| 540 |
|
above), caustic photon irradiance is evaluated at primary rays, and |
| 541 |
|
indirect inscattering in |
| 542 |
|
.I mist |
| 543 |
< |
is accounted for by volume photons. |
| 543 |
> |
is accounted for by volume photons. Contribution photons are treated as |
| 544 |
> |
global photons by |
| 545 |
> |
.I rpict. |
| 546 |
|
.IP |
| 547 |
|
Additionally specifying |
| 548 |
|
.I bwidth2 |
| 559 |
|
is invariably looked up. |
| 560 |
|
.IP |
| 561 |
|
Using direct photons replaces the direct calculation with density estimates |
| 562 |
< |
for debugging and validation of photon emission. |
| 562 |
> |
for debugging and validation of photon emission. |
| 563 |
|
.TP |
| 564 |
|
.BI -am " frac" |
| 565 |
|
Maximum search radius for photon map lookups. Without this option, an |
| 576 |
|
lower if the maximum search radius contains fewer photons, thus resulting in |
| 577 |
|
short lookups. Setting this radius too large, on the other hand, may |
| 578 |
|
degrade performance. |
| 579 |
+ |
.TP |
| 580 |
+ |
.BI -ac " pagesize" |
| 581 |
+ |
Set the photon cache page size when using out-of-core photon mapping. The |
| 582 |
+ |
photon cache reduces disk I/O incurred by on-demand loading (paging) of |
| 583 |
+ |
photons, and thus increases performance. This |
| 584 |
+ |
is expressed as a (float) multiple of the density estimate bandwidth |
| 585 |
+ |
specified with |
| 586 |
+ |
.I \-ap |
| 587 |
+ |
under the assumption that photon lookups are local to a cache page. Cache |
| 588 |
+ |
performance is sensitive to this parameter: larger pagesizes will reduce the |
| 589 |
+ |
paging frequency at the expense of higher latency when paging does occur. |
| 590 |
+ |
Sensible values are in the range 4 (default) to 16. |
| 591 |
+ |
.TP |
| 592 |
+ |
.BI -aC " cachesize" |
| 593 |
+ |
Set the total number of photons cached when using out-of-core photon |
| 594 |
+ |
mapping, taking into account the pagesize specified by |
| 595 |
+ |
.I \-ac. |
| 596 |
+ |
Note that this is approximate as the number of cache pages is rounded to |
| 597 |
+ |
the nearest prime. This allows adapting the cache to the available physical |
| 598 |
+ |
memory. In conjunction with the |
| 599 |
+ |
.I \-n |
| 600 |
+ |
option, this is the cache size |
| 601 |
+ |
.I per parallel process. |
| 602 |
+ |
Cache performance is less sensitive to this parameter, |
| 603 |
+ |
and reasonable performance can obtained with as few as 10k photons. The |
| 604 |
+ |
default is 1M. This option recognises multiplier suffixes (k = 1e3, M = |
| 605 |
+ |
1e6), both in upper and lower case. |
| 606 |
|
.TP |
| 607 |
|
.BI -me " rext gext bext" |
| 608 |
|
Set the global medium extinction coefficient to the indicated color, |
