Arbitrary illumination fields

[carterbox]

Currently, XDesign only supports illuminations based on probes represented by parallel lines. However this means that cone beam or other focused beam systems cannot be simulated. Instead I propose that illuminations are represented as polygonal meshes where each element of the mesh represents the photons collected by one detector element. In this way, the modeling of a cone beam could be a mesh of triangles which all share a single point.