Area Lights

Area Lights can be thought of as similar to a photographer’s softbox. In Unity they are defined as rectangles from which light is emitted in all directions, from one side only - the object’s +Z direction. Presently only available in Baked GI, these Area Lights illuminate uniformly across their surface area. There is no manual control for the range of an Area Light, however intensity will diminish at inverse square of the distance as it travels away from the source.

Light is emitted across the surface of an Area Light producing a diffuse light with soft shadowing.

Area Lights are useful in situations where you wish to create soft lighting effects. As light is emitted in all directions across the surface of the light, the rays produced travel in many directions - creating a diffuse lighting effect across a subject. A common use for this might be a ceiling striplight or a backlit panel.

In order to achieve this, we must fire a number of rays from each lightmap texel in the world, back towards the light in order to determine whether the light can be seen. This means that Area Lights can be quite computationally expensive and can increase bake times. However, used well, they can add a great depth of realism to your scene lighting and this extra precomputation may be justified. Note that as they are baked only, gameplay performance is not affected.