LightProbe
LightProbe
Description
A marker component for a light probe, which is a cuboid region that provides global illumination to all fragments inside it.
Note that a light probe will have no effect unless the entity contains some kind of illumination, which can either be an [
EnvironmentMapLight] or an [IrradianceVolume].The light probe range is conceptually a unit cube (1×1×1) centered on the origin. The [
Transform] applied to this entity can scale, rotate, or translate that cube so that it contains all fragments that should take this light probe into account.When multiple sources of indirect illumination can be applied to a fragment, the highest-quality one is chosen. Diffuse and specular illumination are considered separately, so, for example, Bevy may decide to sample the diffuse illumination from an irradiance volume and the specular illumination from a reflection probe. From highest priority to lowest priority, the ranking is as follows:
Rank Diffuse Specular 1 Lightmap Lightmap 2 Irradiance volume Reflection probe 3 Reflection probe View environment map 4 View environment map Note that ambient light is always added to the diffuse component and does not participate in the ranking. That is, ambient light is applied in addition to, not instead of, the light sources above.
A terminology note: Unfortunately, there is little agreement across game and graphics engines as to what to call the various techniques that Bevy groups under the term light probe. In Bevy, a light probe is the generic term that encompasses both reflection probes and irradiance volumes. In object-oriented terms, light probe is the superclass, and reflection probe and irradiance volume are subclasses. In other engines, you may see the term light probe refer to an irradiance volume with a single voxel, or perhaps some other technique, while in Bevy light probe refers not to a specific technique but rather to a class of techniques. Developers familiar with other engines should be aware of this terminology difference.