In this talk I introduce the formulation for ray-tracing of particles in the Kerr spacetime. Merging this formulation with calculations of radiative transfer in full general relativity several situations including geometrically thin (optically) accretion disks through to geometrically thick (optically thin) accretion tori with different thermodynamic properties are investigated. The electromagnetic emission from these systems is calculated and the physical and observational consequences are discussed. The remainder of the talk concerns the formulation of a proper treatment of electron scattering in full general relativity, as well as how such a formulation may be implemented in future radiation transport codes.