int
o_face( /* determine if face intersects cube */
OBJREC *o,
CUBE *cu
)
{
FVECT cumin, cumax;
FVECT v1, v2;
double d1, d2;
int vloc;
register FACE *f;
register int i, j;
/* get face arguments */
f = getface(o);
if (f->area == 0.0) /* empty face */
return(O_MISS);
/* compute cube boundaries */
for (j = 0; j < 3; j++)
cumax[j] = (cumin[j] = cu->cuorg[j]-FTINY)
+ cu->cusize + 2.0*FTINY;
vloc = ABOVE | BELOW; /* check vertices */
for (i = 0; i < f->nv; i++)
if ( (j = plocate(VERTEX(f,i), cumin, cumax)) )
vloc &= j;
else
return(O_HIT); /* vertex inside */
if (vloc) /* all to one side */
return(O_MISS);
for (i = 0; i < f->nv; i++) { /* check edges */
if ((j = i + 1) >= f->nv)
j = 0; /* wrap around */
VCOPY(v1, VERTEX(f,i)); /* clip modifies */
VCOPY(v2, VERTEX(f,j)); /* the vertices! */
if (clip(v1, v2, cumin, cumax))
return(O_HIT); /* edge inside */
}
/* see if cube cuts plane */
for (j = 0; j < 3; j++)
if (f->norm[j] > 0.0) {
v1[j] = cumin[j];
v2[j] = cumax[j];
} else {
v1[j] = cumax[j];
v2[j] = cumin[j];
}
if ((d1 = DOT(v1, f->norm) - f->offset) > FTINY)
return(O_MISS);
if ((d2 = DOT(v2, f->norm) - f->offset) < -FTINY)
return(O_MISS);
/* intersect face */
for (j = 0; j < 3; j++)
v1[j] = (v1[j]*d2 - v2[j]*d1)/(d2 - d1);
if (inface(v1, f))
return(O_HIT);
return(O_MISS); /* no intersection */
}
extern int
o_face( /* compute intersection with polygonal face */
OBJREC *o,
register RAY *r
)
{
double rdot; /* direction . normal */
double t; /* distance to intersection */
FVECT pisect; /* intersection point */
register FACE *f; /* face record */
f = getface(o);
/*
* First, we find the distance to the plane containing the
* face. If this distance is less than zero or greater
* than a previous intersection, 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 */
t = FHUGE;
else
t = (DOT(r->rorg, f->norm) - f->offset) / rdot;
if (t <= FTINY || t >= r->rot) /* not good enough */
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 */
}
