RadiancePmap/o_face.c
46ae0123f8a4fixSpecular

o_face.c
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			#ifndef lint
			static const char RCSid[] = "$Id: o_face.c,v 2.8 2021/01/31 18:08:04 greg Exp $";
			#endif
			/*
			* o_face.c - compute ray intersection with faces.
			*/

			#include "copyright.h"

			#include "ray.h"
			#include "face.h"
			#include "rtotypes.h"


			int
			o_face( /* compute intersection with polygonal face */
			OBJREC *o,
			RAY *r
			)
			{
			double rdot; /* direction . normal */
			double t; /* distance to intersection */
			FVECT pisect; /* intersection point */
			FACE f; / face record */

			f = getface(o);

			/*
			* First, we find the distance to the plane containing the
			* face. If the plane is parallel to our ray, or the
			* previous hit was better, we return. Otherwise,
			* we determine whether in fact the ray intersects the
			* face. The ray intersects the face if the
			* point of intersection with the plane of the face
			* is inside the face.
			*/
			/* compute dist. to plane */
			rdot = -DOT(r->rdir, f->norm);
			if ((rdot <= FTINY) & (rdot >= -FTINY)) /* ray parallels plane */
			return(0);

			t = (DOT(r->rorg, f->norm) - f->offset) / rdot;

			if (rayreject(o, r, t)) /* previous hit is better? */
			return(0);
			/* compute intersection */
			VSUM(pisect, r->rorg, r->rdir, t);

			if (!inface(pisect, f)) /* ray intersects face? */
			return(0);

			r->ro = o;
			r->rot = t;
			VCOPY(r->rop, pisect);
			VCOPY(r->ron, f->norm);
			r->rod = rdot;
			r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
			r->uv[0] = r->uv[1] = 0.0;
			r->rox = NULL;

			return(1); /* hit */
			}