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);
}
VOID RayTrace(INT pid)
{
INT j;
INT x, y; /* Pixel address. */
REAL xx, yy;
VEC3 N; /* Normal at intersection. */
VEC3 Ipoint; /* Intersection point. */
COLOR c; /* Color for storing background. */
RAY *ray; /* Ray pointer. */
RAY rmsg; /* Ray message. */
RAYJOB job; /* Ray job from work pool. */
OBJECT *po; /* Ptr to object. */
BOOL hit; /* An object hit? */
IRECORD hitrecord; /* Intersection record. */
ray = &rmsg;
while (GetJobs(&job, pid) != WPS_EMPTY)
{
while (GetRayJobFromBundle(&job, &x, &y))
{
/* Convert the ray job to the ray message format. */
xx = (REAL)x;
yy = (REAL)y;
if (AntiAlias)
for (j = 0; j < NumSubRays; j++)
{
ConvertPrimRayJobToRayMsg(ray, xx + frand(), yy + frand());
PushRayTreeStack(ray, pid);
}
else
{
ConvertPrimRayJobToRayMsg(ray, xx, yy);
PushRayTreeStack(ray, pid);
}
while (PopRayTreeStack(ray, pid) != RTS_EMPTY)
{
/* Find which object is closest along the ray. */
switch (TraversalType)
{
case TT_LIST:
hit = Intersect(ray, &hitrecord);
break;
case TT_HUG:
hit = TraverseHierarchyUniform(ray, &hitrecord, pid);
break;
}
/* Process the object ray hit. */
if (hit)
{
/*
* Get parent object to be able to access
* object operations.
*/
po = hitrecord.pelem->parent;
/* Calculate intersection point. */
RayPoint(Ipoint, ray, hitrecord.t);
/* Calculate normal at this point. */
((void (*)(IRECORD *, VEC3, VEC3))(*po->procs->normal))(&hitrecord, Ipoint, N);
/* Make sure normal is pointing toward ray origin. */
if ((VecDot(ray->D, N)) > 0.0)
VecNegate(N, N);
/*
* Compute shade at this point - will process
* shadow rays and add secondary reflection
* and refraction rays to ray tree stack
*/
Shade(Ipoint, N, ray, &hitrecord, pid);
}
else
{
/* Add background as pixel contribution. */
VecCopy(c, View.bkg);
VecScale(c, ray->weight, c);
AddPixelColor(c, ray->x, ray->y);
}
}
}
}
}
