| 89 |
|
.IP |
| 90 |
|
w weight |
| 91 |
|
.IP |
| 92 |
< |
W contribution |
| 92 |
> |
W color coefficient |
| 93 |
|
.IP |
| 94 |
|
l effective length of ray |
| 95 |
|
.IP |
| 178 |
|
This option is especially useful in |
| 179 |
|
conjunction with ximage(1) for computing illuminance at scene points. |
| 180 |
|
.TP |
| 181 |
+ |
.BR \-R |
| 182 |
+ |
Boolean switch to control random sampling. |
| 183 |
+ |
When "off", a low-discrepancy sequence is used, which reduces |
| 184 |
+ |
variance but can result in a brushed appearance in specular highlights. |
| 185 |
+ |
When "on", pure Monte Carlo sampling is used in all calculations. |
| 186 |
+ |
.TP |
| 187 |
|
.BR \-I |
| 188 |
|
Boolean switch to compute irradiance rather than radiance, |
| 189 |
|
with the input origin and direction interpreted instead |
| 524 |
|
.BI -lr \ N |
| 525 |
|
Limit reflections to a maximum of |
| 526 |
|
.I N. |
| 527 |
+ |
If |
| 528 |
+ |
.I N |
| 529 |
+ |
is zero or negative, then Russian roulette is used for ray |
| 530 |
+ |
termination, and the |
| 531 |
+ |
.I -lw |
| 532 |
+ |
setting (below) must be positive. |
| 533 |
+ |
If N is a negative integer, then this sets the upper limit |
| 534 |
+ |
of reflections past which Russian roulette will not be used. |
| 535 |
+ |
In scenes with dielectrics and total internal reflection, |
| 536 |
+ |
a setting of 0 (no limit) may cause a stack overflow. |
| 537 |
|
.TP |
| 538 |
|
.BI -lw \ frac |
| 539 |
|
Limit the weight of each ray to a minimum of |
| 540 |
|
.I frac. |
| 541 |
< |
During ray-tracing, a record is kept of the final contribution |
| 542 |
< |
a ray would have to the image. |
| 543 |
< |
If it is less then the specified minimum, the ray is not traced. |
| 541 |
> |
During ray-tracing, a record is kept of the estimated contribution |
| 542 |
> |
(weight) a ray would have in the image. |
| 543 |
> |
If this weight is less than the specified minimum and the |
| 544 |
> |
.I -lr |
| 545 |
> |
setting (above) is positive, the ray is not traced. |
| 546 |
> |
Otherwise, Russian roulette is used to |
| 547 |
> |
continue rays with a probability equal to the ray weight |
| 548 |
> |
divided by the given |
| 549 |
> |
.I frac. |
| 550 |
|
.TP |
| 551 |
|
.BR -ld |
| 552 |
|
Boolean switch to limit ray distance. |
