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/*
* cloud.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".
*
* $Id$
*
* $Log$
*/
#include "texture.h"
#include "cloud.h"
/*
* Gardner-style textured ellipsoid. Designed to be used on unit spheres
* centered at the origin. (Of course, the spheres may be transformed
* into ellipsoids, translated, etc.)
*/
CloudText *
CloudTextCreate(scale, h, lambda, octaves, cthresh, lthresh, transcale)
Float scale, h, lambda, cthresh, lthresh, transcale;
int octaves;
{
CloudText *cloud;
cloud = (CloudText *)Malloc(sizeof(CloudText));
cloud->beta = 1. + 2 * h;
cloud->omega = pow(lambda, -0.5 * cloud->beta);
cloud->lambda = lambda;
cloud->scale = scale;
cloud->cthresh = cthresh;
cloud->range = lthresh - cthresh;
cloud->transcale = transcale;
cloud->maxval = 1. / (1. - cloud->beta);
cloud->octaves = octaves;
return cloud;
}
void
CloudTextApply(cloud, prim, ray, pos, norm, gnorm, surf)
CloudText *cloud;
Object *prim;
Ray *ray;
Vector *pos, *norm, *gnorm;
Surface *surf;
{
Ray pray;
Float alpha, beta, It, dsquared, d, limb;
/*
* Transform ray to prim. space.
*/
pray = *ray;
(void)TextRayToPrim(&pray);
dsquared = dotp(&pray.pos, &pray.pos);
if (fabs(dsquared) < 1. + EPSILON) {
surf->transp = 1.;
surf->amb.r = surf->amb.g = surf->amb.b = 0.;
surf->diff.r = surf->diff.g = surf->diff.b = 0.;
return;
}
It = fBm(pos,cloud->omega,cloud->lambda,cloud->octaves);
It = (cloud->maxval + It) * 0.5/cloud->maxval;
if (It < 0.)
It = 0;
else if (It > 1.)
It = 1;
d = sqrt(dsquared);
beta = sqrt(dsquared - 1) / d;
alpha = -dotp(&pray.pos, &pray.dir) / d;
limb = (alpha - beta) / (1 - beta);
/*
* limb is 0 on the limb, 1 at the center, < 1 outside.
*/
surf->transp = 1. - (It-cloud->cthresh-cloud->range*(1.-limb))/
cloud->transcale;
if (surf->transp > 1)
surf->transp = 1.;
if (surf->transp < 0)
surf->transp = 0.;
ColorScale((1. - surf->transp) *
(1. - cloud->scale + cloud->scale*It),
surf->diff, &surf->diff);
ColorScale(1. - surf->transp, surf->amb, &surf->amb);
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.