Although managed by the list of geometry objects, objects of this type are not really geometric objects - they do not have geometric dimensions. Instead they count how many rays are absorbed by one of the materials. The material is assigned by drag&drop from the list of materials.

After the ray-tracing the absorption spectrum is computed by normalizing the absorbed rays to the number of emitted rays for each spectral position.

Please note that 'Absorbing material' objects count only those absorption events which occur inside a macroscopic volume. Absorption inside thin films of interfaces is not taken into account.

Objects of this type have been introduced to SPRAY in order to be able to 'record' absorption spectra of silicon wafers with textured surface.