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#ifndef lint |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* sphere.c - compute ray intersection with spheres. |
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*/ |
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/* ==================================================================== |
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* The Radiance Software License, Version 1.0 |
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* |
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* Copyright (c) 1990 - 2002 The Regents of the University of California, |
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* through Lawrence Berkeley National Laboratory. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* |
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* 3. The end-user documentation included with the redistribution, |
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* if any, must include the following acknowledgment: |
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* "This product includes Radiance software |
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* (http://radsite.lbl.gov/) |
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* developed by the Lawrence Berkeley National Laboratory |
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* (http://www.lbl.gov/)." |
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* Alternately, this acknowledgment may appear in the software itself, |
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* if and wherever such third-party acknowledgments normally appear. |
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* |
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* 4. The names "Radiance," "Lawrence Berkeley National Laboratory" |
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* and "The Regents of the University of California" must |
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* not be used to endorse or promote products derived from this |
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* software without prior written permission. For written |
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* permission, please contact [email protected]. |
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* |
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* 5. Products derived from this software may not be called "Radiance", |
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* nor may "Radiance" appear in their name, without prior written |
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* permission of Lawrence Berkeley National Laboratory. |
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* |
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR |
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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* ==================================================================== |
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* |
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* This software consists of voluntary contributions made by many |
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* individuals on behalf of Lawrence Berkeley National Laboratory. For more |
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* information on Lawrence Berkeley National Laboratory, please see |
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* <http://www.lbl.gov/>. |
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*/ |
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#include "ray.h" |
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#include "otypes.h" |
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o_sphere(so, r) /* compute intersection with sphere */ |
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OBJREC *so; |
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register RAY *r; |
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{ |
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double a, b, c; /* coefficients for quadratic equation */ |
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double root[2]; /* quadratic roots */ |
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int nroots; |
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double t; |
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register FLOAT *ap; |
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register int i; |
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if (so->oargs.nfargs != 4) |
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objerror(so, USER, "bad # arguments"); |
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ap = so->oargs.farg; |
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if (ap[3] < -FTINY) { |
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objerror(so, WARNING, "negative radius"); |
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so->otype = so->otype == OBJ_SPHERE ? |
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OBJ_BUBBLE : OBJ_SPHERE; |
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ap[3] = -ap[3]; |
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} else if (ap[3] <= FTINY) |
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objerror(so, USER, "zero radius"); |
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/* |
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* We compute the intersection by substituting into |
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* the surface equation for the sphere. The resulting |
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* quadratic equation in t is then solved for the |
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* smallest positive root, which is our point of |
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* intersection. |
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* Since the ray is normalized, a should always be |
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* one. We compute it here to prevent instability in the |
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* intersection calculation. |
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*/ |
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/* compute quadratic coefficients */ |
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a = b = c = 0.0; |
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for (i = 0; i < 3; i++) { |
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a += r->rdir[i]*r->rdir[i]; |
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t = r->rorg[i] - ap[i]; |
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b += 2.0*r->rdir[i]*t; |
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c += t*t; |
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} |
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c -= ap[3] * ap[3]; |
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nroots = quadratic(root, a, b, c); /* solve quadratic */ |
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for (i = 0; i < nroots; i++) /* get smallest positive */ |
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if ((t = root[i]) > FTINY) |
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break; |
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if (i >= nroots) |
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return(0); /* no positive root */ |
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if (t >= r->rot) |
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return(0); /* other is closer */ |
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r->ro = so; |
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r->rot = t; |
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/* compute normal */ |
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a = ap[3]; |
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if (so->otype == OBJ_BUBBLE) |
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a = -a; /* reverse */ |
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for (i = 0; i < 3; i++) { |
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r->rop[i] = r->rorg[i] + r->rdir[i]*t; |
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r->ron[i] = (r->rop[i] - ap[i]) / a; |
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} |
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r->rod = -DOT(r->rdir, r->ron); |
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r->rox = NULL; |
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return(1); /* hit */ |
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} |