channelMask property
The light channels this spot illuminates, an 8-bit mask (default 0xFF,
every channel). A node receives this light only when
channelMask & node.lightChannelMask is nonzero, so a zero mask on
either side never intersects. Channels do not affect image-based
(environment) lighting, which every node receives.
Gates the lighting only. Every caster still renders into this spot's shadow map; only DirectionalLight.shadowCasterChannelMask filters casters.
Implementation
int channelMask;