive light or shadow from Baked Lights.

Note that if you disable Baked Global Illumination in your Scene, Unity forces Baked Lights to behave as though you set their Mode to Realtime. When this happens, Unity displays a warning on the Light component Inspector.