stardis

Perform coupled heat transfer calculations
git clone git://git.meso-star.fr/stardis.git
Log | Files | Refs | README | LICENSE

stardis.1.in (22914B)


      1 .\" Copyright (C) 2018-2025 |Méso|Star> (contact@meso-star.com)
      2 .\"
      3 .\" This program is free software: you can redistribute it and/or modify
      4 .\" it under the terms of the GNU General Public License as published by
      5 .\" the Free Software Foundation, either version 3 of the License, or
      6 .\" (at your option) any later version.
      7 .\"
      8 .\" This program is distributed in the hope that it will be useful,
      9 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
     10 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
     11 .\" GNU General Public License for more details.
     12 .\"
     13 .\" You should have received a copy of the GNU General Public License
     14 .\" along with this program. If not, see <http://www.gnu.org/licenses/>.
     15 .Dd July 18, 2024
     16 .Dt STARDIS 1
     17 .Os
     18 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
     19 .Sh NAME
     20 .Nm stardis
     21 .Nd statistical solving of coupled thermal systems
     22 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
     23 .Sh SYNOPSIS
     24 .Nm
     25 .Op Fl eghiv
     26 .Op Fl a Ar diff_algo
     27 .Op Fl D Ar path_type , Ns Ar files_name_prefix
     28 .Op Fl d Ar file_base_name
     29 .Op Fl F Pa surface Ns Op , Ns Ar time Ns Op , Ns Ar time
     30 .Op Fl f Ar x , Ns Ar y , Ns Ar z Ns Op , Ns Ar time Ns Op , Ns Ar time
     31 .Op Fl G Pa green_bin Ns Op , Ns Pa green_ascii
     32 .Op Fl I Ar initial_time
     33 .Op Fl L Pa interface_probes
     34 .Op Fl l Pa interface_probes
     35 .Op Fl m Ar medium_name Ns Op , Ns Ar time Ns Op , Ns Ar time
     36 .Op Fl n Ar samples_count
     37 .Op Fl o Ar picard_order
     38 .Op Fl P Ar x , Ns Ar y , Ns Ar z Ns Oo , Ns Ar time Ns Oo , Ns Ar time Oc Oc \
     39  Ns Op : Ns Ar side_indicator
     40 .Op Fl p Ar x , Ns Ar y , Ns Ar z Ns Op , Ns Ar time Ns Op , Ns Ar time
     41 .Op Fl R Ar rendering_opt Ns Op : Ns Ar rendering_opt No ...
     42 .Op Fl S Pa surface Ns Op , Ns Ar time Ns Op , Ns Ar time
     43 .Op Fl s Pa surface Ns Op , Ns Ar time Ns Op , Ns Ar time
     44 .Op Fl t Ar threads_count
     45 .Op Fl V Ar verbosity_level
     46 .Op Fl X Pa output_rng
     47 .Op Fl x Pa input_rng
     48 .Fl M Pa system
     49 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
     50 .Sh DESCRIPTION
     51 .Nm
     52 solves coupled thermal systems: conductive, convective and radiative transfers
     53 are solved together.
     54 The physical model used for conduction is the local unstationary heat conduction
     55 equation.
     56 Convection fluxes are assumed to be linear with temperature, and radiation
     57 is assumed to be integrated over the whole thermal spectral range,
     58 therefore radiative heat fluxes are proportionnal to a difference of
     59 temperatures to the power 4.
     60 .Nm
     61 can deal with complex geometries as well as high-frequency external
     62 solicitations over a very long period of time, relative to the characteristic
     63 time of the system.
     64 The provided system description should comply with the
     65 .Xr stardis-input 5
     66 format.
     67 .Pp
     68 .Nm
     69 can compute a thermal observable, like temperature or flux, at a probe point and
     70 date or the mean value of an observable over a given surface, volume, or time
     71 range.
     72 When a time range
     73 .Ar t1 , Ns Ar t2
     74 is provided, the computed value is the mean value over the time range.
     75 To compute the value at a given time, simply provide a single value
     76 .Ar t .
     77 In addition,
     78 .Nm
     79 gives access to the evaluation of the propagator (a.k.a the Green function).
     80 The propagator is of great value for thermicist engineers as it gives some
     81 crucial information to analyse heat transfers in the system.
     82 It helps engineers answer questions like
     83 .Dq Where from does the heat come at this location? .
     84 Propagators seamlessly aggregate all the provided geometrical and physical
     85 information on the system in an unbiased and very-fast statistical model.
     86 .Pp
     87 .Nm
     88 also provides two additional functionalities: converting the
     89 .Xr stardis-input 5
     90 geometry into a VTK file and rendering an infrared image of
     91 the submitted system.
     92 .Pp
     93 .Nm Ns '
     94 algorithms are based on state-of-the-art Monte Carlo method applied to radiative
     95 transfer physics (Delatorre et al. 2014) combined with conduction's
     96 statistical formulation (Kac 1949 and Muller 1956).
     97 Monte Carlo algorithms associated with convective and conductive processes
     98 consist in sampling heat paths: this can be seen as an extension of Monte Carlo
     99 algorithms that solve monochromatic radiative transfer.
    100 The radiative transfer algorithm, based on the Picard method, is also based on
    101 sampling radiative paths.
    102 However, since
    103 .Nm
    104 solves the spectrally integrated radiative transfer, the process can be
    105 recursive: secondary heat paths (convective, conductive and radiative) may be
    106 necessary along the sampling of an initial radiative path.
    107 The solution may not be sufficiently converged with a Picard order equal to 1 in
    108 the presence of high temperature gradients.
    109 Increasing the Picard order may be necessary in this case, until the required
    110 convergence is reached.
    111 .Pp
    112 One of the key features of
    113 .Nm
    114 is that its algorithms are not based on a volumetric mesh of the system:
    115 only the representation of its interfaces is required.
    116 And these are used only as a description of the system, not as a basis
    117 for calculation, whose discretization would have an impact on the
    118 accuracy of estimates.
    119 .Pp
    120 .Nm
    121 implements mixed parallelism.
    122 On a single computer (that is, a node), it uses shared memory parallelism while
    123 it relies on Message Passing Interface (MPI) to parallelize calculations between
    124 multiple nodes.
    125 .Nm
    126 can therefore be launched either directly or via a process launcher such as
    127 .Xr mpirun 1
    128 to distribute the calculation on several computers.
    129 .Pp
    130 The options are as follows:
    131 .Bl -tag -width Ds
    132 .It Fl a Ar diff_algo
    133 Define the diffusion algorithm to be used when sampling a conductive
    134 path.
    135 The default diffusion algorithm is
    136 .Cm dsphere .
    137 .Pp
    138 The diffusion algorithms are as follows:
    139 .Bl -tag -width Ds
    140 .It Cm dsphere
    141 Use the delta sphere algorithm, in which Brownian motion is approximated
    142 by a random walk of random delta steps.
    143 The algorithm is consistent with respect to the
    144 .Ar delta
    145 parameter, i.e. Brownian motion is estimated exactly with
    146 .Ar delta
    147 tending towards 0.
    148 This numerical parameter
    149 .Ar delta
    150 is defined by solid and can be varied in
    151 time and space to handle the spatio-temporal temperature gradient
    152 without prohibitively increasing computation time
    153 .Pq see Xr stardis-input 1 .
    154 .It Cm wos
    155 Use the Walk on Sphere algorithm to estimate Brownian motion.
    156 Although a numerical parameter is required to define the distance at
    157 which the random walk is considered to have reached the boundary, it can
    158 be assumed that this algorithm estimates Brownian motion without any
    159 bias with respect to numerical uncertainty.
    160 Indeed, the aforementioned distance can be set to the computer's
    161 numerical accuracy without any significant impact on performance.
    162 .El
    163 .It Fl D Ar path_type , Ns Ar files_name_prefix
    164 Write sampled heat paths of the given
    165 .Ar path_type
    166 to files in VTK format, one file per path.
    167 Possible values for
    168 .Ar path_type
    169 are
    170 .Cm error
    171 .Pq write paths ending in error ,
    172 .Cm success
    173 .Pq write successful paths ,
    174 and
    175 .Cm all
    176 .Pq write all paths .
    177 Actual file names are produced by appending
    178 .Ar files_name_prefix
    179 and the path rank starting at index
    180 .Ql 00000000 ,
    181 and possibly followed by
    182 .Ql _err
    183 for failure paths
    184 .Pq e.g. Pa prefix00000000.vtk , Pa prefix00000001_err.vtk
    185 .Pp
    186 Can only be used in conjunction with some options that sample heat paths
    187 .Pq Fl m , Fl p , Fl P , Fl R, Fl s No or Fl S .
    188 .It Fl d Ar file_base_name
    189 Write the geometry to a file in VTK format along with various properties,
    190 including possible errors.
    191 Also possibly write some problematic parts of the geometry (if any) in OBJ
    192 format.
    193 Possible parts are overlapping triangles, riangles with property conflicts, and
    194 triangles with merge errors.
    195 The various file are all named after the provided base name.
    196 If this option is used, no computation occurs.
    197 .Pp
    198 Using this option in conjunction with an option that
    199 specifies a compute region
    200 .Pq i.e. Fl F , Fl S ,  Fl s
    201 has the effect to include the region in the VTK output.
    202 .It Fl e
    203 Use extended format to output Monte Carlo results.
    204 Can only be used in conjunction with options that compute a single Monte-Carlo
    205 .Pq Fl F , Fl m , Fl P , Fl p No or Fl s No without options Fl g No or Fl G .
    206 .It Fl F Pa surface Ns Op , Ns Ar time Ns Op , Ns Ar time
    207 Compute the flux through a given 2D surface at a given time, the surface being
    208 defined by the triangles in a STL file.
    209 The flux can only be computed on a solid-fluid interface and is accounted
    210 positive from the solid to the fluid.
    211 These triangles are not added to the geometry, but must be part of it.
    212 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    213 The surface does not need to be connex.
    214 .It Fl f Ar x , Ns Ar y , Ns Ar z Ns Op , Ns Ar time Ns Op , Ns Ar time
    215 Compute the flux density at a given probe on an interface at a given time.
    216 The probe is supposed to be on an interface and is moved to the closest point of
    217 the closest interface before the computation starts.
    218 The flux density can only be computed on a solid-fluid interface and is
    219 accounted positive from the solid to the fluid.
    220 The probe coordinates must be in the same system as the geometry.
    221 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    222 .It Fl G Pa green_bin Ns Op , Ns Pa green_ascii
    223 Compute the Green function at the specified time and write it to a binary file.
    224 If a
    225 .Pa green_ascii
    226 file name is provided, information on heat paths' ends is also written in this
    227 second file in ascii csv format.
    228 .Pp
    229 This option can only be used in conjunction with one these options:
    230 .Fl p , Fl P , Fl m , Fl s
    231 and cannot be used in conjunction with option
    232 .Fl D .
    233 .Pp
    234 The resulting file can be further used through the
    235 .Xr sgreen 1
    236 command to apply different temperature, flux or volumic power values.
    237 .It Fl g
    238 Compute the Green function at the specified time and write it in ASCII to
    239 standard output.
    240 This option can only be used in conjunction with one these options:
    241 .Fl p , Fl P , Fl m , Fl s
    242 and cannot be used in conjunction with option
    243 .Fl D .
    244 .It Fl h
    245 Output short help and exit.
    246 .It Fl I Ar initial_time
    247 Define initial time in seconds.
    248 It can take any value between +/- infinity.
    249 The default initial time is 0.
    250 .It Fl i
    251 Disable internal radiative exchanges.
    252 External radiative exchanges are still processed, i.e. the external
    253 source.
    254 .It Fl L Pa interface_probes
    255 Defines a set of interface probes for which
    256 .Nm
    257 calculates the temperature.
    258 The argument file lists the interface probe points.
    259 Each line of this file describes a probe point using the same grammar as
    260 that used to describe a single interface probe
    261 .Pq see Fl P No option .
    262 In addition to this syntax, characters behind the hash mark
    263 .Pq Ql #
    264 are considered comments and are therefore ignored, as are empty lines,
    265 i.e. lines with no characters at all or composed solely of spaces and
    266 tabs.
    267 .Pp
    268 Note that this option parallelizes the calculation of the probe list,
    269 and not the calculation of each individual probe.
    270 Its use is therefore more advantageous in terms of load distribution
    271 when the number of probes to be evaluated is large, compared with the
    272 cost of calculating a single probe point.
    273 .It Fl l Pa interface_probes
    274 Defines a set of interface probes for which
    275 .Nm
    276 calculates the flux density.
    277 The argument file lists the interface probe points.
    278 Each line of this file describes a probe point using the same grammar as
    279 that used to describe a single interface probe
    280 .Pq see Fl f No option .
    281 In addition to this syntax, characters behind the hash mark
    282 .Pq Ql #
    283 are considered comments and are therefore ignored, as are empty lines,
    284 i.e. lines with no characters at all or composed solely of spaces and
    285 tabs.
    286 .Pp
    287 This option allows the calculation of the probe list while reading and
    288 constructing the system only once.
    289 .It Fl M Pa system
    290 Read a text file containing a possibly partial description of the system.
    291 Can include programs, media enclosures and boundary conditions.
    292 Media and boundaries can appear in any order, but programs must be defined
    293 before their first reference.
    294 Refer to
    295 .Xr stardis-input 5
    296 for a full description of the file format.
    297 Can be used more than once if the description is split across different files.
    298 .It Fl m Ar medium_name Ns Op , Ns Ar time Ns Op , Ns Ar time
    299 Compute the mean temperature in a given medium at a given time.
    300 The medium name must be part of the
    301 .Pa system
    302 description.
    303 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    304 The medium region does not need to be connex.
    305 .It Fl n Ar samples_count
    306 Number of Monte Carlo realisations.
    307 By default, the number of realisations is
    308 @STARDIS_ARGS_DEFAULT_SAMPLES_COUNT@.
    309 .It Fl o Ar picard_order
    310 Determine the iteration level used with the Picard method to deal with
    311 non-linear radiative transfer accross the model.
    312 By default
    313 .Ar picard_order
    314 is set to @STARDIS_ARGS_DEFAULT_PICARD_ORDER@.
    315 Note that a Picard order greater than 1 is incompatible both with Green
    316 computations and systems including volumic power sources or non zero flux at a
    317 boundary.
    318 .It Fl P Ar x , Ns Ar y , Ns Ar z Ns Oo , Ns Ar time Ns Oo , Ns Ar time Oc Oc \
    319 Ns Op : Ns Ar side_indicator
    320 Compute the temperature at the given probe on an interface at a given time.
    321 If the probe is on an interface where a thermal contact resistance is defined,
    322 it is mandatory to provide a side indicator
    323 .Pq either Cm FRONT , Cm BACK , No or a medium name ,
    324 as the temperature differs between the two sides.
    325 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    326 The probe is supposed to be on an interface and is moved to the closest point of
    327 the closest interface before the computation starts.
    328 The probe coordinates must be in the same system as the geometry.
    329 .It Fl p Ar x , Ns Ar y , Ns Ar z Ns Op , Ns Ar time Ns Op , Ns Ar time
    330 Compute the temperature at the given probe at a given time.
    331 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    332 The probe must be in a medium.
    333 The probe coordinates must be in the same system as the geometry.
    334 .It Fl R Ar rendering_opt Ns Op : Ns Ar rendering_opt No ...
    335 Render an infrared image of the system through a pinhole camera.
    336 One can use all-default sub-options by simply providing the colon character
    337 .Pq Ql \&:
    338 alone as an argument.
    339 Please note that the camera position must be outside the geometry or in a fluid.
    340 .Pp
    341 The rendering options are as follows:
    342 .Bl -tag -width Ds
    343 .It Cm file= Ns Pa output_file
    344 File name to use to write the infrared image to.
    345 If no file name is provided, the result is written to standard output.
    346 .It Cm fmt= Ns Ar image_file_format
    347 Format of the image file in output.
    348 Can be
    349 .Cm VTK ,
    350 or
    351 .Cm HT
    352 .Pq see Xr htrdr-image 5 No and Xr htpp 1 .
    353 Default
    354 .Ar image_file_format
    355 is @STARDIS_ARGS_DEFAULT_RENDERING_OUTPUT_FILE_FMT@.
    356 .It Cm fov= Ns Ar angle
    357 Vertical field of view of the camera in [30,120] degrees.
    358 The default field of view is @STARDIS_ARGS_DEFAULT_RENDERING_FOV@ degrees.
    359 .It Cm img= Ns Ar width Ns x Ns Ar height
    360 Image definition.
    361 Default is
    362 @STARDIS_ARGS_DEFAULT_RENDERING_IMG_WIDTH@x@STARDIS_ARGS_DEFAULT_RENDERING_IMG_HEIGHT@.
    363 .It Cm pos= Ns Ar x , Ns Ar y , Ns Ar z
    364 Camera position.
    365 Default is @STARDIS_ARGS_DEFAULT_RENDERING_POS@ unless
    366 .Cm tgt
    367 is not defined, in which case the position is automatically calculated to ensure
    368 that the entire scene is visible.
    369 .It Cm spp= Ns Ar samples_per_pixel
    370 Number of samples to solve the Monte Carlo estimation of each pixel.
    371 Default is @STARDIS_ARGS_DEFAULT_RENDERING_SPP@.
    372 .It Cm t= Ns Ar time , Ns Op Ns Ar time
    373 Rendering time.
    374 Default is @STARDIS_ARGS_DEFAULT_RENDERING_TIME@.
    375 .It Cm tgt= Ns Ar x , Ns Ar y , Ns Ar z
    376 Targeted position.
    377 Default is @STARDIS_ARGS_DEFAULT_RENDERING_TGT@ unless
    378 .Cm pos
    379 is not defined, in which case the targeted position is automatically calculated
    380 to ensure that the entire scene is visible.
    381 .It Cm up= Ns Ar x , Ns Ar y , Ns Ar z
    382 Upward vector that the top of the camera is pointing towards.
    383 Default is @STARDIS_ARGS_DEFAULT_RENDERING_UP@.
    384 .El
    385 .It Fl S Pa surface Ns Op , Ns Ar time Ns Op , Ns Ar time
    386 Compute the by-triangle mean temperature on a given 2D
    387 .Pa surface
    388 at a given time,
    389 the
    390 .Pa surface
    391 defined as the front sides of the triangles in the provided STL file.
    392 These triangles are not added to the geometry, but must be part of it.
    393 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    394 The
    395 .Pa surface
    396 does not need to be connex.
    397 .It Fl s Pa surface Ns Op , Ns Ar time Ns Op , Ns Ar time
    398 Compute the mean temperature on a given 2D
    399 .Pa surface
    400 at a given time, the
    401 .Pa surface
    402 being defined as the front sides of the triangles in the provided STL file.
    403 By default the compute time is @STARDIS_ARGS_DEFAULT_COMPUTE_TIME@.
    404 These triangles are not added to the geometry, but must be part of it.
    405 The
    406 .Pa surface
    407 does not need to be connex.
    408 .It Fl t Ar threads_count
    409 Advice on the number of threads to use.
    410 By default,
    411 .Nm
    412 uses many threads as processor cores.
    413 .It Fl V Ar verbosity_level
    414 Set the verbosity level.
    415 Possible values are
    416 .Ql 0
    417 .Pq no message ,
    418 .Ql 1
    419 .Pq error messages only ,
    420 .Ql 2
    421 .Pq error and warning messages ,
    422 and
    423 .Ql 3
    424 .Pq error, warning and informative messages .
    425 All the messages are written to standard error.
    426 Default is @STARDIS_ARGS_DEFAULT_VERBOSE_LEVEL@.
    427 .It Fl v
    428 Output version information and exit.
    429 .It Fl X Pa output_rng
    430 Write the random generator's internal state, as it is at the end of the
    431 computation, to the provided file.
    432 .It Fl x Pa input_rng
    433 Read the provided file and use its content to initialize the random generator's
    434 internal state.
    435 Used in conjunction with the
    436 .Fl X
    437 option, this can be used to ensure statistical independence between subsequent
    438 computations.
    439 .El
    440 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    441 .Sh EXIT STATUS
    442 .Ex -std
    443 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    444 .Sh EXAMPLES
    445 Preprocess the system as described in
    446 .Pa scene 5.txt
    447 when intending to compute the mean flux on the triangles from the file
    448 .Pa edge.stl ,
    449 and write its geometry in the file
    450 .Pa scene.vtk .
    451 Verbosity level is set to
    452 .Ar 3 :
    453 .Bd -literal -offset Ds
    454 stardis -M "scene 5.txt" -F edge.stl -d -V 3 > scene.vtk
    455 .Ed
    456 .Pp
    457 Compute the temperature at the probe point
    458 .Ar 0 , Ns Ar 0.5 , Ns Ar 0
    459 at steady state.
    460 The system is read from the file
    461 .Pa model.txt
    462 and the number of samples is set to
    463 .Ar 1000000 :
    464 .Bd -literal -offset Ds
    465  stardis -M model.txt -p 0,0.5,0 -n 1000000
    466 .Ed
    467 .Pp
    468 Compute the mean temperature in the medium
    469 .Ar med05
    470 at
    471 .No t= Ns Ar 100 Ns s .
    472 The system is read from the file
    473 .Pa model.txt
    474 and the result is output with extended format
    475 .Pq option Fl e :
    476 .Bd -literal -offset Ds
    477 stardis -M model.txt -m med05,100 -e
    478 .Ed
    479 .Pp
    480 Compute the temperature at the probe point
    481 .Ar 0 , Ns Ar 0 , Ns Ar 0
    482 at
    483 .No t= Ns Ar 2500 .
    484 The system is read from the 2 files
    485 .Pa media.txt
    486 and
    487 .Pa bounds.txt ,
    488 and the number of samples is set to
    489 .Ar 1000000 :
    490 .Bd -literal -offset Ds
    491 stardis -M media.txt -M bounds.txt -p 0,0,0,2500 -n 1000000
    492 .Ed
    493 .Pp
    494 Compute the mean temperature at the probe point
    495 .Ar 1 , Ns Ar 2.5 , Ns Ar 0
    496 over the
    497 .Ar 50 , Ns Ar 5000
    498 time range.
    499 The system is read from the file
    500 .Pa model.txt :
    501 .Bd -literal -offset Ds
    502 stardis -M model.txt -p 1,2.5,0,50,5000
    503 .Ed
    504 .Pp
    505 Compute 3 probe temperatures, ensuring statistical independence:
    506 .Bd -literal -offset Ds
    507 stardis -M model.txt -p 1,1.5,0,50,5000 -Xstate1
    508 stardis -M model.txt -p 1,2.5,0,50,5000 -xstate1 -Xstate2
    509 stardis -M model.txt -p 1,3.5,0,50,5000 -xstate2
    510 .Ed
    511 .Pp
    512 Use
    513 .Xr mpirun 1
    514 to launch
    515 .Nm
    516 on several hosts defined in the my_hosts file.
    517 Render the system as described in
    518 .Pa scene.txt
    519 with default settings:
    520 .Bd -literal -offset Ds
    521 mpirun --hostfile my_hosts stardis -M scene.txt -R\&:
    522 .Ed
    523 .Pp
    524 Render the system as described in
    525 .Pa scn.txt
    526 at
    527 .Ar 100
    528 seconds
    529 Using 2 samples per pixel
    530 for an image of
    531 .Ar 800 No by Ar 600
    532 pixels
    533 saved in
    534 .Xr htrdr-image 5
    535 format
    536 and all other settings set to their default values.
    537 The output is redirected to the
    538 .Pa img.ht
    539 file.
    540 If the computation encounters erroneous heat paths, they will be dumped to VTK
    541 files named
    542 .Pa err_path_00000000.vtk , err_path_00000001.vtk ,
    543 etc.
    544 The image file is then post-processed using
    545 .Xr htpp 1
    546 with default settings to obtain a png file:
    547 .Bd -literal -offset Ds
    548 stardis -M scn.txt \\
    549         -R t=100:spp=2:img=800x600:fmt=ht \\
    550         -D error,err_path_ \\
    551         > img.ht
    552 htpp -o img.pgn -v -m default img.ht
    553 .Ed
    554 .Pp
    555 Compute the Green function that computes the temperature at the probe point
    556 .Ar 0 , Ns Ar 0 , Ns Ar 0
    557 at steady state.
    558 The system is read from the file
    559 .Pa model.txt
    560 and the Green function is written to the
    561 .Pa probe.green
    562 file and the heat paths' ends are written to the
    563 .Pa probe_ends.csv
    564 file:
    565 .Bd -literal -offset Ds
    566 stardis -M model.txt -p 0,0,0 -G probe.green,probe_ends.csv
    567 .Ed
    568 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    569 .Sh SEE ALSO
    570 .Xr htpp 1 ,
    571 .Xr mpirun 1 ,
    572 .Xr sgreen 1 ,
    573 .Xr htrdr-image 5 ,
    574 .Xr stardis-input 5 ,
    575 .Xr stardis-output 5
    576 .Rs
    577 .%A Léa Penazzi et al.
    578 .%T Path integrals formulations leading to propagator evaluation for coupled \
    579 linear physics in large geometric models
    580 .%J Computer Physics Communications
    581 .%V 294
    582 .%D 2024
    583 .%U https://doi.org/10.1016/j.cpc.2023.108911
    584 .Re
    585 .Rs
    586 .%A Mégane Bati et al.
    587 .%T Coupling Conduction, Convection and Radiative Transfer in a Single \
    588 Path-Space: Application to Infrared Rendering
    589 .%J ACM Transactions on Graphics
    590 .%V 42
    591 .%N 4
    592 .%D August 2023
    593 .%U https://doi.org/10.1145/3592121
    594 .Re
    595 .Rs
    596 .%A Jean Marc Tregan et al.
    597 .%T Coupling radiative, conductive and convective heat-transfers in a single \
    598 Monte Carlo algorithm: A general theoretical framework for linear situations
    599 .%J PLOS ONE
    600 .%V 18
    601 .%N 4
    602 .%D 2023
    603 .%U https://doi.org/10.1371/journal.pone.0283681
    604 .Re
    605 .Rs
    606 .%A Jérémie Delatorre et al.
    607 .%T Monte Carlo advances and concentrated solar applications
    608 .%J Solar Energy
    609 .%V 103
    610 .%P 653--681
    611 .%D 2014
    612 .%U https://doi.org/10.1016/j.solener.2013.02.035
    613 .Re
    614 .Rs
    615 .%A Abdolhossein Haji-Sheikh
    616 .%A Ephraim Maurice Sparrow
    617 .%T The floating random walk and its applications to Monte-Carlo \
    618 solutions of heat equations
    619 .%J SIAM Journal on Applied Mathematics
    620 .%V 14
    621 .%N 2
    622 .%P 370--389
    623 .%D 1966
    624 .Re
    625 .Rs
    626 .%A Mervin E Muller
    627 .%T Some continuous Monte Carlo methods for the Dirichlet problem
    628 .%J The Annals of Mathematical Statistics
    629 .%P 569--589
    630 .%D 1956
    631 .Re
    632 .Rs
    633 .%A Mark Kac
    634 .%T On distributions of certain Wiener functionals
    635 .%J Transactions of the American Mathematical Society
    636 .%V 65
    637 .%N 1
    638 .%P 1--13
    639 .%D 1949
    640 .Re
    641 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    642 .Sh STANDARDS
    643 .Rs
    644 .%B The VTK User's Guide
    645 .%O Simple Legacy Formats
    646 .%I Kitware, Inc
    647 .%N 11
    648 .%D 2010
    649 .%P 470--482
    650 .Re
    651 .Pp
    652 .Rs
    653 .%A OpenMP Architecture Review Board
    654 .%D March 2002
    655 .%T OpenMP C and C++ Application Interface
    656 .%O version 2.0
    657 .Re
    658 .Pp
    659 .Rs
    660 .%A Message Passing Interface Forum
    661 .%D July 1997
    662 .%T MPI-2: Extensions to The Message-Passing Interface
    663 .Re
    664 .Pp
    665 .Rs
    666 .%T The StL Format: Standard Data Format for Fabbers
    667 .%A Marshall Burns
    668 .%D 1993
    669 .%U https://www.fabbers.com/tech/STL_Format
    670 .Re