INT SphPeIntersect(RAY *pr, ELEMENT *pe, IRECORD *hit)
{
INT nhits; /* Number of hits. */
REAL b, disc, t1, t2, vsq; /* Formula variables. */
SPHERE *ps; /* Ptr to sphere data. */
POINT V; /* C - P */
IRECORD *sphhit;
ps = (SPHERE *)(pe->data);
sphhit = hit;
VecSub(V, ps->center, pr->P); /* Ray from origin to center.*/
vsq = VecDot(V, V); /* Length sq of V. */
b = VecDot(V, pr->D); /* Perpendicular scale of V. */
if (vsq > ps->rad2 && b < RAYEPS) /* Behind ray origin. */
return (0);
disc = b*b - vsq + ps->rad2; /* Discriminate. */
if (disc < 0.0) /* Misses ray. */
return (0);
disc = sqrt(disc); /* Find intersection param. */
t2 = b + disc;
t1 = b - disc;
if (t2 <= RAYEPS) /* Behind ray origin. */
return (0);
nhits = 0;
if (t1 > RAYEPS) /* Entering sphere. */
{
IsectAdd(sphhit, t1, pe);
sphhit++;
nhits++;
}
IsectAdd(sphhit, t2, pe); /* Exiting sphere */
nhits++;
return (nhits);
}
INT PolyPeIntersect(RAY *pr, ELEMENT *pe, IRECORD *hit)
{
INT i;
INT *vindex; /* Vertex index pointer. */
INT toright; /* Counter. */
INT sh, nsh; /* Sign holders. */
REAL Rd_dot_Pn; /* Polygon normal dot ray direction. */
REAL Ro_dot_Pn; /* Polygon normal dot ray origin. */
REAL tval; /* Intersection t distance value. */
REAL x[MAX_VERTS + 1]; /* Projection list. */
REAL y[MAX_VERTS + 1]; /* Projection list. */
REAL ix, iy; /* Intersection projection point. */
REAL dx, dy; /* Deltas between 2 vertices. */
REAL xint; /* Intersection value. */
VEC3 I; /* Intersection point. */
VEC3 *vlist, *vpos; /* Vertex list pointer. */
POLY *pp; /* Ptr to polygon data. */
pp = (POLY *)pe->data;
Rd_dot_Pn = VecDot(pp->norm, pr->D);
if (ABS(Rd_dot_Pn) < RAYEPS) /* Ray is parallel. */
return (0);
Ro_dot_Pn = VecDot(pp->norm, pr->P);
tval = -(pp->d + Ro_dot_Pn)/Rd_dot_Pn; /* Intersection distance. */
if (tval < RAYEPS) /* Intersects behind ray. */
return (0);
RayPoint(I, pr, tval);
/* Polygon containment. */
/* Project onto plane with greatest normal component. */
vlist = pp->vptr;
vindex = pp->vindex;
switch (pp->axis_proj)
{
case X_AXIS:
for (i = 0; i < pp->nverts; i++)
{
vpos = vlist + (*vindex);
x[i] = (*vpos)[1];
y[i] = (*vpos)[2];
vindex++;
}
ix = I[1];
iy = I[2];
break;
case Y_AXIS:
for (i = 0; i < pp->nverts; i++)
{
vpos = vlist + (*vindex);
x[i] = (*vpos)[0];
y[i] = (*vpos)[2];
vindex++;
}
ix = I[0];
iy = I[2];
break;
case Z_AXIS:
for (i = 0; i < pp->nverts; i++)
{
vpos = vlist + (*vindex);
x[i] = (*vpos)[0];
y[i] = (*vpos)[1];
vindex++;
}
ix = I[0];
iy = I[1];
break;
}
/* Translate to origin. */
for (i = 0; i < pp->nverts; i++)
{
x[i] -= ix;
y[i] -= iy;
if (ABS(y[i]) < RAYEPS)
y[i] = 0.0;
}
x[pp->nverts] = x[0];
y[pp->nverts] = y[0];
/*
* If intersection point crosses an odd number of line segments,
* the point is inside the polygon
*/
if (y[0] < 0.0)
sh = 0;
else
sh = 1;
toright = 0;
for (i = 0; i < pp->nverts; i++)
{
/* Check if segment crosses in y. */
if (y[i + 1] < 0.0)
nsh = 0;
else
nsh = 1;
if (nsh ^ sh)
{
dy = y[i + 1] - y[i];
if (ABS(dy) >= RAYEPS)
{
dx = x[i + 1] - x[i];
xint = x[i] - y[i]*dx / dy;
if (xint > 0.0)
toright++;
}
}
sh = nsh;
}
if (toright%2 == 1)
{
IsectAdd(hit, tval, pe);
return (1);
}
else
return (0);
}
