Geometry Transformation
The objective is, for every reflector of the scene, to find a method to compute a virtual object for every other object reflected in it. This virtual reflected object is then rendered and blended with the scene.
Ray tracing in the sampled geometry
The objective is to compute reflections, refractions and caustics based on an image-based representation of the environment. This representation can be considered a sampled version of the scene, enabling searches to trace rays.