| 68 |
|
In the second invocation form, |
| 69 |
|
.I bsdf2ttree |
| 70 |
|
takes a functional specification of a BSDF. |
| 71 |
< |
The named function must accept 6 parameters corresponding to the |
| 71 |
> |
The named function should accept 6 parameters corresponding to the |
| 72 |
|
normalized incident and exiting vectors, respectively. |
| 73 |
|
By convention, these vectors point away from the surface, and a positive |
| 74 |
|
Z-component corresponds to the front side. |
| 75 |
|
The Y-component corresponds to the "up" orientation of the surface, |
| 76 |
|
as specified in the eventual scene description that references the XML |
| 77 |
|
output. |
| 78 |
+ |
If the function only takes 3 parameters, then the variables "Dx", "Dy", |
| 79 |
+ |
and "Dz" will be assigned to the reverse of the outgoing direction at |
| 80 |
+ |
each evaluation. |
| 81 |
+ |
(I.e., the vector will point into the surface and |
| 82 |
+ |
Dz will be negative on the front side.)\0 |
| 83 |
+ |
This simplifies conversion of functional BSDF specifications using the |
| 84 |
+ |
legacy material primitives "plasfunc", "metfunc", and "transfunc". |
| 85 |
|
.PP |
| 86 |
|
The function is defined by one or more |
| 87 |
|
.I \-e |
