shadowCasterChannelMask property
The light channels whose nodes render into this spot's shadow map, an
8-bit mask (default 0xFF, every channel). A node casts only when
shadowCasterChannelMask & node.lightChannelMask is nonzero.
Deliberately independent of channelMask: a node excluded from the lighting still casts unless this mask drops it too, so hiding geometry from a spot takes clearing it here as well.
Implementation
int shadowCasterChannelMask;