  We examine radiation and its effects on accretion disks orbiting
astrophysical black holes. These disks are thermally radiating and can be
geometrically and optically thin or thick. In this first paper of the series,
we discuss the physics and the formulation required for this study.
Subsequently, we construct and solve the relativistic radiative transfer
equation, or find suitable solutions where that is not possible. We continue by
presenting some of the accretion disks we considered for this work. We then
describe the families of codes developed in order to study particle
trajectories in strong gravity, calculate radiation forces exerted onto the
disk material, and generate observation pictures of black hole systems at
infinity. Furthermore, we also examine the veracity and accuracy of our work.
Finally, we investigate how we can further use our results to estimate the
black hole spin and the motion of disk material subjected to these radiation
forces.
