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sky.c
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C/C++ Source or Header
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1991-08-08
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2KB
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75 lines
/*
* sky.c
*
* Copyright (C) 1989, 1991, Craig E. Kolb
* All rights reserved.
*
* This software may be freely copied, modified, and redistributed
* provided that this copyright notice is preserved on all copies.
*
* You may not distribute this software, in whole or in part, as part of
* any commercial product without the express consent of the authors.
*
* There is no warranty or other guarantee of fitness of this software
* for any purpose. It is provided solely "as is".
*
* $Id: sky.c,v 4.0 91/07/17 14:43:43 kolb Exp Locker: kolb $
*
* $Log: sky.c,v $
* Revision 4.0 91/07/17 14:43:43 kolb
* Initial version.
*
*/
#include "texture.h"
#include "sky.h"
Sky *
SkyCreate(scale, h, lambda, octaves, cthresh, lthresh)
Float h, lambda, scale, cthresh, lthresh;
int octaves;
{
Sky *sky;
sky = (Sky *)Malloc(sizeof(Sky));
sky->beta = 1. + 2 * h;
sky->omega = pow(lambda, -0.5 * sky->beta);
sky->lambda = lambda;
sky->scale = scale;
sky->cthresh = cthresh;
sky->lthresh = lthresh;
sky->octaves = octaves;
return sky;
}
void
SkyApply(sky, prim, ray, pos, norm, gnorm, surf)
Sky *sky;
Geom *prim;
Ray *ray;
Vector *pos, *norm, *gnorm;
Surface *surf;
{
Float It, maxval;
It = fBm(pos, sky->omega, sky->lambda, sky->octaves);
maxval = 1. / (1. - sky->omega);
/*
* Map from [-maxval,maxval] to [0,1]
*/
It = (maxval + It) * 0.5/maxval;
It = (It - sky->lthresh) / (sky->cthresh - sky->lthresh);
if (It < 0.)
It = 0;
else if (It > 1.)
It = 1;
if (sky->scale != 0.)
It = pow(It, sky->scale);
surf->transp = 1. - It;
ColorScale(It, surf->diff, &surf->diff);
ColorScale(It, surf->amb, &surf->amb);
}