  In this paper we broadly consider techniques which utilize projections on
rays for data collection, with particular emphasis on optical techniques. We
formulate a variety of imaging techniques as either special cases or extensions
of tomographic reconstruction. We then consider how the techniques must be
extended to describe objects containing occlusion, as with a self-occluding
opaque object. We formulate the reconstruction problem as a regularized
nonlinear optimization problem to simultaneously solve for object brightness
and attenuation, where the attenuation can become infinite. We demonstrate
various simulated examples for imaging opaque objects, including sparse point
sources, a conventional multiview reconstruction technique, and a
super-resolving technique which exploits occlusion to resolve an image.
