| 422 |
|
0 |
| 423 |
|
3 red green blue |
| 424 |
|
.DE |
| 425 |
+ |
While alternate materials that are reflective will appear as normal, |
| 426 |
+ |
indirect rays will use the mirror's reflectance rather than the |
| 427 |
+ |
alternate type. |
| 428 |
+ |
Transmitting materials are an exception, where both transmission and |
| 429 |
+ |
reflection will use the alternate type for all rays not specifically |
| 430 |
+ |
targeting virtual light sources. |
| 431 |
+ |
In this case, it is important that any reflections be purely specular |
| 432 |
+ |
(mirror-like) and equal to the mirror's reflectivity |
| 433 |
+ |
to maintain a valid result. |
| 434 |
+ |
A pure diffuse reflection may be added if desired. |
| 435 |
+ |
.PP |
| 436 |
+ |
The mirror material type reflects light sources only from the front side |
| 437 |
+ |
of a surface, regardless of any alternate material. |
| 438 |
+ |
If virtual source generation is desired on both sides, two coincident |
| 439 |
+ |
surfaces with opposite normal orientations may be employed to achieve |
| 440 |
+ |
this effect. |
| 441 |
+ |
The reflectance and alternate material type may be |
| 442 |
+ |
different for the overlapped surfaces, |
| 443 |
+ |
and the two sides will behave accordingly. |
| 444 |
|
.LP |
| 445 |
|
.UL Prism1 |
| 446 |
|
.PP |
