htrdr-atmosphere.1.in (23696B)
1 .\" Copyright (C) 2018-2019, 2022-2025 Centre National de la Recherche Scientifique 2 .\" Copyright (C) 2020-2022 Institut Mines Télécom Albi-Carmaux 3 .\" Copyright (C) 2022-2025 Institut Pierre-Simon Laplace 4 .\" Copyright (C) 2022-2025 Institut de Physique du Globe de Paris 5 .\" Copyright (C) 2018-2025 |Méso|Star> (contact@meso-star.com) 6 .\" Copyright (C) 2022-2025 Observatoire de Paris 7 .\" Copyright (C) 2022-2025 Université de Reims Champagne-Ardenne 8 .\" Copyright (C) 2022-2025 Université de Versaille Saint-Quentin 9 .\" Copyright (C) 2018-2019, 2022-2025 Université Paul Sabatier 10 .\" 11 .\" This program is free software: you can redistribute it and/or modify 12 .\" it under the terms of the GNU General Public License as published by 13 .\" the Free Software Foundation, either version 3 of the License, or 14 .\" (at your option) any later version. 15 .\" 16 .\" This program is distributed in the hope that it will be useful, 17 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of 18 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 .\" GNU General Public License for more details. 20 .\" 21 .\" You should have received a copy of the GNU General Public License 22 .\" along with this program. If not, see <http://www.gnu.org/licenses/>. 23 .Dd January 24, 2024 24 .Dt HTRDR-ATMOSPHERE 1 25 .Os 26 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 27 .\" Name and Short description 28 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 29 .Sh NAME 30 .Nm htrdr-atmosphere 31 .Nd simulate radiative transfer in cloudy atmospheres 32 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 33 .\" Summary of options 34 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 35 .Sh SYNOPSIS 36 .Nm 37 .Op Fl dfhRrv 38 .Op Fl c Pa clouds 39 .Op Fl C Ar persp_camera_opt Ns Op : Ns Ar persp_camera_opt No ... 40 .Op Fl D Ar sun_azimuth , Ns Ar sun_elevation 41 .Op Fl g Pa ground 42 .Op Fl i Ar image_opt Ns Op : Ns Ar image_opt No ... 43 .Op Fl M Pa materials 44 .Op Fl m Pa mie 45 .Op Fl n Ar sky_mtl 46 .Op Fl O Pa cache 47 .Op Fl o Pa output 48 .Op Fl P Ar ortho_camera_opt Ns Op : Ns Ar ortho_camera_opt No ... 49 .Op Fl p Ar flux_sensor_opt Ns Op : Ns Ar flux_sensor_opt No ... 50 .Op Fl s Ar spectral_opt Ns Op : Ns Ar spectral_opt No ... 51 .Op Fl T Ar optical_thickness 52 .Op Fl t Ar threads_count 53 .Op Fl V Ar x , Ns Ar y , Ns Ar z 54 .Fl a Pa atmosphere 55 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 56 .\" Detailed description 57 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 58 .Sh DESCRIPTION 59 .Nm 60 simulates radiative transfer in scenes composed of an atmospheric gas 61 mixture, liquid clouds, and a ground. 62 It evaluates the intensity incoming on each pixel of the sensor array. 63 The underlying algorithm is based on a Monte Carlo method: it consists 64 in simulating a given number of optical paths originating from the 65 sensor, directed into the atmosphere, taking into account light 66 absorption and scattering phenomena. 67 .Pp 68 Radiative transfer can be evaluated in any part of the spectrum. 69 It uses the k distributions to be provided for the vertical profile of 70 atmospheric pressure and temperature 71 .Pq option Fl a . 72 For clouds, the user must define the liquid water content suspended in 73 clouds 74 .Pq option Fl c , 75 and the optical properties of water droplets 76 .Pq option Fl m . 77 All that remains is to define the position of the sun 78 .Pq option Fl D , 79 the properties of the sensor 80 .Pq options Fl C , Fl P No or Fl p 81 and the definition of the image 82 .Pq option Fl i . 83 You can also enter the geometry of the ground 84 .Pq option Fl g 85 and its associated materials 86 .Pq option Fl M . 87 Note that clouds and ground can be infinitely repeated along the X and Y 88 axis 89 .Pq option Fl r No and Fl R . 90 .Pp 91 Four types of sensor are provided. 92 The pinhole camera and the thin-lens camera 93 .Pq option Fl C 94 are used to calculate the image of the scene from a given viewpoint. 95 Unlike these two cameras, the orthographic camera 96 .Pq option Fl P 97 uses parallel projection rather than perspective projection. 98 Finally, the rectangular sensor 99 .Pq option Fl p 100 is used to calculate flux maps. 101 .Pp 102 The spectral dimension can be integrated in various ways 103 .Pq option Fl s . 104 When rendering an image 105 .Pq options Fl C No and Fl P 106 the calculation is by default performed for the visible part of the 107 spectrum between 108 .Bq 380, 780 109 nanometers, for the three components of the CIE 1931 XYZ color space 110 which are then recombined to obtain the final color for each pixel. 111 The other method consists of explicitly defining the longwave or 112 shortwave spectral range to be processed and continuously sampling a 113 wavelength within this range. 114 Longwave and shortwave are key words here meaning that the source of 115 radiation is either internal or external to the medium. 116 For short-wave images the radiance of the pixel is evaluated and stored 117 at the output. 118 For long-wave images this estimated radiance is then converted into 119 brightness temperature and both are stored at the output. 120 When calculating a flux map 121 .Pq option Fl p 122 the flux per pixel is stored in the output map regardless of whether the 123 spectral range is longwave or shortwave. 124 .Pp 125 In 126 .Nm 127 the spatial unit 1.0 corresponds to one meter and temperatures are 128 expressed in Kelvin. 129 Estimated radiances are given in W/sr/m^2 except for monochromatic 130 calculations where the calculated spectral radiance is defined in 131 W/sr/m^2/nm. 132 Flux densities are recorded in W/m^2. 133 The results are written to the output file if the 134 .Fl o 135 option is set and otherwise to standard output. 136 The output image is a list of raw ASCII data formatted using the 137 .Xr htrdr-image 5 138 file format. 139 .Pp 140 .Nm 141 implements mixed parallelism. 142 On a single computer (that is, a node), it uses shared memory 143 parallelism while it relies on Message Passing Interface (MPI) to 144 parallelize calculations between multiple nodes. 145 .Nm 146 can therefore be launched either directly or via a process launcher such 147 as 148 .Xr mpirun 1 149 to distribute the calculation on several computers. 150 .Pp 151 The options are as follows: 152 .Bl -tag -width Ds 153 .It Fl a Ar atmosphere 154 Optical properties of atmospheric gases saved in htgop format. 155 .It Fl c Pa clouds 156 Cloud properties saved in 157 .Xr htcp 5 158 format. 159 .It Fl C Ar persp_camera_opt Ns Op : Ns Ar persp_camera_opt No ... 160 Set up a pinhole or thin-lens perspective camera. 161 .Pp 162 The options for a perspective camera are as follows: 163 .Bl -tag -width Ds 164 .It Cm focal-dst= Ns Ar distance 165 Distance to focus on with a thin lens camera, that is, a camera whose 166 .Cm lens-radius 167 is not zero. 168 The default focal distance is 169 @HTRDR_ARGS_DEFAULT_CAMERA_PERSPECTIVE_FOCAL_DST@ meters. 170 .It Cm focal-length= Ns Ar length 171 Focal length of a camera lens. 172 It is another way to control the field of view of a thin lens camera. 173 By default, the field of view is set through the 174 .Cm fov 175 parameter. 176 .It Cm fov= Ns Ar angle 177 Vertical field of view of the camera in 178 ]@HTRDR_ARGS_CAMERA_PERSPECTIVE_FOV_EXCLUSIVE_MIN@, 179 @HTRDR_ARGS_CAMERA_PERSPECTIVE_FOV_EXCLUSIVE_MAX@[ degrees. 180 The default field of view is 181 @HTRDR_ARGS_DEFAULT_CAMERA_PERSPECTIVE_FOV@ degrees. 182 .It Cm lens-radius= Ar radius 183 Radius of the camera lens. 184 A non-zero radius means that the camera is a thin lens camera while a 185 zero radius defines a pinhole camera. 186 The default lens radius is 187 @HTRDR_ARGS_DEFAULT_CAMERA_PERSPECTIVE_LENS_RADIUS@. 188 .It Cm pos= Ns Ar x , Ns Ar y , Ns Ar z 189 Camera position. 190 Default is @HTRDR_ARGS_DEFAULT_CAMERA_POS@. 191 .It Cm tgt= Ns Ar x , Ns Ar y , Ns Ar z 192 Targeted position 193 Default is @HTRDR_ARGS_DEFAULT_CAMERA_TGT@. 194 .It Cm up= Ns Ar x , Ns Ar y , Ns Ar z 195 Upward vector that the top of the camera is pointing towards. 196 Default is @HTRDR_ARGS_DEFAULT_CAMERA_UP@. 197 .El 198 .It Fl D Ar sun_azimuth , Ns Ar sun_elevation 199 Direction toward the sun center. 200 The direction is defined by two angles in degrees: 201 the 202 .Ar sun_azimuth 203 angle in [0, 360[ and the 204 .Ar sun_elevation 205 angle in [0, 90]. 206 .Pp 207 Following the right-handed convention, the azimuthal rotation is 208 counter-clockwise, with 0 degree on the X axis. 209 The elevation starts from 0 degree for a direction in the XY plane, up 210 to 90 degrees at zenith. 211 Thus 212 .Li -D\ 0,0 , 213 .Li -D\ 90,0 , 214 .Li -D\ 180,0 215 and 216 .Li -D\ 270,0 217 will produce solar vectors 218 .Pq +1,0,0 , 219 .Pq 0,+1,0 , 220 .Pq -1,0,0 221 and 222 .Pq 0,-1,0 223 respectively, while 224 .Li -D\ Ns Ar sun_azminuth , Ns 90 225 will produce 226 .Pq 0,0,+1 227 regardless of 228 .Ar sun_azimuth 229 value. 230 .It Fl d 231 Write to 232 .Pa output 233 the space partitioning data structures used to speed up cloud radiative 234 transfer calculations. 235 The data written are octrees saved in legacy VTK file format. 236 Each octree node stores the minimum and maximum extinction coefficients 237 of the cloud cells covered by the octree node. 238 In the output file, each octree is separated from the previous one 239 by a line containing three minus characters, i.e.\& 240 .Li --- . 241 .It Fl f 242 Force overwriting of 243 .Pa output 244 file. 245 .It Fl g Pa ground 246 Ground geometry saved in 247 .Xr htrdr-obj 5 248 format. 249 .It Fl h 250 Display short help and exit. 251 .It Fl i Ar image_opt Ns Op : Ns Ar image_opt No ... 252 Configure sensor image. 253 .Pp 254 The image options are as follows: 255 .Bl -tag -width Ds 256 .It Cm def= Ns Ar width Ns x Ns Ar height 257 Image definition. 258 Default is 259 @HTRDR_ARGS_DEFAULT_IMG_WIDTH@x@HTRDR_ARGS_DEFAULT_IMG_HEIGHT@. 260 .It Cm spp= Ns Ar samples_per_pixel 261 Number of samples to solve the Monte Carlo estimation of each pixel. 262 In normal image rendering, a pixel will be estimated with 263 .No 3\ *\ Ns Ar samples_per_pixel 264 of Monte Carlo realisations, one set of 265 .Ar samples_per_pixel 266 for each X, Y and Z component of the CIE 1931 XYZ color space. 267 In shortwave and longwave 268 rendering or flux calculation, only one set of 269 .Ar samples_per_pixel 270 is used. 271 By default, 272 .Cm spp 273 is set to @HTRDR_ARGS_DEFAULT_IMG_SPP@. 274 .El 275 .It Fl R 276 Repeat the ground along the X and Y axes to infinity. 277 .It Fl r 278 Repeat the clouds along the X and Y axes to infinity. 279 .It Fl M Pa materials 280 Ground materials saved in 281 .Xr htrdr-materials 5 282 format. 283 .It Fl m Pa mie 284 Optical properties of water droplets saved in 285 .Xr htmie 5 286 format. 287 .It Fl n Ar sky_mtl 288 Name in the 289 .Pa materials 290 file representing the sky, i.e. the semi-transparent material. 291 Default is @HTRDR_ATMOSPHERE_ARGS_DEFAULT_SKY_MTL_NAME@. 292 .It Fl O Pa cache 293 File where atmospheric acceleration structures are stored/loaded. 294 If the 295 .Pa cache 296 file does not exist, it is created and filled with acceleration 297 structures constructed from the clouds 298 .Pq option Fl c , 299 atmosphere 300 .Pq option Fl a 301 and mie 302 .Pq option Fl m 303 input files. 304 This cached data can then be reused in subsequent executions, provided 305 that the input files supplied to the command are the same as those used 306 to set up the cache, thus considerably speeding up the pre-processing 307 stage. 308 .Pp 309 If 310 .Pa cache 311 contains data generated from input files that are not those submitted on 312 the command line, an error is notified and execution is aborted, thus 313 avoiding the use of bad cached data. 314 .Pp 315 Note that when the cache is used, 316 .Nm 317 ignores the options used to build acceleration structures 318 .Pq options Fl T No and Fl V . 319 .It Fl o Pa output 320 Output file. 321 If not defined, data is written to standard output. 322 .It Fl P Ar ortho_camera_opt Ns Op : Ns Ar ortho_camera_opt No ... 323 Set up an orthographic camera. 324 .Pp 325 The options for an orthographic camera are as follows: 326 .Bl -tag -width Ds 327 .It Cm height= Ns Ar lenght 328 Image plane height. 329 Its width is calculated from this length and the image ratio 330 to guarantee square pixels 331 .Pq see Fl i No option . 332 .It Cm pos= Ns Ar x , Ns Ar y , Ns Ar z 333 Camera position. 334 Default is @HTRDR_ARGS_DEFAULT_CAMERA_POS@. 335 .It Cm tgt= Ns Ar x , Ns Ar y , Ns Ar z 336 Targeted position. 337 Default is @HTRDR_ARGS_DEFAULT_CAMERA_TGT@. 338 .It Cm up= Ns Ar x , Ns Ar y , Ns Ar z 339 Upward vector that the top of the camera is pointing towards. 340 Default is @HTRDR_ARGS_DEFAULT_CAMERA_UP@. 341 .El 342 .It Fl p Ar flux_sensor_opt Ns Op : Ns Ar flux_sensor_opt No ... 343 Set up a flux sensor. 344 The flux is computed for the part of the sensor that is outside any 345 geometry. 346 .Pp 347 The flux sensor options are as follow: 348 .Bl -tag -width Ds 349 .It Cm pos= Ns Ar x , Ns Ar y , Ns Ar z 350 Sensor center. 351 Default is @HTRDR_ARGS_DEFAULT_RECTANGLE_POS@. 352 .It Cm tgt= Ns Ar x , Ns Ar y , Ns Ar z 353 Targeted position. 354 Default is @HTRDR_ARGS_DEFAULT_RECTANGLE_TGT@. 355 .It Cm up= Ns Ar x , Ns Ar y , Ns Ar z 356 Upward vector that the top of the sensor is pointing towards. 357 Default is @HTRDR_ARGS_DEFAULT_RECTANGLE_UP@. 358 .It Cm sz= Ns Ar width , Ns Ar height 359 Sensor size in meters. 360 Default is @HTRDR_ARGS_DEFAULT_RECTANGLE_SZ@. 361 .El 362 .It Fl s Ar spectral_opt Ns Op : Ns Ar spectral_opt No ... 363 Configure spectral integration. 364 .Pp 365 The spectral integration options are as follows: 366 .Bl -tag -width Ds 367 .It Cm cie_xyz 368 Calculate the radiance for the visible part of the spectrum between 369 .Bq 380, 780 370 nanometers using the XYZ CIE 1931 color matching functions. 371 This is the default behavior. 372 .It Cm lw= Ns Ar wlen_min , Ns Ar wlen_max 373 Calculate the radiance using the internal source of radiation, i.e. the 374 radiance emitted by the medium and its boundaries (ground and space). 375 .Pp 376 Calculations are performed between 377 .Bq Ar wlen_min , Ar wlen_max 378 nanometers according to Planck's function for a reference temperature. 379 As the application mainly concerns the earth's atmosphere, internal 380 radiation is emitted in the thermal, longwave part of the 381 electromagnetic spectrum. 382 Consequently, the default reference temperature is set at 290\ K. 383 .Pp 384 If 385 .Ar wlen_min 386 and 387 .Ar wlen_max 388 are equal, the calculation is monochromatic. 389 .It Cm sw= Ns Ar wlen_min , Ns Ar wlen_max 390 Calculate the radiance using the external source of radiance, i.e. the sun. 391 .Pp 392 Calculations are performed between 393 .Bq Ar wlen_min , Ar wlen_max 394 nanometers according to Planck's function for a reference temperature. 395 As the application mainly concerns the earth's atmosphere, the default 396 reference temperature is 5778\ K, i.e. the temperature of the sun's 397 black body. 398 .Pp 399 If 400 .Ar wlen_min 401 and 402 .Ar wlen_max 403 are equal, the calculation is monochromatic. 404 .It Cm Tref= Ns Ar temperature 405 Reference temperature when integrating with respect to the Planck function. 406 The default value is 290\ K or 5778\ K, depending on whether the 407 radiation source is internal 408 .Pq option Cm lw 409 or external 410 .Pq option Cm sw . 411 .El 412 .It Fl T Ar optical_thickness 413 Optical thickness used as threshold criterion for building acceleration 414 structures. 415 Default is @HTRDR_ATMOSPHERE_ARGS_DEFAULT_OPTICAL_THICKNESS_THRESHOLD@. 416 This option is ignored if a cache is used 417 .Pq option Fl O . 418 .It Fl t 419 Advice on the number of threads to use. 420 By default, 421 .Nm 422 uses many threads as processor cores. 423 .It Fl V Ar x , Ns Ar y , Ns Ar z 424 Maximum definition of acceleration structures. 425 By default, the finest definition is that of clouds. 426 This option is ignored if a cache is used 427 .Pq option Fl O . 428 .It Fl v 429 Make 430 .Nm 431 verbose. 432 .El 433 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 434 .\" Output image 435 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 436 .Sh OUTPUT IMAGE 437 Images calculated by 438 .Nm 439 are saved in 440 .Xr htrdr-image 5 441 format. 442 This section describes the nature and arrangement of image data 443 depending on the type of calculation performed. 444 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 445 .Ss XYZ image 446 For an image rendering in the visible part of the spectrum 447 .Pq default behavior or option Fl s Cm cie_xyz , 448 the pixel components store 4 estimates. 449 The first, second, and third pairs of floating point values encode the 450 estimated integrated radiance in W/sr/m^2 for the X, Y, and Z components 451 of the CIE 1931 XYZ color space. 452 The first value of each pair is the expected value of the 453 average radiance of the pixel. 454 The second value is its associated standard deviation. 455 The fourth and final pair records the microsecond estimate of the 456 computation time per radiative path and its standard error. 457 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 458 .Ss Longwave image 459 For infrared calculations 460 .Pq option Fl s Cm lw= Ns Ar wlen_min , Ns Ar wlen_max 461 the first and second pixel components store the expected value and the 462 standard error of the estimated brightness temperature (in K), 463 respectively. 464 The third and fourth components record the expected value and the 465 standard deviation of the pixel radiance which is either an integrated 466 radiance in W/sr/m^2 or a spectral radiance in W/sr/m^2/nm depending on 467 whether this radiance was calculated for a spectral range or at a single 468 wavelength. 469 The fifth and sixth pixel components are not used. 470 Finally, the last 2 components of the pixel record the estimate in 471 microseconds of the computation time per radiative path and its standard 472 error. 473 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 474 .Ss Shortwave image 475 For shortwave calculations 476 .Pq option Fl s Cm sw= Ns Ar wlen_min , Ns Ar wlen_max 477 the output image is formatted as for a longwave image except that the 478 first and second components of the pixels are not used, as no brightness 479 temperature has been evaluated. 480 .Ss Flux density map (shortwave and longwave) 481 A flux density map 482 .Pq option Fl p 483 store on its first and second component 484 the expected value and the standard error of the pixel radiative flux 485 density 486 .Pq in W/m^2 . 487 All other components are unused excepted the seventh and eighth 488 components that store the estimate of the radiative path computation 489 time 490 .Pq in microseconds 491 and its standard error. 492 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 493 .\" Returned status 494 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 495 .Sh EXIT STATUS 496 .Ex -std 497 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 498 .\" Examples of use 499 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 500 .Sh EXAMPLES 501 Render a clear sky scene, i.e. a scene without any cloud, whose sun is at 502 zenith. 503 The vertical atmospheric gaz mixture along the Z axis is described in 504 the 505 .Pa gas.txt 506 file. 507 The ground geometry is a quad repeated to the infinity 508 whose materials are listed in the 509 .Pa material.mtl 510 file. 511 The camera is positioned at 512 .Ar 400 513 meters height and looks toward the positive Y axis. 514 The definition of the rendered image is 515 .Ar 800 No by Ar 600 516 pixels and the radiance of each pixel component is estimated with 517 .Ar 64 518 Monte-Carlo realisations. 519 The resulting image 520 is written to 521 .Pa output 522 excepted if the file already exists; in this case an 523 error is notified, the program stops and the 524 .Pa output 525 file remains unchanged: 526 .Bd -literal -offset Ds 527 htrdr-atmosphere -D 0,90 \\ 528 -a gas.txt \\ 529 -Rg quad.obj \\ 530 -M materials.mtl \\ 531 -C pos=0,0,400:tgt=0,1,0:up=0,0,1 \\ 532 -i def=800x600:spp=64 \\ 533 -o output 534 .Ed 535 .Pp 536 Add clouds to the previous scene and use a more complex geometry to 537 represent the ground; it has been carefully designed to be cyclical and 538 can therefore be repeated ad infinitum without visual glitches. 539 Use the 540 .Fl f 541 option to write the rendered 542 image to 543 .Pa output 544 even though the file already exists. 545 Use 546 .Xr htpp 1 547 to convert the output 548 .Xr htrdr-image 5 549 in a regular PPM image: 550 .Bd -literal -offset Ds 551 htrdr-atmosphere -D 0,90 \\ 552 -a gas.txt \\ 553 -Rg mountains.obj \\ 554 -M materials.mtl \\ 555 -c clouds.htcp \\ 556 -m Mie.nc \\ 557 -C pos=0,0,400:tgt=0,1,0:up=0,0,1 \\ 558 -i def=800x600:spp=64 \\ 559 -fo output 560 htpp -o image.ppm output 561 .Ed 562 .Pp 563 Render the previous scene in infrared for the wavelengths in 564 .Bq Ar 9200 , Ar 10000 565 nanometers with a reference temperature of 566 .Ar 300 567 Kelvin: 568 .Bd -literal -offset Ds 569 htrdr-atmosphere -a gas.txt \\ 570 -Rg mountains.obj -R \\ 571 -M materials.mtl \\ 572 -c clouds.htcp \\ 573 -m Mie.nc \\ 574 -C pos=0,0,400:tgt=0,1,0:up=0,0,1 \\ 575 -i def=800x600:spp=64 \\ 576 -s lw=9200,10000:Tref=300 \\ 577 -fo output 578 .Ed 579 .Pp 580 Move the sun by setting its azimuthal and elevation angles to 581 .Ar 120 No and Ar 40 582 degrees respectively. 583 Use the 584 .Fl O 585 option to enable the cache mechanism of acceleration structures. 586 Increase the image definition to 587 .Ar 1280 No by Ar 720 588 pixels and set the number of samples per pixel component to 589 .Ar 1024 : 590 .Bd -literal -offset Ds 591 htrdr-atmosphere -D 120,40 \\ 592 -a gas.txt \\ 593 -Rg mountains.obj \\ 594 -M materials.mtl \\ 595 -c clouds.htcp \\ 596 -m Mie.nc \\ 597 -O my_cache \\ 598 -C pos=0,0,400:tgt=0,1,0:up=0,0,1 \\ 599 -i def=1280x720:spp=1024 \\ 600 -fo output 601 .Ed 602 .Pp 603 Compute the downward flux for the shortwave interval 604 .Bq Ar 350 , Ar 4000 605 nanometers on a square of 606 .Ar 100 607 meters side positioned at the origin at 608 .Ar 1 609 meter height. 610 The resolution of the flux map is 611 .Ar 500 No by Ar 500 612 pixels and 613 .Ar 1000 614 realisations is used to estimate the flux per pixel. 615 It is saved in the 616 .Pa flux_map.txt 617 file even though this file already exists: 618 .Bd -literal -offset Ds 619 htrdr-atmosphere -D 0,90 \\ 620 -a gas.txt \\ 621 -Rg plane.obj \\ 622 -M materials.mtl \\ 623 -c clouds.htcp \\ 624 -m Mie.nc \\ 625 -O my_cache \\ 626 -p pos=0,0,1:tgt=0,0,2:up=0,1,0:sz=100,100 \\ 627 -i def=500x500:spp=1000 \\ 628 -s sw=350,4000 \\ 629 -fo flux_map.txt 630 .Ed 631 .Pp 632 Write cloud acceleration structures as output. 633 Use 634 .Xr csplit 1 635 to save each of them in a specific VTK file named 636 .Pa octree Ns Ar ID , 637 .Ar ID 638 being between 639 .Bq 0, N-1 640 and N being the total number of acceleration structures (N > 1): 641 .Bd -literal -offset Ds 642 htrdr-atmosphere -a gas.txt -m Mie.nc -c clouds.htcp -d -fo output 643 N="$(grep -ce "^# vtk" output)" 644 sed /^---$/d output \\ 645 | csplit -f octree -k - %^#\\ vtk% /^#\\ vtk/ {$((${N}-2))} 646 .Ed 647 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 648 .\" References 649 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 650 .Sh SEE ALSO 651 .Xr mpirun 1 , 652 .Xr htcp 5 , 653 .Xr htmie 5 , 654 .Xr htrdr-image 5 , 655 .Xr htrdr-materials 5 , 656 .Xr htrdr-obj 5 657 .Rs 658 .%A |Méso|Star> 659 .%T High-Tune: gas optical properties file format 660 .%D November 2018 661 .%U https://www.meso-star.com/projects/htrdr/downloads/gas_opt_prop_en.pdf 662 .Re 663 .Rs 664 .%A Najda Villefranque 665 .%A Richard Fournier 666 .%A Fleur Couvreux 667 .%A Stéphane Blanco 668 .%A Céline Cornet 669 .%A Vincent Eymet 670 .%A Vincent Forest 671 .%A Jean-Marc Trégan 672 .%T A Path-Tracing Monte Carlo library for 3-D Radiative Transfer in \ 673 Highly Resolved Cloudy Atmospheres 674 .%J Journal of Advances in Modeling Earth Systems 675 .%V 11 676 .%N 8 677 .%P 2449-2473 678 .%D 2019 679 .%U https://dx.doi.org/10.1029/2018MS001602 680 .Re 681 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 682 .\" Used and implemented standards 683 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 684 .Sh STANDARDS 685 .Rs 686 .%A International Organization for Standardization / CIE 687 .%R ISO/CIE 11664-1:2019 688 .%D June 2019 689 .%T Colorimetry - Part 1: CIE standard colorimetric observers 690 .Re 691 .Pp 692 .Rs 693 .%A OpenMP Architecture Review Board 694 .%D March 2002 695 .%T OpenMP C and C++ Application Interface 696 .%O version 2.0 697 .Re 698 .Pp 699 .Rs 700 .%A Message Passing Interface Forum 701 .%D July 1997 702 .%T MPI-2: Extensions to The Message-Passing Interface 703 .Re 704 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 705 .\" Brief implementation history 706 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 707 .Sh HISTORY 708 .Nm 709 has been initially developed as part of 710 .Li ANR-16-CE01-0010 711 High-Tune project. 712 It was then extended in 713 .Li MODEVAL-URBA 2019 .