Radiosity
Spring 1999
(1984 Goral, et. al, at Cornell)
Cornell Box Radiosity simulation
Radiosity Equations
This gives us:
OR
Form Factors:
So
Which can be rewritten as
Or the radiosity matrix
where and
are wavelength dependent.
only for lights.
for convex surface.
Some Important Points to Note:
Radiosity Stages
Computational Bottleneck: form factor calculations, O(n^{2})
Discretization resolution determines accuracy of solution
To increase accuracy, use
Caculate Element-Patch form factors
where
F.F. from patch i to patch j
F.F. from element q of patch i to patch j
area of element q of patch i
R = # of elements in patch i.
-- now have form factors
Calculating element radiosities
for an element, only look at other patches, not elements.
Resulting operations needed:
Progressive Refinement
For all j:
where .
Shooting Algorithm
Repeat
For each Patch i
for first iteration calculate F.F. .
For each Patch j ()
{
}
Until convergence
Improvements:
Form Factor Issues
Form Factor = fraction of unit circle taken up by projection.