schiff.1.in (8845B)
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If not, see <http://www.gnu.org/licenses/>. 20 .Dd May 15, 2026 21 .Dt SCHIFF 1 22 .Os 23 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 24 .Sh NAME 25 .Nm schiff 26 .Nd estimate radiative properties of soft particles 27 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 28 .Sh SYNOPSIS 29 .Nm 30 .Op Fl Dhqv 31 .Op Fl a Ar nangles_phase_func 32 .Op Fl A Ar nangles_phase_func_invcumul 33 .Op Fl d Ar ninner_samples 34 .Op Fl g Ar nrealisations 35 .Op Fl G Ar nparticles 36 .Op Fl i Ar distribution 37 .Op Fl l Ar particles_length 38 .Op Fl n Ar nthreads 39 .Op Fl o Ar output 40 .Op Fl w Ar wavelelength Ns Op : Ns Ar wavelelength No ... 41 .Op Ar optical_props 42 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 43 .Sh DESCRIPTION 44 .Nm 45 computes the radiative properties of soft particles with an 46 .Dq Approximation Method for Short Wavelength or High Energy Scattering 47 .Pq Schiff, 1956 . 48 The implemented model is detailed in 49 .Dq Monte Carlo Implementation of Schiff's Approximation for \ 50 Estimating Radiative Properties of Homogeneous, Simple-Shaped and \ 51 Optically Soft Particles: Application to Photosynthetic \ 52 Micro-Organisms 53 .Pq Charon et al., 2015 . 54 It relies on the Monte Carlo method to solve Maxwell's equations within 55 Schiff's approximation; it estimates total cross sections 56 .Pq extinction, absorption and scattering cross-sections 57 in addition of the inverse cumulative phase function. 58 .Pp 59 The shapes of the soft particles are controlled by the 60 .Xr schiff-geometry 5 61 file submitted by the 62 .Fl i 63 option. 64 The per wavelength optical properties 65 of the soft particles are stored in 66 .Ar optical_props 67 where each line is formatted as 68 .Dq W N K Ne 69 with 70 .Dq W 71 is the wavelength in vacuum expressed in micron, 72 .Dq N 73 and 74 .Dq K 75 are the real and imaginary parts, respectively, of the refractive index, 76 and 77 .Dq Ne 78 the refractive index of the medium. 79 With no 80 .Ar optical_props , 81 the optical properties are read from standard input. 82 .Pp 83 The estimated results follows the 84 .Xr schiff-output 5 85 format and are written to the 86 .Ar output 87 file or to standard ouptut whether 88 the 89 .Fl o 90 is defined or not, respectively. 91 .Pp 92 The options are as follows: 93 .Bl -tag -width Ds 94 .\"""""""""""""""""""""""""""""""""" 95 .It Fl a Ar nangles_phase_func 96 Number of phase function scattering angles to estimate. 97 These angles are 98 uniformaly distributed in 99 .Bq 0,PI , 100 i.e. the value of the i^th angle 101 .Pq i in Bq 0, Ns Ar nangles_phase_func 102 is 103 .No i*PI/ Ns Pq Ar nangles_phase_func Ns -1 . 104 Default is @SCHIFF_ARGS_DEFAULT_NANGLES@. 105 .\"""""""""""""""""""""""""""""""""" 106 .It Fl A Ar nangles_phase_func_invcumul 107 Number of scattering angles computed from the inverse cumulative phase 108 function. 109 The value of the i^th angle 110 .Pq i in Bq 0, Ns Ar nangles_phase_func_invcumul Ns -1 111 is 112 .No CDF^-1 Ns Po i/ Ns Po Ar nangles_phase_func_invcumul Ns -1 Pc Pc . 113 Default is @SCHIFF_ARGS_DEFAULT_NANGLES_INV@. 114 .\"""""""""""""""""""""""""""""""""" 115 .It Fl d Ar ninner_samples 116 Number of conditioned integration variable sampling 117 .Pq incident direction, volume, ray Ns Pq s 118 for each sampled particle-shape. 119 Calculation of optimal value is presented in 120 .Dq Monte Carlo efficiency improvement by multiple sampling \ 121 of conditioned integration variables 122 .Pq Weitz et al., 2016 . 123 Default is @SCHIFF_ARGS_DEFAULT_NINSAMPLES@. 124 .\"""""""""""""""""""""""""""""""""" 125 .It Fl D 126 discard computations of the 127 .Bq Ns Bo inverse- Bc Ns cumulative 128 phase functions for large scattering angles. 129 See the 130 .Fl l 131 option for the definition of large scattering angles. 132 .\"""""""""""""""""""""""""""""""""" 133 .It Fl g Ar nrealisations 134 Number of sampled particle-shapes. 135 This the number of realisations of the Monte Carlo algorithm. 136 Default is @SCHIFF_ARGS_DEFAULT_NREALISATIONS@. 137 .\"""""""""""""""""""""""""""""""""" 138 .It Fl G Ar nparticles 139 Sample 140 .Ar nparticles 141 soft particles with respect to the defined distribution, dump their 142 geometric data and exit. 143 The data are written to 144 .Ar output 145 or the standard output whether the 146 .Fl o 147 option is defined or not, respectively. 148 The outputted data followed the Alias Wavefront obj file format. 149 .\"""""""""""""""""""""""""""""""""" 150 .It Fl h 151 Display short help and exit. 152 .\"""""""""""""""""""""""""""""""""" 153 .It Fl i Ar distribution 154 Define the 155 .Xr schiff-geometry 5 156 file that controls the geometry distribution of the soft particles. 157 .\"""""""""""""""""""""""""""""""""" 158 .It Fl l Ar particles_length 159 Characteristic length in micron of the soft particles. 160 Used for the definition of the angle that sets the limit between small 161 and large scattering angles 162 .Po 163 see equation 7 in 164 .Dq Approximation for Estimating Radiative Properties of Homogeneous, \ 165 Simple-Shaped and Optically Soft Particles: Application to \ 166 Photosynthetic Micro-Organisms , 167 Charon et al. 2015 168 .Pc . 169 .\"""""""""""""""""""""""""""""""""" 170 .It Fl n Ar nthreads 171 Hint on the number of threads to use during the integration. 172 Advice on the number of threads to use. 173 By default, 174 .Nm 175 uses as many threads as processor cores. 176 .\"""""""""""""""""""""""""""""""""" 177 .It Fl o Ar output 178 Output file. 179 If not defined, the results are written to standard output. 180 .\"""""""""""""""""""""""""""""""""" 181 .It Fl q 182 Do not print the helper message when no 183 .Ar optical_props 184 is submitted. 185 .\"""""""""""""""""""""""""""""""""" 186 .It Fl w Ar wavelelength Ns Op : Ns Ar wavelelength No ... 187 List of wavelengths in vacuum 188 .Pq expressed in micron 189 to integrate. 190 .\"""""""""""""""""""""""""""""""""" 191 .It Fl v 192 Display version information and exit. 193 .El 194 .Sh EXIT STATUS 195 .Ex -std 196 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 197 .Sh EXAMPLES 198 Estimate the radiative properties of soft particles whose shape is 199 described in the 200 .Pa geometry.yaml 201 file and its optical properties in the 202 .Pa properties 203 file. 204 The characteristic length of the soft particle shapes is 2.3 microns 205 and the estimations is performed for the wavelengths 0.45 and 0.6 206 microns. 207 The results are written to the standard output: 208 .Bd -literal -offset Ds 209 schiff -i geometry.yaml -l 2.3 -w 0.45:0.6 properties 210 .Ed 211 .\"""""""""""""""""""""""""""""""""" 212 .Pp 213 The soft particles have a characteristic length of 1 and their shape is 214 controlled by the 215 .Pa my_geom.yaml 216 file. 217 Their optical properties are read from the standard input. 218 The estimated wavelelength is 0.66 microns and the results are written 219 to the 220 .Pa my_result 221 file: 222 .Bd -literal -offset Ds 223 schiff -w 0.66 -l 1.0 -i my_geom.yaml -o my_result 224 .Ed 225 .\"""""""""""""""""""""""""""""""""" 226 .Pp 227 Sample 10 228 soft particles whose shape is defined by the 229 .Pa geometry.yaml 230 file and write their triangulated geometric data to the 231 .Pa output 232 file. 233 Use the 234 .Xr csplit 1 235 command to split the 236 .Pa output 237 file in 10 files named 238 .No particle Ns Ar N , 239 with 240 .Ar N 241 in 242 .Bq 0,9 , 243 each storing the geometric data of a sampled soft particle: 244 .Bd -literal -offset Ds 245 schiff -i geometry.yaml -G 10 -o output 246 N="$(grep -ce "^g " output)" 247 csplit -f particle -k -n1 output %^g\e % /^g\e / {$((N-2))} 248 .Ed 249 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 250 .Sh SEE ALSO 251 .Xr csplit 1 , 252 .Xr schiff-geometry 5 , 253 .Xr schiff-output 5 254 .Rs 255 .%A Leonard Isaac Schiff 256 .%T Approximation Method for Short Wavelength or High-Energy Scattering 257 .%J Physical Review 258 .%V 104 259 .%P pp. 1481\(en1485 260 .%D 1956 261 .Re 262 .Rs 263 .%A Julien Charon et al. 264 .%T Approximation for Estimating Radiative Properties of Homogeneous, \ 265 Simple-Shaped and Optically Soft Particles: Application to \ 266 Photosynthetic Micro-Organisms 267 .%J Journal of Quantitative Spectroscopy and Radiative Transfer 268 .%V 172 269 .%P pp. 3\(en23 270 .%D 2015 271 .Re 272 .Rs 273 .%A Sebastian Weitz et al. 274 .%T Monte Carlo efficiency improvement by multiple sampling of \ 275 conditioned integration variables 276 .%J Journal of Computational Physics 277 .%V 326 278 .%P pp. 30\(en34 279 .%D 2016 280 .Re 281 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 282 .Sh HISTORY 283 .Nm 284 has been developed as part of 285 .Li ANR-11-IDEX-0002-02 286 ALGUE project.