A solid cone zone: apex at (x, y, z), opening along +Y, widening to radius
over height — cones of cold, sprays, fountains, upward breath. A 3D volume,
so it works as a CrossZone boundary via _dead (a particle outside the cone
dies). Reflection (_bound/_cross) is not supported in v1. Axis-aligned to
+Y; arbitrary direction (e.g. horizontal dragon-breath) is a follow-up.
A solid cone zone: apex at (x, y, z), opening along +Y, widening to
radiusoverheight— cones of cold, sprays, fountains, upward breath. A 3D volume, so it works as aCrossZoneboundary via_dead(a particle outside the cone dies). Reflection (_bound/_cross) is not supported in v1. Axis-aligned to +Y; arbitrary direction (e.g. horizontal dragon-breath) is a follow-up.