| Constraints on the BRDF |
|
|
|
|
|
|
|
|
|
|
|
| Energy
conservation |
||||||||||
| • | Quantity of
outgoing light ≤ quantity of incident light |
|||||||||
| – | integral of BRDF ≤
1 |
|||||||||
| Helmholtz
reciprocity |
||||||||||
| • | reversing the
path of light produces the same reflectance |
|||||||||
| = |