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#ifndef lint
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static const char RCSid[] = "$Id: o_face.c,v 2.6 2006/03/02 16:51:55 greg Exp $";
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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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#include "copyright.h"
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#include "ray.h"
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#include "face.h"
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#include "rtotypes.h"
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int
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o_face( /* compute intersection with polygonal face */
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OBJREC *o,
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RAY *r
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)
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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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FACE *f; /* face record */
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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->offset) / 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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VSUM(pisect, r->rorg, r->rdir, t);
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if (!inface(pisect, f)) /* ray intersects face? */
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return(0);
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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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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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r->rox = NULL;
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return(1); /* hit */
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}
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