| 30 |
|
If the direction vector is (0,0,0), a bogus record |
| 31 |
|
is printed and the output is flushed if the |
| 32 |
|
.I -x |
| 33 |
< |
value is unset or zero. |
| 33 |
> |
value is one or zero. |
| 34 |
|
(See the notes on this option below.)\0 |
| 35 |
|
This may be useful for programs that run |
| 36 |
|
.I rtrace |
| 87 |
|
.IP |
| 88 |
|
v value (radiance) |
| 89 |
|
.IP |
| 90 |
+ |
V contribution (radiance) |
| 91 |
+ |
.IP |
| 92 |
|
w weight |
| 93 |
|
.IP |
| 94 |
|
W color coefficient |
| 180 |
|
This option is especially useful in |
| 181 |
|
conjunction with ximage(1) for computing illuminance at scene points. |
| 182 |
|
.TP |
| 183 |
< |
.BR \-R |
| 184 |
< |
Boolean switch to control random sampling. |
| 183 |
> |
.BR \-u |
| 184 |
> |
Boolean switch to control uncorrelated random sampling. |
| 185 |
|
When "off", a low-discrepancy sequence is used, which reduces |
| 186 |
|
variance but can result in a brushed appearance in specular highlights. |
| 187 |
|
When "on", pure Monte Carlo sampling is used in all calculations. |
| 199 |
|
.I res. |
| 200 |
|
The output will be flushed after every |
| 201 |
|
.I res |
| 202 |
< |
input rays. |
| 202 |
> |
input rays if |
| 203 |
> |
.I \-y |
| 204 |
> |
is set to zero. |
| 205 |
> |
A value of one means that every ray will be flushed, whatever |
| 206 |
> |
the setting of |
| 207 |
> |
.I \-y. |
| 208 |
|
A value of zero means that no output flushing will take place. |
| 209 |
|
.TP |
| 210 |
|
.BI -y \ res |
| 235 |
|
.I \-f |
| 236 |
|
option, above.) |
| 237 |
|
.TP |
| 238 |
+ |
.BI -n \ nproc |
| 239 |
+ |
Execute in parallel on |
| 240 |
+ |
.I nproc |
| 241 |
+ |
local processes. |
| 242 |
+ |
This option is incompatible with the |
| 243 |
+ |
.I \-P |
| 244 |
+ |
and |
| 245 |
+ |
.I \-PP, |
| 246 |
+ |
options. |
| 247 |
+ |
Multiple processes also do not work properly with ray tree output |
| 248 |
+ |
using any of the |
| 249 |
+ |
.I \-o*t* |
| 250 |
+ |
options. |
| 251 |
+ |
There is no benefit from specifying more processes than there are |
| 252 |
+ |
cores available on the system or the |
| 253 |
+ |
.I \-x |
| 254 |
+ |
setting, which forces a wait at each flush. |
| 255 |
+ |
.TP |
| 256 |
|
.BI -dj \ frac |
| 257 |
|
Set the direct jittering to |
| 258 |
|
.I frac. |
| 335 |
|
.I \-i |
| 336 |
|
option. |
| 337 |
|
.TP |
| 338 |
< |
.BI -sj \ frac |
| 339 |
< |
Set the specular sampling jitter to |
| 340 |
< |
.I frac. |
| 341 |
< |
This is the degree to which the highlights are sampled |
| 342 |
< |
for rough specular materials. |
| 343 |
< |
A value of one means that all highlights will be fully sampled |
| 344 |
< |
using distributed ray tracing. |
| 338 |
> |
.BI -ss \ samp |
| 339 |
> |
Set the specular sampling to |
| 340 |
> |
.I samp. |
| 341 |
> |
For values less than 1, this is the degree to which the highlights |
| 342 |
> |
are sampled for rough specular materials. |
| 343 |
> |
A value greater than one causes multiple ray samples to be sent |
| 344 |
> |
to reduce noise at a commmesurate cost. |
| 345 |
|
A value of zero means that no jittering will take place, and all |
| 346 |
|
reflections will appear sharp even when they should be diffuse. |
| 347 |
|
.TP |
| 361 |
|
.TP |
| 362 |
|
.BR -bv |
| 363 |
|
Boolean switch for back face visibility. |
| 364 |
< |
With this switch off, back faces of opaque objects will be invisible |
| 365 |
< |
to all rays. |
| 364 |
> |
With this switch off, back faces of all objects will be invisible |
| 365 |
> |
to view rays. |
| 366 |
|
This is dangerous unless the model was constructed such that |
| 367 |
< |
all surface normals on opaque objects face outward. |
| 367 |
> |
all surface normals face outward. |
| 368 |
|
Although turning off back face visibility does not save much |
| 369 |
|
computation time under most circumstances, it may be useful as a |
| 370 |
|
tool for scene debugging, or for seeing through one-sided walls from |
| 371 |
|
the outside. |
| 347 |
– |
This option has no effect on transparent or translucent materials. |
| 372 |
|
.TP |
| 373 |
|
.BI -av " red grn blu" |
| 374 |
|
Set the ambient value to a radiance of |
| 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 |
> |
This value defaults to 1 in photon mapping mode (see |
| 408 |
> |
.I -ap |
| 409 |
> |
below), implying that global photon irradiance is always computed via |
| 410 |
> |
.I one |
| 411 |
> |
ambient bounce; this behaviour applies to any positive number of ambient |
| 412 |
> |
bounces, regardless of the actual value specified. A negative value enables |
| 413 |
> |
a preview mode that directly visualises the irradiance from the global |
| 414 |
> |
photon map without any ambient 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 |
+ |
Maximum search radius for photon map lookups. Without this option, an |
| 557 |
+ |
initial maximum search radius is estimated for each photon map from the |
| 558 |
+ |
average photon distance to the distribution's centre of gravity. It is then |
| 559 |
+ |
adapted to the photon density in subsequent lookups. This option imposes a |
| 560 |
+ |
global fixed maximum search radius for |
| 561 |
+ |
.I all |
| 562 |
+ |
photon maps, thus defeating the automatic adaptation. It is useful when |
| 563 |
+ |
multiple warnings about short photon lookups are issued. Note that this |
| 564 |
+ |
option does not conflict with the bandwidth specified with the |
| 565 |
+ |
.I \-ap |
| 566 |
+ |
option; the number of photons found will not exceed the latter, but may be |
| 567 |
+ |
lower if the maximum search radius contains fewer photons, thus resulting in |
| 568 |
+ |
short lookups. Setting this radius too large, on the other hand, may |
| 569 |
+ |
degrade performance. |
| 570 |
+ |
.TP |
| 571 |
+ |
.BI -ac " pagesize" |
| 572 |
+ |
Set the photon cache page size when using out-of-core photon mapping. The |
| 573 |
+ |
photon cache reduces disk I/O incurred by on-demand loading (paging) of |
| 574 |
+ |
photons, and thus increases performance. This |
| 575 |
+ |
is expressed as a (float) multiple of the density estimate bandwidth |
| 576 |
+ |
specified with |
| 577 |
+ |
.I \-ap |
| 578 |
+ |
under the assumption that photon lookups are local to a cache page. Cache |
| 579 |
+ |
performance is sensitive to this parameter: larger pagesizes will reduce the |
| 580 |
+ |
paging frequency at the expense of higher latency when paging does occur. |
| 581 |
+ |
Sensible values are in the range 4 (default) to 16. |
| 582 |
+ |
.TP |
| 583 |
+ |
.BI -aC " cachesize" |
| 584 |
+ |
Set the total number of photons cached when using out-of-core photon |
| 585 |
+ |
mapping, taking into account the pagesize specified by |
| 586 |
+ |
.I \-ac. |
| 587 |
+ |
Note that this is approximate as the number of cache pages is rounded to |
| 588 |
+ |
the nearest prime. This allows adapting the cache to the available physical |
| 589 |
+ |
memory. In conjunction with the |
| 590 |
+ |
.I \-n |
| 591 |
+ |
option, this is the cache size |
| 592 |
+ |
.I per parallel process. |
| 593 |
+ |
Cache performance is less sensitive to this parameter, |
| 594 |
+ |
and reasonable performance can obtained with as few as 10k photons. The |
| 595 |
+ |
default is 1M. This option recognises multiplier suffixes (k = 1e3, M = |
| 596 |
+ |
1e6), both in upper and lower case. |
| 597 |
+ |
.TP |
| 598 |
|
.BI -me " rext gext bext" |
| 599 |
|
Set the global medium extinction coefficient to the indicated color, |
| 600 |
|
in units of 1/distance (distance in world coordinates). |
| 633 |
|
.TP |
| 634 |
|
.BI -lr \ N |
| 635 |
|
Limit reflections to a maximum of |
| 636 |
< |
.I N. |
| 636 |
> |
.I N, |
| 637 |
> |
if N is a positive integer. |
| 638 |
|
If |
| 639 |
|
.I N |
| 640 |
|
is zero or negative, then Russian roulette is used for ray |
| 642 |
|
.I -lw |
| 643 |
|
setting (below) must be positive. |
| 644 |
|
If N is a negative integer, then this sets the upper limit |
| 645 |
< |
of reflections past which Russian roulette will not be used. |
| 645 |
> |
of reflections past which Russian roulette will be used. |
| 646 |
|
In scenes with dielectrics and total internal reflection, |
| 647 |
|
a setting of 0 (no limit) may cause a stack overflow. |
| 648 |
|
.TP |
| 718 |
|
on most multiprocessing platforms, since the |
| 719 |
|
.I fork(2) |
| 720 |
|
system call will share memory on a copy-on-write basis. |
| 721 |
+ |
.SH NOTES |
| 722 |
+ |
Photons are generally surface bound (an exception are volume photons), thus |
| 723 |
+ |
the ambient irradiance in photon mapping mode will be biased at positions |
| 724 |
+ |
which do not lie on a surface. |
| 725 |
|
.SH EXAMPLES |
| 726 |
|
To compute radiance values for the rays listed in samples.inp: |
| 727 |
|
.IP "" .2i |
| 728 |
< |
rtrace -ov scene.oct < samples.inp > radiance.out |
| 728 |
> |
rtrace \-ov scene.oct < samples.inp > radiance.out |
| 729 |
|
.PP |
| 730 |
|
To compute illuminance values at locations selected with the 't' |
| 731 |
|
command of |
| 732 |
|
.I ximage(1): |
| 733 |
|
.IP "" .2i |
| 734 |
< |
ximage scene.pic | rtrace -h -x 1 -i scene.oct | rcalc -e '$1=47.4*$1+120*$2+11.6*$3' |
| 734 |
> |
ximage scene.hdr | rtrace \-h \-x 1 \-i scene.oct | rcalc \-e '$1=47.4*$1+120*$2+11.6*$3' |
| 735 |
|
.PP |
| 736 |
|
To record the object identifier corresponding to each pixel in an image: |
| 737 |
|
.IP "" .2i |
| 738 |
< |
vwrays -fd scene.pic | rtrace -fda `vwrays -d scene.pic` -os scene.oct |
| 738 |
> |
vwrays \-fd scene.hdr | rtrace \-fda `vwrays \-d scene.hdr` \-os scene.oct |
| 739 |
|
.PP |
| 740 |
|
To compute an image with an unusual view mapping: |
| 741 |
|
.IP "" .2i |
| 742 |
< |
cnt 640 480 | rcalc -e 'xr:640;yr:480' -f unusual_view.cal | rtrace |
| 743 |
< |
-x 640 -y 480 -fac scene.oct > unusual.pic |
| 742 |
> |
cnt 480 640 | rcalc \-e 'xr:640;yr:480' \-f unusual_view.cal | rtrace |
| 743 |
> |
\-x 640 \-y 480 \-fac scene.oct > unusual.hdr |
| 744 |
> |
.PP |
| 745 |
> |
To compute ambient illuminance in photon mapping mode from a global photon |
| 746 |
> |
map global.pm via one ambient bounce, and from a caustic photon map |
| 747 |
> |
caustic.pm at sensor positions in samples.inp: |
| 748 |
> |
.IP "" .2i |
| 749 |
> |
rtrace -h -ov -ab 1 -ap global.pm 50 -ap caustic.pm 50 scene.oct < |
| 750 |
> |
samples.inp > illum.out |
| 751 |
|
.SH ENVIRONMENT |
| 752 |
|
RAYPATH the directories to check for auxiliary files. |
| 753 |
|
.SH FILES |
| 765 |
|
.SH AUTHOR |
| 766 |
|
Greg Ward |
| 767 |
|
.SH "SEE ALSO" |
| 768 |
< |
getinfo(1), lookamb(1), oconv(1), pfilt(1), pinterp(1), |
| 769 |
< |
pvalue(1), rpict(1), rtcontrib(1), rvu(1), vwrays(1), ximage(1) |
| 768 |
> |
getinfo(1), lookamb(1), mkpmap(1), oconv(1), pfilt(1), pinterp(1), |
| 769 |
> |
pvalue(1), rpict(1), rcontrib(1), rvu(1), vwrays(1), ximage(1) |
