| 26 |
|
matrix is the right way around for the 3-phase method already. |
| 27 |
|
Second, WINDOW 6 generally produces correct data for "Transmission |
| 28 |
|
Front," but in some cases just has dummy values as a placeholder |
| 29 |
< |
for the "Transmission Back" matrix. (Someone correct me on this |
| 30 |
< |
if I am mistaken, but that's what I understood.) |
| 29 |
> |
for the "Transmission Back" matrix. |
| 30 |
|
|
| 31 |
+ |
For the tensor tree representation, reciprocity can be used to |
| 32 |
+ |
derive all needed information for 4-D distributions, so only one |
| 33 |
+ |
tree is stored to save file space and memory. However, isotropic |
| 34 |
+ |
(3-D) data does not use reciprocity for sampling, even though it |
| 35 |
+ |
can use it to answer BTDF queries, because it would require too |
| 36 |
+ |
much work to build up a 4-D structure then derive the 3-D information |
| 37 |
+ |
from it. So, this is a caveat, and genBSDF will create reverse-flow |
| 38 |
+ |
isotropic BTDF data if run with +forward and +backward in this case. |
| 39 |
+ |
|
| 40 |
|
The situation is a bit simpler in the case of reflection, since one |
| 41 |
< |
cannot construct the front reflection matrix from the rear or vice |
| 41 |
> |
cannot construct the front reflection data from the rear or vice |
| 42 |
|
versa. If one of the reflectance matrices is missing during |
| 43 |
|
rendering, then the surface gets no reflected contributions from |
| 44 |
|
that side. The 3-phase method does not make use of reflectance, |
