An emitter defines the light emission properties of a surface. It is assigned to a material
The generic emitter type is defined by a base emission spectrum, an angular distribution function and a position modulation function. The final radiance is the product of the three functions.
The planar IES emitter uses IES data and extracts the half-sphere equivalent radiance for a planar source. It is suited for IES sources which have no or little light emitted in the back direction.
The spherical IES emitter uses IES data and for any point on a sphere geometry, derives a planar source model, so that the full sphere has the same radiance distribution as the IES data. It is suited for any kind of IES source, and requires to be applied on a sphere geometry.