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/* Copyright (c) 1986 Regents of the University of California */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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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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* 8/19/85 |
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*/ |
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#include "ray.h" |
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#include "copyright.h" |
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#include "ray.h" |
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#include "otypes.h" |
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#include "rtotypes.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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extern int |
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o_sphere( /* 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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{ |
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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 double *ap; |
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register RREAL *ap; |
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register int i; |
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if (so->oargs.nfargs != 4 || so->oargs.farg[3] <= FTINY) |
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objerror(so, USER, "bad arguments"); |
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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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* 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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* Because the ray direction is normalized, a is always 1. |
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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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a = 1.0; /* compute quadratic coefficients */ |
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b = c = 0.0; |
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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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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->rofs = 1.0; setident4(r->rofx); |
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r->robs = 1.0; setident4(r->robx); |
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r->rox = NULL; |
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r->pert[0] = r->pert[1] = r->pert[2] = 0.0; |
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r->uv[0] = r->uv[1] = 0.0; |
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return(1); /* hit */ |
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} |
