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|Title: ||Real time progressive radiosity in dynamic environment with multiresolution|
|Authors: ||Chen, Frank Jun|
|Department: ||Department of Computer Science|
|Issue Date: ||2004|
|Supervisor: ||Dr. Lau Rynson. First Reader: Dr. Wong Hau San. Second Reader: Dr. Ip Horace|
|Abstract: ||In this project, a new method is presented to shorten calculation time of progressive
radiosity [Cohen88] in dynamic environments. The dynamic object has been simplified into the
one with lower resolution by implementing edge contraction algorithm [Hoppe96] [Garland97].
One radiosity cycle contains two significant steps: one is calculating radiosity distribution in the
scene and the other one is rendering the scene. The dynamic object in the lower resolution form
is used to calculate radiosity and the one in the higher resolution form is used to render the
scene. Before rendering, the radiosity in the simple model is transferred to the complex one
through vertex hierarchy. The algorithm also maintains the shadow of dynamic object very well
by implementing Shadow Form Factor Algorithm (SFFL) [Schoffel95].
The essential aim of this project is to achieve real time progressive radiosity. There are two
difficulties to achieve this aim:
?? When the number of patches in the scene increases significantly, the calculation time
will become overwhelming.
?? In order to deal with dynamic environments, the radiosities distributed in each cycle
must be redistributed. So if the number of iterations increases, the calculation time will
become overwhelming as well.
In order to solve the first problem, Edge Contraction algorithm is implemented to decrease
the number of patches in the scene. However, new criterion of vertex pair selection is defined to
suit this project. A new algorithm is also proposed to transfer radiosity from the model with
lower resolution to the one with higher resolution.
As described above, SFFL algorithm is implemented in this project to deal with
shadows. In each cycle, SFFL will add a certain energy to old shadow and remove a certain
energy from new shadow and update energy of patches in dynamic object. When the number of
iterations increases, the calculation time of SFFL becomes siginificantly unacceptable. In order
to solve this problem, improvement is made to this algorithm. Instead of recalculating radiosity
distributions in each cycle, the unshot radiosity in iterations with the same shooting patch are
summed up and redistributed once to the environment. In this way, when the number of
iterations increases, the calculation time will not increase obviously.
Besides dealing with shadows, calculating form factor in each cycle also contributes a lot
of calculation time. Improvement is also made to progressive radiosity. In some cycle, if the
shooting patch is the first time to be an emitter, store the form factor values. In some other cycle,
if the patch becomes an emitter again, use the form factor stored in the previous cycle directly to
calculate received energy from the shooting patch. In this way, form factor is only calculated
In this report, a detailed survey of previous works on radiosity, multi-resolution algorithms
and algorithms integrating both is included. There is also a detailed discussion on my proposed
algorithm. Finally, results and future work are also discussed.|
|Appears in Collections:||Computer Science - Undergraduate Final Year Projects|
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