| 87 |
|
.IP |
| 88 |
|
v value (radiance) |
| 89 |
|
.IP |
| 90 |
+ |
V contribution (radiance) |
| 91 |
+ |
.IP |
| 92 |
|
w weight |
| 93 |
|
.IP |
| 94 |
< |
W contribution |
| 94 |
> |
W color coefficient |
| 95 |
|
.IP |
| 96 |
|
l effective length of ray |
| 97 |
|
.IP |
| 180 |
|
This option is especially useful in |
| 181 |
|
conjunction with ximage(1) for computing illuminance at scene points. |
| 182 |
|
.TP |
| 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. |
| 188 |
+ |
.TP |
| 189 |
|
.BR \-I |
| 190 |
|
Boolean switch to compute irradiance rather than radiance, |
| 191 |
|
with the input origin and direction interpreted instead |
| 526 |
|
.BI -lr \ N |
| 527 |
|
Limit reflections to a maximum of |
| 528 |
|
.I N. |
| 529 |
+ |
If |
| 530 |
+ |
.I N |
| 531 |
+ |
is zero or negative, then Russian roulette is used for ray |
| 532 |
+ |
termination, and the |
| 533 |
+ |
.I -lw |
| 534 |
+ |
setting (below) must be positive. |
| 535 |
+ |
If N is a negative integer, then this sets the upper limit |
| 536 |
+ |
of reflections past which Russian roulette will not be used. |
| 537 |
+ |
In scenes with dielectrics and total internal reflection, |
| 538 |
+ |
a setting of 0 (no limit) may cause a stack overflow. |
| 539 |
|
.TP |
| 540 |
|
.BI -lw \ frac |
| 541 |
|
Limit the weight of each ray to a minimum of |
| 542 |
|
.I frac. |
| 543 |
< |
During ray-tracing, a record is kept of the final contribution |
| 544 |
< |
a ray would have to the image. |
| 545 |
< |
If it is less then the specified minimum, the ray is not traced. |
| 543 |
> |
During ray-tracing, a record is kept of the estimated contribution |
| 544 |
> |
(weight) a ray would have in the image. |
| 545 |
> |
If this weight is less than the specified minimum and the |
| 546 |
> |
.I -lr |
| 547 |
> |
setting (above) is positive, the ray is not traced. |
| 548 |
> |
Otherwise, Russian roulette is used to |
| 549 |
> |
continue rays with a probability equal to the ray weight |
| 550 |
> |
divided by the given |
| 551 |
> |
.I frac. |
| 552 |
|
.TP |
| 553 |
|
.BR -ld |
| 554 |
|
Boolean switch to limit ray distance. |
| 612 |
|
.SH EXAMPLES |
| 613 |
|
To compute radiance values for the rays listed in samples.inp: |
| 614 |
|
.IP "" .2i |
| 615 |
< |
rtrace -ov scene.oct < samples.inp > radiance.out |
| 615 |
> |
rtrace \-ov scene.oct < samples.inp > radiance.out |
| 616 |
|
.PP |
| 617 |
|
To compute illuminance values at locations selected with the 't' |
| 618 |
|
command of |
| 619 |
|
.I ximage(1): |
| 620 |
|
.IP "" .2i |
| 621 |
< |
ximage scene.pic | rtrace -h -x 1 -i scene.oct | rcalc -e '$1=47.4*$1+120*$2+11.6*$3' |
| 621 |
> |
ximage scene.hdr | rtrace \-h \-x 1 \-i scene.oct | rcalc \-e '$1=47.4*$1+120*$2+11.6*$3' |
| 622 |
|
.PP |
| 623 |
|
To record the object identifier corresponding to each pixel in an image: |
| 624 |
|
.IP "" .2i |
| 625 |
< |
vwrays -fd scene.pic | rtrace -fda `vwrays -d scene.pic` -os scene.oct |
| 625 |
> |
vwrays \-fd scene.hdr | rtrace \-fda `vwrays \-d scene.hdr` \-os scene.oct |
| 626 |
|
.PP |
| 627 |
|
To compute an image with an unusual view mapping: |
| 628 |
|
.IP "" .2i |
| 629 |
< |
cnt 640 480 | rcalc -e 'xr:640;yr:480' -f unusual_view.cal | rtrace |
| 630 |
< |
-x 640 -y 480 -fac scene.oct > unusual.pic |
| 629 |
> |
cnt 480 640 | rcalc \-e 'xr:640;yr:480' \-f unusual_view.cal | rtrace |
| 630 |
> |
\-x 640 \-y 480 \-fac scene.oct > unusual.hdr |
| 631 |
|
.SH ENVIRONMENT |
| 632 |
|
RAYPATH the directories to check for auxiliary files. |
| 633 |
|
.SH FILES |
