Unformatted text preview: R incident
Iref lected R I Iincident
where RR isR is the (viewpoint dependent) reﬂectance
where is the (viewpoint dependent) reﬂectance function.
• where the (viewpoint dependent) reﬂectance function. function. !
!
Graphics Lecture 13: Slide 8!
. 4 / 29 .
4 / 29 Radiosity Radiosity"
Radiosity is deﬁned as the energy per unit area leaving a surface. • Radiosity is deﬁned as the energy per unit area leaving a
It is surface. of
the sum !
I the emitted energy
• It is the sum of! per unit area (if any)
I thethe emittedenergy. per unit area (if any) !
– reﬂected energy
– the reﬂected energy.! For For a small of the of the surface (patch) dA the emitted
• a small area area surface (patch) dA (where (where the
energy can be regarded as be regarded have:
emitted energy can constant) we as constant) we have:!
BdA = E dA + R I
Notice that that we treat light sources as distributed
• Notice we now now treat light sources as distributed ! Graphics Lecture 13: Slide 9! . 5 / 29 Divide the scene into patches i = 1, . . . , n Radiosity" For the ith patch, let:
• = total energy leaving
I BiDivide the scene into patches i = 1, ..., n
• = the energy emitted
I EiFortotalith patch, let:! by patch itself – Bi = total energy leaving the patch!
Ri = reﬂectance value
– Ei = total energy emitted by patch itself!
I Ii = incident light energy arriving at the patch
– Ri = reﬂectance value!
– Ii = incident light energy arriving at the patch!
I With this notation, the equation can be rewritten
With •this notation, the above above equation can be rewritten! Bi = Ei + Ri Ii (1) . Graphics Lecture 13: Slide 10! 6 / 29 Collecting energy
Collecting energy "
We can estimate incident energy for patch i as:
We can estimate the the incident energy for patch i as: !
Ii = n
X Bj Fij j =1 where the sum is taken all surface patches of the of the
Where the sum is taken overover all surface patches scene
scene !
The Bj ’s’s in the sum repre...
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 Spring '14
 Energy, Light, form factor, Rendering

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