| 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 |
| 111 |
|
.IP |
| 112 |
|
M material name |
| 113 |
|
.IP |
| 114 |
+ |
r mirrored value contribution |
| 115 |
+ |
.IP |
| 116 |
+ |
x unmirrored value contribution |
| 117 |
+ |
.IP |
| 118 |
+ |
R mirrored ray length |
| 119 |
+ |
.IP |
| 120 |
+ |
X unmirrored ray length |
| 121 |
+ |
.IP |
| 122 |
|
~ tilde (end of trace marker) |
| 123 |
|
.IP |
| 124 |
|
If the letter 't' appears in |
| 207 |
|
.I res. |
| 208 |
|
The output will be flushed after every |
| 209 |
|
.I res |
| 210 |
< |
input rays. |
| 210 |
> |
input rays if |
| 211 |
> |
.I \-y |
| 212 |
> |
is set to zero. |
| 213 |
> |
A value of one means that every ray will be flushed, whatever |
| 214 |
> |
the setting of |
| 215 |
> |
.I \-y. |
| 216 |
|
A value of zero means that no output flushing will take place. |
| 217 |
|
.TP |
| 218 |
|
.BI -y \ res |
| 343 |
|
.I \-i |
| 344 |
|
option. |
| 345 |
|
.TP |
| 346 |
< |
.BI -sj \ frac |
| 347 |
< |
Set the specular sampling jitter to |
| 348 |
< |
.I frac. |
| 349 |
< |
This is the degree to which the highlights are sampled |
| 350 |
< |
for rough specular materials. |
| 351 |
< |
A value of one means that all highlights will be fully sampled |
| 352 |
< |
using distributed ray tracing. |
| 346 |
> |
.BI -ss \ samp |
| 347 |
> |
Set the specular sampling to |
| 348 |
> |
.I samp. |
| 349 |
> |
For values less than 1, this is the degree to which the highlights |
| 350 |
> |
are sampled for rough specular materials. |
| 351 |
> |
A value greater than one causes multiple ray samples to be sent |
| 352 |
> |
to reduce noise at a commmesurate cost. |
| 353 |
|
A value of zero means that no jittering will take place, and all |
| 354 |
|
reflections will appear sharp even when they should be diffuse. |
| 355 |
|
.TP |
| 369 |
|
.TP |
| 370 |
|
.BR -bv |
| 371 |
|
Boolean switch for back face visibility. |
| 372 |
< |
With this switch off, back faces of opaque objects will be invisible |
| 373 |
< |
to all rays. |
| 372 |
> |
With this switch off, back faces of all objects will be invisible |
| 373 |
> |
to view rays. |
| 374 |
|
This is dangerous unless the model was constructed such that |
| 375 |
< |
all surface normals on opaque objects face outward. |
| 375 |
> |
all surface normals face outward. |
| 376 |
|
Although turning off back face visibility does not save much |
| 377 |
|
computation time under most circumstances, it may be useful as a |
| 378 |
|
tool for scene debugging, or for seeing through one-sided walls from |
| 379 |
|
the outside. |
| 367 |
– |
This option has no effect on transparent or translucent materials. |
| 380 |
|
.TP |
| 381 |
|
.BI -av " red grn blu" |
| 382 |
|
Set the ambient value to a radiance of |
| 409 |
|
.BI -ab \ N |
| 410 |
|
Set the number of ambient bounces to |
| 411 |
|
.I N. |
| 412 |
< |
This is the maximum number of diffuse bounces |
| 413 |
< |
computed by the indirect calculation. |
| 414 |
< |
A value of zero implies no indirect calculation. |
| 412 |
> |
This is the maximum number of diffuse bounces computed by the indirect |
| 413 |
> |
calculation. A value of zero implies no indirect calculation. |
| 414 |
> |
.IP |
| 415 |
> |
This value defaults to 1 in photon mapping mode (see |
| 416 |
> |
.I -ap |
| 417 |
> |
below), implying that global photon irradiance is always computed via |
| 418 |
> |
.I one |
| 419 |
> |
ambient bounce; this behaviour applies to any positive number of ambient |
| 420 |
> |
bounces, regardless of the actual value specified. A negative value enables |
| 421 |
> |
a preview mode that directly visualises the irradiance from the global |
| 422 |
> |
photon map without any ambient bounces. |
| 423 |
|
.TP |
| 424 |
|
.BI -ar \ res |
| 425 |
|
Set the ambient resolution to |
| 525 |
|
except read modifiers to be included from |
| 526 |
|
.I file. |
| 527 |
|
.TP |
| 528 |
+ |
.BI -ap " file [bwidth1 [bwidth2]]" |
| 529 |
+ |
Enable photon mapping mode. Loads a photon map generated with |
| 530 |
+ |
.I mkpmap(1) |
| 531 |
+ |
from |
| 532 |
+ |
.I file, |
| 533 |
+ |
and evaluates the indirect irradiance depending on the photon type |
| 534 |
+ |
(automagically detected) using density estimates with a bandwidth of |
| 535 |
+ |
.I bwidth1 |
| 536 |
+ |
photons, or the default bandwidth if none is specified (a warning will be |
| 537 |
+ |
issued in this case). |
| 538 |
+ |
.IP |
| 539 |
+ |
Global photon irradiance is evaluated as part of the ambient calculation (see |
| 540 |
+ |
.I \-ab |
| 541 |
+ |
above), caustic photon irradiance is evaluated at primary rays, and |
| 542 |
+ |
indirect inscattering in |
| 543 |
+ |
.I mist |
| 544 |
+ |
is accounted for by volume photons. Contribution photons are treated as |
| 545 |
+ |
global photons by |
| 546 |
+ |
.I rtrace. |
| 547 |
+ |
.IP |
| 548 |
+ |
Additionally specifying |
| 549 |
+ |
.I bwidth2 |
| 550 |
+ |
enables bias compensation for the density estimates with a |
| 551 |
+ |
minimum and maximum bandwidth of |
| 552 |
+ |
.I bwidth1 |
| 553 |
+ |
and |
| 554 |
+ |
.I bwidth2, |
| 555 |
+ |
respectively. |
| 556 |
+ |
.IP |
| 557 |
+ |
Global photon irradiance may be optionally precomputed by |
| 558 |
+ |
.I mkpmap(1), |
| 559 |
+ |
in which case the bandwidth, if specified, is ignored, as the nearest photon |
| 560 |
+ |
is invariably looked up. |
| 561 |
+ |
.IP |
| 562 |
+ |
Using direct photons replaces the direct calculation with density estimates |
| 563 |
+ |
for debugging and validation of photon emission. |
| 564 |
+ |
.TP |
| 565 |
+ |
.BI -am " frac" |
| 566 |
+ |
Maximum search radius for photon map lookups. Without this option, an |
| 567 |
+ |
initial maximum search radius is estimated for each photon map from the |
| 568 |
+ |
average photon distance to the distribution's centre of gravity. It is then |
| 569 |
+ |
adapted to the photon density in subsequent lookups. This option imposes a |
| 570 |
+ |
global fixed maximum search radius for |
| 571 |
+ |
.I all |
| 572 |
+ |
photon maps, thus defeating the automatic adaptation. It is useful when |
| 573 |
+ |
multiple warnings about short photon lookups are issued. Note that this |
| 574 |
+ |
option does not conflict with the bandwidth specified with the |
| 575 |
+ |
.I \-ap |
| 576 |
+ |
option; the number of photons found will not exceed the latter, but may be |
| 577 |
+ |
lower if the maximum search radius contains fewer photons, thus resulting in |
| 578 |
+ |
short lookups. Setting this radius too large, on the other hand, may |
| 579 |
+ |
degrade performance. |
| 580 |
+ |
.TP |
| 581 |
+ |
.BI -ac " pagesize" |
| 582 |
+ |
Set the photon cache page size when using out-of-core photon mapping. The |
| 583 |
+ |
photon cache reduces disk I/O incurred by on-demand loading (paging) of |
| 584 |
+ |
photons, and thus increases performance. This |
| 585 |
+ |
is expressed as a (float) multiple of the density estimate bandwidth |
| 586 |
+ |
specified with |
| 587 |
+ |
.I \-ap |
| 588 |
+ |
under the assumption that photon lookups are local to a cache page. Cache |
| 589 |
+ |
performance is sensitive to this parameter: larger pagesizes will reduce the |
| 590 |
+ |
paging frequency at the expense of higher latency when paging does occur. |
| 591 |
+ |
Sensible values are in the range 4 (default) to 16. |
| 592 |
+ |
.TP |
| 593 |
+ |
.BI -aC " cachesize" |
| 594 |
+ |
Set the total number of photons cached when using out-of-core photon |
| 595 |
+ |
mapping, taking into account the pagesize specified by |
| 596 |
+ |
.I \-ac. |
| 597 |
+ |
Note that this is approximate as the number of cache pages is rounded to |
| 598 |
+ |
the nearest prime. This allows adapting the cache to the available physical |
| 599 |
+ |
memory. In conjunction with the |
| 600 |
+ |
.I \-n |
| 601 |
+ |
option, this is the cache size |
| 602 |
+ |
.I per parallel process. |
| 603 |
+ |
Cache performance is less sensitive to this parameter, |
| 604 |
+ |
and reasonable performance can obtained with as few as 10k photons. The |
| 605 |
+ |
default is 1M. This option recognises multiplier suffixes (k = 1e3, M = |
| 606 |
+ |
1e6), both in upper and lower case. |
| 607 |
+ |
.TP |
| 608 |
|
.BI -me " rext gext bext" |
| 609 |
|
Set the global medium extinction coefficient to the indicated color, |
| 610 |
|
in units of 1/distance (distance in world coordinates). |
| 643 |
|
.TP |
| 644 |
|
.BI -lr \ N |
| 645 |
|
Limit reflections to a maximum of |
| 646 |
< |
.I N. |
| 646 |
> |
.I N, |
| 647 |
> |
if N is a positive integer. |
| 648 |
|
If |
| 649 |
|
.I N |
| 650 |
|
is zero or negative, then Russian roulette is used for ray |
| 652 |
|
.I -lw |
| 653 |
|
setting (below) must be positive. |
| 654 |
|
If N is a negative integer, then this sets the upper limit |
| 655 |
< |
of reflections past which Russian roulette will not be used. |
| 655 |
> |
of reflections past which Russian roulette will be used. |
| 656 |
|
In scenes with dielectrics and total internal reflection, |
| 657 |
|
a setting of 0 (no limit) may cause a stack overflow. |
| 658 |
|
.TP |
| 728 |
|
on most multiprocessing platforms, since the |
| 729 |
|
.I fork(2) |
| 730 |
|
system call will share memory on a copy-on-write basis. |
| 731 |
+ |
.SH NOTES |
| 732 |
+ |
Photons are generally surface bound (an exception are volume photons), thus |
| 733 |
+ |
the ambient irradiance in photon mapping mode will be biased at positions |
| 734 |
+ |
which do not lie on a surface. |
| 735 |
|
.SH EXAMPLES |
| 736 |
|
To compute radiance values for the rays listed in samples.inp: |
| 737 |
|
.IP "" .2i |
| 751 |
|
.IP "" .2i |
| 752 |
|
cnt 480 640 | rcalc \-e 'xr:640;yr:480' \-f unusual_view.cal | rtrace |
| 753 |
|
\-x 640 \-y 480 \-fac scene.oct > unusual.hdr |
| 754 |
+ |
.PP |
| 755 |
+ |
To compute ambient illuminance in photon mapping mode from a global photon |
| 756 |
+ |
map global.pm via one ambient bounce, and from a caustic photon map |
| 757 |
+ |
caustic.pm at sensor positions in samples.inp: |
| 758 |
+ |
.IP "" .2i |
| 759 |
+ |
rtrace -h -ov -ab 1 -ap global.pm 50 -ap caustic.pm 50 scene.oct < |
| 760 |
+ |
samples.inp > illum.out |
| 761 |
|
.SH ENVIRONMENT |
| 762 |
|
RAYPATH the directories to check for auxiliary files. |
| 763 |
|
.SH FILES |
| 775 |
|
.SH AUTHOR |
| 776 |
|
Greg Ward |
| 777 |
|
.SH "SEE ALSO" |
| 778 |
< |
getinfo(1), lookamb(1), oconv(1), pfilt(1), pinterp(1), |
| 779 |
< |
pvalue(1), rpict(1), rtcontrib(1), rvu(1), vwrays(1), ximage(1) |
| 778 |
> |
getinfo(1), lookamb(1), mkpmap(1), oconv(1), pfilt(1), pinterp(1), |
| 779 |
> |
pvalue(1), rcontrib(1), rpict(1), rtpict(1), rvu(1), vwrays(1), ximage(1) |
