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greg |
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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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#endif |
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/* |
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* o_face.c - compute ray intersection with faces. |
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* |
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* 8/29/85 |
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*/ |
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#include "ray.h" |
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#include "face.h" |
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o_face(o, r) /* compute intersection with polygonal face */ |
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OBJREC *o; |
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register RAY *r; |
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{ |
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double rdot; /* direction . normal */ |
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double t; /* distance to intersection */ |
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FVECT pisect; /* intersection point */ |
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register FACE *f; /* face record */ |
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register int i; |
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f = getface(o); |
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/* |
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* First, we find the distance to the plane containing the |
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* face. If this distance is less than zero or greater |
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* than a previous intersection, we return. Otherwise, |
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* we determine whether in fact the ray intersects the |
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* face. The ray intersects the face if the |
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* point of intersection with the plane of the face |
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* is inside the face. |
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*/ |
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/* compute dist. to plane */ |
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rdot = -DOT(r->rdir, f->norm); |
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if (rdot <= FTINY && rdot >= -FTINY) /* ray parallels plane */ |
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t = FHUGE; |
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else |
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t = (DOT(r->rorg, f->norm) - f->const) / rdot; |
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if (t <= FTINY || t >= r->rot) /* not good enough */ |
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return(0); |
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/* compute intersection */ |
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for (i = 0; i < 3; i++) |
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pisect[i] = r->rorg[i] + r->rdir[i]*t; |
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if (inface(pisect, f)) { /* ray intersects face? */ |
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r->ro = o; |
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r->rot = t; |
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VCOPY(r->rop, pisect); |
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VCOPY(r->ron, f->norm); |
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r->rod = rdot; |
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} |
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return(1); /* hit */ |
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} |
