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# cstool/fogmath.h

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    00001 /*
    00002     Copyright (C) 2004 by Anders Stenberg
    00003
    00004     This library is free software; you can redistribute it and/or
    00005     modify it under the terms of the GNU Library General Public
    00006     License as published by the Free Software Foundation; either
    00007     version 2 of the License, or (at your option) any later version.
    00008
    00009     This library is distributed in the hope that it will be useful,
    00010     but WITHOUT ANY WARRANTY; without even the implied warranty of
    00011     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    00012     Library General Public License for more details.
    00013
    00014     You should have received a copy of the GNU Library General Public
    00015     License along with this library; if not, write to the Free
    00016     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
    00017 */
    00018
    00019 #ifndef __CS_CSTOOL_FOGMATH_H__
    00020 #define __CS_CSTOOL_FOGMATH_H__
    00021
    00026
    00027 class csFogMath
    00028 {
    00029 public:
    00033   static inline float Ramp (float depth)
    00034   {
    00035     return 1.0 - exp (-depth*7);
    00036     //return depth;
    00037   }
    00039   /* @@@ NOTE: Basically the same computation that's done when using fog
    00040    * texgen from the glfixed VP - means, keep this function in sync! */
    00041   static inline float OpacityAtDistance (float density, float dist)
    00042   {
    00043     return Ramp (density*(dist-0.1f));
    00044   }
    00046   static inline float DistanceForOpacity (float density, float opacity)
    00047   {
    00048     return -(log(-opacity+1.0f)/(density * 7.0f)) + 0.1f;
    00049   }
    00050 };
    00051
    00052
    00053 #endif // __CS_CSTOOL_FOGMATH_H__
    00054