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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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|
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#include "copyright.h" |
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|
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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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|
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|
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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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|
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f = getface(o); |
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|
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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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|
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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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|
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if (!inface(pisect, f)) /* ray intersects face? */ |
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return(0); |
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|
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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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|
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return(1); /* hit */ |
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} |
