| 401 |
|
.BI -ab \ N |
| 402 |
|
Set the number of ambient bounces to |
| 403 |
|
.I N. |
| 404 |
< |
This is the maximum number of diffuse bounces |
| 405 |
< |
computed by the indirect calculation. |
| 406 |
< |
A value of zero implies no indirect calculation. |
| 404 |
> |
This is the maximum number of diffuse bounces computed by the indirect |
| 405 |
> |
calculation. A value of zero implies no indirect calculation. |
| 406 |
> |
.IP |
| 407 |
> |
In photon mapping mode (see |
| 408 |
> |
.I -ap |
| 409 |
> |
below), a positive value implies that global photon irradiance is |
| 410 |
> |
always computed via |
| 411 |
> |
.I one |
| 412 |
> |
ambient bounce. A negative value enables a preview mode that directly |
| 413 |
> |
visualises the irradiance from the global photon map without any ambient |
| 414 |
> |
bounces. |
| 415 |
|
.TP |
| 416 |
|
.BI -ar \ res |
| 417 |
|
Set the ambient resolution to |
| 517 |
|
except read modifiers to be included from |
| 518 |
|
.I file. |
| 519 |
|
.TP |
| 520 |
+ |
.BI -ap " file [bwidth1 [bwidth2]]" |
| 521 |
+ |
Enable photon mapping mode. Loads a photon map generated with |
| 522 |
+ |
.I mkpmap(1) |
| 523 |
+ |
from |
| 524 |
+ |
.I file, |
| 525 |
+ |
and evaluates the indirect irradiance depending on the photon type |
| 526 |
+ |
(automagically detected) using density estimates with a bandwidth of |
| 527 |
+ |
.I bwidth1 |
| 528 |
+ |
photons, or the default bandwidth if none is specified (a warning will be |
| 529 |
+ |
issued in this case). |
| 530 |
+ |
.IP |
| 531 |
+ |
Global photon irradiance is evaluated as part of the ambient calculation (see |
| 532 |
+ |
.I \-ab |
| 533 |
+ |
above), caustic photon irradiance is evaluated at primary rays, and |
| 534 |
+ |
indirect inscattering in |
| 535 |
+ |
.I mist |
| 536 |
+ |
is accounted for by volume photons. |
| 537 |
+ |
.IP |
| 538 |
+ |
Additionally specifying |
| 539 |
+ |
.I bwidth2 |
| 540 |
+ |
enables bias compensation for the density estimates with a |
| 541 |
+ |
minimum and maximum bandwidth of |
| 542 |
+ |
.I bwidth1 |
| 543 |
+ |
and |
| 544 |
+ |
.I bwidth2, |
| 545 |
+ |
respectively. |
| 546 |
+ |
.IP |
| 547 |
+ |
Global photon irradiance may be optionally precomputed by |
| 548 |
+ |
.I mkpmap(1), |
| 549 |
+ |
in which case the bandwidth, if specified, is ignored, as the nearest photon |
| 550 |
+ |
is invariably looked up. |
| 551 |
+ |
.IP |
| 552 |
+ |
Using direct photons replaces the direct calculation with density estimates |
| 553 |
+ |
for debugging and validation of photon emission. |
| 554 |
+ |
.TP |
| 555 |
+ |
.BI -am " frac" |
| 556 |
+ |
Coefficient for maximum search radius for photon map lookups. The search |
| 557 |
+ |
radius is automatically determined based on the average photon distance to the |
| 558 |
+ |
distribution's centre of gravity, and scaled by this coefficient. Increase this |
| 559 |
+ |
value if multiple warnings about short photon lookups are issued. |
| 560 |
+ |
.TP |
| 561 |
|
.BI -me " rext gext bext" |
| 562 |
|
Set the global medium extinction coefficient to the indicated color, |
| 563 |
|
in units of 1/distance (distance in world coordinates). |
| 681 |
|
on most multiprocessing platforms, since the |
| 682 |
|
.I fork(2) |
| 683 |
|
system call will share memory on a copy-on-write basis. |
| 684 |
+ |
.SH NOTES |
| 685 |
+ |
Photons are generally surface bound (an exception are volume photons), thus |
| 686 |
+ |
the ambient irradiance in photon mapping mode will be biased at positions |
| 687 |
+ |
which do not lie on a surface. |
| 688 |
|
.SH EXAMPLES |
| 689 |
|
To compute radiance values for the rays listed in samples.inp: |
| 690 |
|
.IP "" .2i |
| 704 |
|
.IP "" .2i |
| 705 |
|
cnt 480 640 | rcalc \-e 'xr:640;yr:480' \-f unusual_view.cal | rtrace |
| 706 |
|
\-x 640 \-y 480 \-fac scene.oct > unusual.hdr |
| 707 |
+ |
.PP |
| 708 |
+ |
To compute ambient illuminance in photon mapping mode from a global photon |
| 709 |
+ |
map global.pm via one ambient bounce, and from a caustic photon map |
| 710 |
+ |
caustic.pm at sensor positions in samples.inp: |
| 711 |
+ |
.IP "" .2i |
| 712 |
+ |
rtrace -h -ov -ab 1 -ap global.pm 50 -ap caustic.pm 50 scene.oct < |
| 713 |
+ |
samples.inp > illum.out |
| 714 |
|
.SH ENVIRONMENT |
| 715 |
|
RAYPATH the directories to check for auxiliary files. |
| 716 |
|
.SH FILES |
| 728 |
|
.SH AUTHOR |
| 729 |
|
Greg Ward |
| 730 |
|
.SH "SEE ALSO" |
| 731 |
< |
getinfo(1), lookamb(1), oconv(1), pfilt(1), pinterp(1), |
| 731 |
> |
getinfo(1), lookamb(1), mkpmap(1), oconv(1), pfilt(1), pinterp(1), |
| 732 |
|
pvalue(1), rpict(1), rcontrib(1), rvu(1), vwrays(1), ximage(1) |
