The
Radiosity problem has been originally proposed as a finite element problem,
which is solved by tesseletating uniformly (in the logical space) the
input surfaces. Although, one can increase the accuracy of the solution by
subdiving surface more and more, still some problems exist that are very annoying
to the human eye. These problems are closely related to the uniform way of
subdivision, i.e. they are presented in the form of aliasing artifacts.
These are: (a) light leakage, (b) shadow leakage and (c) staircase effect.
Discontinuity meshing is a way of achieving high numerical and visual accuracy when performing radiosity computations and it was first proposed by Heckbert [1992] and Lischinski et al. [1992,1993]. Instead of subdiving surfaces in a uniform way, the whole environment is taken into account, in order to construct certain types of virtual discontinuity surfaces. The intersection of these virtual surfaces with the input surfaces will yield the discontinuity segments which are used to guide the subdivision process. In a polygonal environment, two different types of virtual discontinuity surfaces arise: (a) VE event (planar surface) which is formed by a vertex and an edge of the environment and (b) EEE event (quadric surface) which is formed by three edges of the environment. The former surfaces are easier to handle and fortunately, they correspond to most annoying artifacts (D0, D1 discontinuities). |
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