Hosek skylight model translated from C to Kotlin

2026-06-11 19:14:05 +09:00 · 2020-04-20 04:47:40 +09:00
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+This file is part of a sample implementation of the analytical skylight and
+solar radiance models presented in the SIGGRAPH 2012 paper
+
+
+           "An Analytic Model for Full Spectral Sky-Dome Radiance"
+
+and the 2013 IEEE CG&A paper
+
+       "Adding a Solar Radiance Function to the Hosek Skylight Model"
+
+                                   both by 
+
+                       Lukas Hosek and Alexander Wilkie
+                Charles University in Prague, Czech Republic
+
+
+                        Version: 1.4a, February 22nd, 2013
+                        
+Version history:
+
+1.4a  February 22nd, 2013
+      Removed unnecessary and counter-intuitive solar radius parameters 
+      from the interface of the colourspace sky dome initialisation functions.
+
+1.4   February 11th, 2013
+      Fixed a bug which caused the relative brightness of the solar disc
+      and the sky dome to be off by a factor of about 6. The sun was too 
+      bright: this affected both normal and alien sun scenarios. The 
+      coefficients of the solar radiance function were changed to fix this.
+
+1.3   January 21st, 2013 (not released to the public)
+      Added support for solar discs that are not exactly the same size as
+      the terrestrial sun. Also added support for suns with a different
+      emission spectrum ("Alien World" functionality).
+
+1.2a  December 18th, 2012
+      Fixed a mistake and some inaccuracies in the solar radiance function
+      explanations found in ArHosekSkyModel.h. The actual source code is
+      unchanged compared to version 1.2.
+
+1.2   December 17th, 2012
+      Native RGB data and a solar radiance function that matches the turbidity
+      conditions were added.
+
+1.1   September 2012
+      The coefficients of the spectral model are now scaled so that the output
+      is given in physical units: W / (m^-2 * sr * nm). Also, the output of the
+      XYZ model is now no longer scaled to the range [0...1]. Instead, it is
+      the result of a simple conversion from spectral data via the CIE 2 degree
+      standard observer matching functions. Therefore, after multiplication
+      with 683 lm / W, the Y channel now corresponds to luminance in lm.
+     
+1.0   May 11th, 2012
+      Initial release.
+
+
+Please visit http://cgg.mff.cuni.cz/projects/SkylightModelling/ to check if
+an updated version of this code has been published!
+
+This archive contains the following files:
+
+README.txt                      This file.
+
+ArHosekSkyModel.h               Header file for the reference functions. Their
+                                usage is explained there, and sample code for 
+                                calling them is given.
+
+ArHosekSkyModel.c               Implementation of the functions.
+
+ArHosekSkyModelData_Spectral.h  Spectral coefficient data.
+ArHosekSkyModelData_CIEXYZ.h    CIE XYZ coefficient data.
+ArHosekSkyModelData_RGB.h       RGB coefficient data.
+
+Please note that the source files are in C99, and you have to set appropriate 
+compiler flags for them to work. For example, when compiling this code with 
+gcc, you have to add the "-std=c99" or "-std=gnu99" flags.