| 405 |
|
.BI -ab \ N |
| 406 |
|
Set the number of ambient bounces to |
| 407 |
|
.I N. |
| 408 |
< |
This is the maximum number of diffuse bounces |
| 409 |
< |
computed by the indirect calculation. |
| 410 |
< |
A value of zero implies no indirect calculation. |
| 408 |
> |
This is the maximum number of diffuse bounces computed by the indirect |
| 409 |
> |
calculation. A value of zero implies no indirect calculation. |
| 410 |
> |
.IP |
| 411 |
> |
This value defaults to 1 in photon mapping mode (see |
| 412 |
> |
.I -ap |
| 413 |
> |
below), implying that global photon irradiance is always computed via |
| 414 |
> |
.I one |
| 415 |
> |
ambient bounce; this behaviour applies to any positive number of ambient |
| 416 |
> |
bounces, regardless of the actual value specified. A negative value enables |
| 417 |
> |
a preview mode that directly visualises the irradiance from the global |
| 418 |
> |
photon map without any ambient bounces. |
| 419 |
|
.TP |
| 420 |
|
.BI -ar \ res |
| 421 |
|
Set the ambient resolution to |
| 524 |
|
except read modifiers to be included from |
| 525 |
|
.I file. |
| 526 |
|
.TP |
| 527 |
+ |
.BI -ap " file [bwidth1 [bwidth2]]" |
| 528 |
+ |
Enable photon mapping mode. Loads a photon map generated with |
| 529 |
+ |
.I mkpmap(1) |
| 530 |
+ |
from |
| 531 |
+ |
.I file, |
| 532 |
+ |
and evaluates the indirect irradiance depending on the photon type |
| 533 |
+ |
(automagically detected) using density estimates with a bandwidth of |
| 534 |
+ |
.I bwidth1 |
| 535 |
+ |
photons, or the default bandwidth if none is specified (a warning will be |
| 536 |
+ |
issued in this case). |
| 537 |
+ |
.IP |
| 538 |
+ |
Global photon irradiance is evaluated as part of the ambient calculation (see |
| 539 |
+ |
.I \-ab |
| 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. Contribution photons are treated as |
| 544 |
+ |
global photons by |
| 545 |
+ |
.I rpict. |
| 546 |
+ |
.IP |
| 547 |
+ |
Additionally specifying |
| 548 |
+ |
.I bwidth2 |
| 549 |
+ |
enables bias compensation for the density estimates with a |
| 550 |
+ |
minimum and maximum bandwidth of |
| 551 |
+ |
.I bwidth1 |
| 552 |
+ |
and |
| 553 |
+ |
.I bwidth2, |
| 554 |
+ |
respectively. |
| 555 |
+ |
.IP |
| 556 |
+ |
Global photon irradiance may be optionally precomputed by |
| 557 |
+ |
.I mkpmap(1), |
| 558 |
+ |
in which case the bandwidth, if specified, is ignored, as the nearest photon |
| 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. |
| 563 |
+ |
.TP |
| 564 |
+ |
.BI -am " frac" |
| 565 |
+ |
Maximum search radius for photon map lookups. Without this option, an |
| 566 |
+ |
initial maximum search radius is estimated for each photon map from the |
| 567 |
+ |
average photon distance to the distribution's centre of gravity. It is then |
| 568 |
+ |
adapted to the photon density in subsequent lookups. This option imposes a |
| 569 |
+ |
global fixed maximum search radius for |
| 570 |
+ |
.I all |
| 571 |
+ |
photon maps, thus defeating the automatic adaptation. It is useful when |
| 572 |
+ |
multiple warnings about short photon lookups are issued. Note that this |
| 573 |
+ |
option does not conflict with the bandwidth specified with the |
| 574 |
+ |
.I \-ap |
| 575 |
+ |
option; the number of photons found will not exceed the latter, but may be |
| 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, |
| 609 |
|
in units of 1/distance (distance in world coordinates). |
| 653 |
|
.BR \-u |
| 654 |
|
Boolean switch to control uncorrelated random sampling. |
| 655 |
|
When "off", a low-discrepancy sequence is used, which reduces |
| 656 |
< |
variance but can result in a brushed appearance in specular highlights. |
| 656 |
> |
variance but can result in a dithered appearance in specular highlights. |
| 657 |
|
When "on", pure Monte Carlo sampling is used in all calculations. |
| 658 |
|
.TP |
| 659 |
|
.BI -lr \ N |
| 666 |
|
termination, and the |
| 667 |
|
.I -lw |
| 668 |
|
setting (below) must be positive. |
| 669 |
< |
If N is a negative integer, then this sets the upper limit |
| 670 |
< |
of reflections past which Russian roulette will be used. |
| 669 |
> |
If N is a negative integer, then this limits the maximum |
| 670 |
> |
number of reflections even with Russian roulette. |
| 671 |
|
In scenes with dielectrics and total internal reflection, |
| 672 |
|
a setting of 0 (no limit) may cause a stack overflow. |
| 673 |
|
.TP |
| 887 |
|
rpict \-vp 10 5 3 \-vd 1 \-.5 0 scene.oct > scene.hdr |
| 888 |
|
.PP |
| 889 |
|
rpict \-S 1 \-o frame%02d.hdr scene.oct < keyframes.vf |
| 890 |
+ |
.PP |
| 891 |
+ |
To render ambient illuminance in photon mapping mode from a global photon |
| 892 |
+ |
map global.pm via one ambient bounce, and from a caustic photon map |
| 893 |
+ |
caustic.pm: |
| 894 |
+ |
.IP "" .2i |
| 895 |
+ |
rpict -ab 1 -ap global.pm 50 -ap caustic.pm 50 -vf scene.vf scene.oct > |
| 896 |
+ |
scene.hdr |
| 897 |
|
.SH ENVIRONMENT |
| 898 |
|
RAYPATH the directories to check for auxiliary files. |
| 899 |
|
.SH FILES |
| 913 |
|
.SH AUTHOR |
| 914 |
|
Greg Ward |
| 915 |
|
.SH "SEE ALSO" |
| 916 |
< |
getinfo(1), lookamb(1), oconv(1), pdfblur(1), pfilt(1), pinterp(1), pmblur(1), |
| 917 |
< |
printf(3), ra_rgbe(1), rad(1), rtrace(1), rvu(1) |
| 916 |
> |
getinfo(1), lookamb(1), mkpmap(1), oconv(1), pdfblur(1), pfilt(1), |
| 917 |
> |
pinterp(1), pmblur(1), printf(3), ra_rgbe(1), rad(1), rpiece(1), rtpict(1), rtrace(1), rvu(1) |
