| 57 |
|
illumination and is intended for debugging and validation of photon emission |
| 58 |
|
from the light sources, as the quality is too low for actual rendering. |
| 59 |
|
|
| 60 |
< |
.IP "\fB\-apC \fIfile nphotons \fB(EXPERIMENTAL)\fR" |
| 60 |
> |
.IP "\fB\-apC \fIfile nphotons\fR" |
| 61 |
|
Generate a contribution photon map containing approximately |
| 62 |
|
\fInphotons\fR photons, and output to file \fIfile\fR. This may then be |
| 63 |
< |
used by \fIrcontrib(1)\fR to compute light source contributions. |
| 63 |
> |
used by \fIrcontrib(1)\fR to compute light source contributions. When used |
| 64 |
> |
with \fIrtrace(1)\fR or \fIrpict(1)\fR, contribution photon maps behave as |
| 65 |
> |
regular global photon maps and yield cumulative contributions from all light |
| 66 |
> |
sources. |
| 67 |
|
.IP |
| 68 |
|
With this option, \fImkpmap\fR uses a modified photon distribution |
| 69 |
|
algorithm that ensures all light sources contribute approximately the |
| 84 |
|
photon flux; the remaining photons are discarded as their contributions |
| 85 |
|
have been accounted for. |
| 86 |
|
.IP |
| 87 |
< |
This obviates the explicit irradiance |
| 88 |
< |
evaluation by \fIrpict(1), rtrace(1)\fR and \fIrvu(1)\fR, thus providing |
| 89 |
< |
a speedup at the expense of accuracy. The resulting error is tolerable |
| 90 |
< |
if the indirect illumination has a low gradient, as is usually the case |
| 88 |
< |
with diffuse illumination. |
| 87 |
> |
This obviates the explicit irradiance evaluation by \fIrpict(1), |
| 88 |
> |
rtrace(1)\fR and \fIrvu(1)\fR, thus providing a speedup at the expense of |
| 89 |
> |
accuracy. The resulting error is tolerable if the indirect illumination has |
| 90 |
> |
a low gradient, as is usually the case with diffuse illumination. |
| 91 |
|
|
| 92 |
|
.IP "\fB\-apD \fIpredistrib\fR" |
| 93 |
|
Photon predistribution factor; this is the fraction of \fInphotons\fR |
| 95 |
|
remaining number of photons to emit in the main pass to approximately |
| 96 |
|
yield a photon map of size \fInphotons\fR. |
| 97 |
|
.IP |
| 98 |
< |
Setting this too high may |
| 99 |
< |
yield more than \fInphotons\fR in the initial pass with highly |
| 100 |
< |
reflective geometry. Note that this value may exceed 1, which may be |
| 99 |
< |
useful if the resulting photon map size greatly deviates from |
| 98 |
> |
Setting this too high may yield more than \fInphotons\fR in the initial pass |
| 99 |
> |
with highly reflective geometry. Note that this value may exceed 1, which |
| 100 |
> |
may be useful if the resulting photon map size greatly deviates from |
| 101 |
|
\fInphotons\fR with a very low average reflectance. |
| 102 |
|
|
| 103 |
< |
.IP "\fB\-apP \fIprecomp\fR" |
| 104 |
< |
Fraction of global photons to precompute in the range ]0,1] when using the |
| 105 |
< |
\fB\-app\fR option. |
| 103 |
> |
.IP "\fB\-api \fIxmin ymin zmin xmax ymax zmax\fR" |
| 104 |
> |
Define a region of interested within which to store photons exclusively; |
| 105 |
> |
photons will only be stored within the volume bounded by the given minimum |
| 106 |
> |
and maximum coordinates. Multiple instances of this option may be specified |
| 107 |
> |
with cumulative effect to define compound regions of interest. This is |
| 108 |
> |
useful for constraining photons to only the relevant regions of a scene, but |
| 109 |
> |
may increase the photon distribution time. |
| 110 |
> |
.IP |
| 111 |
> |
\fBWARNING: this is an optimisation option for advanced users (an elite |
| 112 |
> |
group collectively known as \fIZe Ekspertz\fB) and may yield biased results. |
| 113 |
> |
Use with caution!\fR |
| 114 |
|
|
| 115 |
|
.IP "\fB\-apm \fImaxbounce\fR" |
| 116 |
< |
Maximum number of bounces (scattering events) along a photon path before |
| 117 |
< |
being considered "runaway" and terminated. Photons paths are normally |
| 109 |
< |
terminated via \fIRussian Roulette\fR, depending on their albedo. With |
| 110 |
< |
unrealistically high albedos, this is not guaranteed, and this options |
| 111 |
< |
imposes a hard limit to avoid an infinite loop. |
| 116 |
> |
Synonymous with \fB\-lr\fR for backwards compatibility. May be removed in |
| 117 |
> |
future releases. |
| 118 |
|
|
| 119 |
|
.IP "\fB\-apM \fImaxprepass\fR" |
| 120 |
|
Maximum number of iterations of the distribution prepass before terminating |
| 130 |
|
space which separates them from the emitting light source via an |
| 131 |
|
opening, or port. |
| 132 |
|
.IP |
| 133 |
< |
A typical application is daylight simulation, where a |
| 134 |
< |
fenestration acts as port to admit photons into an interior after |
| 135 |
< |
emission from an external light source. Multiple instances of this |
| 130 |
< |
option may be specified. |
| 133 |
> |
A typical application is daylight simulation, where a fenestration acts as |
| 134 |
> |
port to admit photons into an interior after emission from an external light |
| 135 |
> |
source. Multiple instances of this option may be specified. |
| 136 |
|
.IP |
| 137 |
|
Note that port objects must be defined with their surface normals |
| 138 |
|
pointing \fIinside\fR as per \fImkillum\fR convention. |
| 141 |
|
Read photon port modifiers from the file \fImodfile\fR as a more convenient |
| 142 |
|
alternative to multiple instances of \fB\-apo\fR. |
| 143 |
|
|
| 144 |
+ |
.IP "\fB\-apP \fIprecomp\fR" |
| 145 |
+ |
Fraction of global photons to precompute in the range ]0,1] when using the |
| 146 |
+ |
\fB\-app\fR option. |
| 147 |
+ |
|
| 148 |
|
.IP "\fB\-apr \fIseed\fR" |
| 149 |
|
Seed for the random number generator. This is necessary for generating |
| 150 |
|
different photon distributions for the same octree and photon map size. |
| 151 |
|
|
| 152 |
|
.IP "\fB\-aps \fImod\fR" |
| 153 |
|
Specifies a modifier \fImod\fR defined as \fIantimatter\fR material to act |
| 154 |
< |
as a dummy (i.e. invisible) sensor surface. Photons will be deposited on |
| 154 |
> |
as a virtual (i.e. invisible) receiver surface. Photons will be deposited on |
| 155 |
|
all surfaces using this modifier, just like regular materials, but will then |
| 156 |
|
be transferred through the surface without undergoing scattering; the |
| 157 |
|
surface therefore does not affect the light transport and simply acts as an |
| 158 |
|
invisible photon receiver. This is useful when photon irradiance is to be |
| 159 |
|
evaluated at points which do not lie on regular geometry, e.g. at workplane |
| 160 |
< |
height with \firtrace\fR's \fB-I\fR option. Without this workaround, |
| 160 |
> |
height with \fIrtrace\fR's \fB-I\fR option. Without this workaround, |
| 161 |
|
photons would be collected from parallel but distant planes, leading to |
| 162 |
|
underestimation. Note that photons are only deposited when incident from |
| 163 |
|
the front side of the sensor surface, i.e. when entering the |
| 165 |
|
an error if the specified modifier is not an \fIantimatter\fR material. |
| 166 |
|
|
| 167 |
|
.IP "\fB\-apS \fImodfile\fR" |
| 168 |
< |
Read dummy sensor surface modifiers from the file \fImodfile\fR as a more |
| 168 |
> |
Read virtual receiver surface modifiers from the file \fImodfile\fR as a more |
| 169 |
|
convenient alternative to multiple instances of \fB\-aps\fR. |
| 170 |
|
|
| 171 |
|
.IP "\fB\-bv\fR[\fB+\fR|\fB-\fR]" |
| 199 |
|
inadvertently destroying the results of potentially lengthy photon |
| 200 |
|
mapping runs. |
| 201 |
|
|
| 202 |
< |
.IP "\fB\-i \fIinc\fR" |
| 203 |
< |
Photon heap size increment; the photon heap is enlarged by this amount |
| 204 |
< |
when storage overflows during photon distribution. No need to fiddle |
| 205 |
< |
with this under ordinary circumstances. |
| 202 |
> |
.IP "\fB\-ld \fImaxdist\fR" |
| 203 |
> |
Limit cumulative distance travelled by a photon along its path to |
| 204 |
> |
\fImaxdist\fR. Photon hits within this distance will be stored, and the |
| 205 |
> |
photon is terminated once its path length exceeds this limit. This is |
| 206 |
> |
useful for setting radial regions of interest around emitting/reflecting |
| 207 |
> |
geometry, but may increase the photon distribution time. |
| 208 |
> |
.IP |
| 209 |
> |
\fBWARNING: this is an optimisation option for advanced users (an elite |
| 210 |
> |
group collectively known as \fIZe Ekspertz\fB) and may yield biased results. |
| 211 |
> |
Use with caution!\fR |
| 212 |
|
|
| 213 |
+ |
.IP "\fB\-lr \fImaxbounce\fR" |
| 214 |
+ |
Limit number of bounces (scattering events) along a photon path to |
| 215 |
+ |
\fImaxbounce\fR before being considered "runaway" and terminated. Photons |
| 216 |
+ |
paths are normally terminated via \fIRussian Roulette\fR, depending on their |
| 217 |
+ |
albedo. With unrealistically high albedos, this is not guaranteed, and this |
| 218 |
+ |
option imposes a hard limit to avoid an infinite loop. |
| 219 |
+ |
.IP |
| 220 |
+ |
\fBWARNING: this is an optimisation option for advanced users (an elite |
| 221 |
+ |
group collectively known as \fIZe Ekspertz\fB) and may yield biased results. |
| 222 |
+ |
Use with caution!\fR |
| 223 |
+ |
|
| 224 |
|
.IP "\fB\-ma \fIralb galb balb\fR" |
| 225 |
|
Set the global scattering albedo for participating media in conjunction |
| 226 |
|
with the \fB\-apv\fR option. See \fIrpict(1)\fR for details. |
| 233 |
|
Set the global scattering eccentricity for participating media in conjunction |
| 234 |
|
with the \fB\-apv\fR option. See \fIrpict(1)\fR for details. |
| 235 |
|
|
| 236 |
+ |
.IP "\fB\-n \fInproc\fR" |
| 237 |
+ |
Use \fInproc\fR processes for parallel photon distribution. There is no |
| 238 |
+ |
benefit in specifying more than the number of physical CPU cores available. |
| 239 |
+ |
This option is currently not available on Windows. |
| 240 |
+ |
|
| 241 |
|
.IP "\fB\-t \fIinterval\fR" |
| 242 |
|
Output a progress report every \fIinterval\fR seconds. This includes |
| 243 |
|
statistics about the currently emitting light source (including number of |
| 283 |
|
disabled with the photon map, as the resulting caustics are already accounted |
| 284 |
|
for. |
| 285 |
|
|
| 286 |
< |
.SS Dummy Sensor Surfaces |
| 286 |
> |
.SS Virtual Receiver Surfaces |
| 287 |
|
Since photons are surface bound, the density estimate is only asymptotically |
| 288 |
|
correct when performed at points which lie on the scene geometry. The |
| 289 |
|
irradiance is underestimated for arbitrarily placed points when photons are |
| 290 |
|
collected from distant surfaces. \fIMkpmap\fR offers a workaround with a |
| 291 |
< |
dummy sensor surface using the \fIantimatter\fR material; see the \fB-aps\fR |
| 291 |
> |
virtual receiver surface using the \fIantimatter\fR material; see the \fB-aps\fR |
| 292 |
|
and \fB-apS\fR options for details. |
| 293 |
|
|
| 294 |
|
.SH EXAMPLES |
| 312 |
|
Generate a contribution photon map containing 200000 photons suitable for |
| 313 |
|
obtaining light source contributions with \fIrcontrib(1)\fR: |
| 314 |
|
.IP |
| 315 |
< |
mkpmap \-apl bonzo-contrib.gpm 200k bonzo.oct |
| 315 |
> |
mkpmap \-apC bonzo-contrib.gpm 200k bonzo.oct |
| 316 |
|
|
| 317 |
|
.SH BUGS |
| 318 |
|
The focus of a spotlight source, as defined by the length of its direction |
| 335 |
|
(SNF). |
| 336 |
|
|
| 337 |
|
.SH "SEE ALSO" |
| 338 |
< |
rpict(1), rtrace(1), rvu(1), rcontrib(1), |
| 339 |
< |
\fIThe RADIANCE Photon Map Manual\fR |
| 340 |
< |
|
| 338 |
> |
rpict(1), rtrace(1), rvu(1), rcontrib(1), \fIThe RADIANCE Photon Map |
| 339 |
> |
Manual\fR, \fIDevelopment and Integration of the RADIANCE Photon Map |
| 340 |
> |
Extension: Technical Report\fR |
