I you're destinations are convex then just check the point-plane distance of each polygon in the destination, and if the point is on the same side of all polygons then it's inside.
If they're concave, then the easiest is probably to divide them into convex subsections, for example with a BSP tree.
bool __fastcall IntersectedPolygon(LIGHT_TRAIL vPoly, t3dpoint vLine[2],int verticeCount)
{
Extended MATCH_FACTOR = 0.9999999999;
t3dpoint vNormal;
t3dpoint vIntersection;
Extended originDistance;
Extended distance1;
Extended distance2;
t3dpoint vVector1;
t3dpoint vVector2;
double m_magnitude;
t3dpoint vPoint;
t3dpoint vLineDir;
Extended Numerator;
Extended Denominator;
Extended dist;
Extended Angle,tempangle;
t3dpoint vA, vB;
int i;
Extended dotProduct;
Extended vectorsMagnitude;
vNormal.x = 0.0;
vNormal.y = 0.0;
vNormal.z = 0.0;
originDistance = 0.0;
distance1 = 0.0;
distance2 = 0.0;
vPoint.x = 0.0f;
vPoint.y = 0.0f;
vPoint.z = 0.0f;
vLineDir.x = 0.0f;
vLineDir.y = 0.0f;
vLineDir.z = 0.0f;
Numerator = 0.0;
Denominator = 0.0;
dist = 0.0;
Angle = 0.0;
vVector1.x = vPoly[2].x - vPoly[0].x;
vVector1.y = vPoly[2].y - vPoly[0].y;
vVector1.z = vPoly[2].z - vPoly[0].z;
vVector2.x = vPoly[1].x - vPoly[0].x;
vVector2.y = vPoly[1].y - vPoly[0].y;
vVector2.z = vPoly[1].z - vPoly[0].z;
vNormal.x = ((vVector1.y * vVector2.z) - (vVector1.z * vVector2.y));
vNormal.y = ((vVector1.z * vVector2.x) - (vVector1.x * vVector2.z));
vNormal.z = ((vVector1.x * vVector2.y) - (vVector1.y * vVector2.x));
m_magnitude = sqrt((vNormal.x * vNormal.x) +
(vNormal.y * vNormal.y) +
(vNormal.z * vNormal.z) );
vNormal.x = vNormal.x/m_magnitude;
vNormal.y = vNormal.y/m_magnitude;
vNormal.z = vNormal.z/m_magnitude;
if ( (IsNan(vNormal.x)== true) || (IsNan(vNormal.y)== true) || (IsNan(vNormal.z)== true) )
{
return false;
}
originDistance = -1.0f * ((vNormal.x * vPoly[0].x) +
(vNormal.y * vPoly[0].y) +
(vNormal.z * vPoly[0].z));
distance1 = ((vNormal.x * vLine[0].x) +
(vNormal.y * vLine[0].y) +
(vNormal.z * vLine[0].z)) + originDistance;
distance2 = ((vNormal.x * vLine[1].x) +
(vNormal.y * vLine[1].y) +
(vNormal.z * vLine[1].z)) + originDistance;
if(distance1 * distance2 >= 0.0f)
return false;
vLineDir.x = vLine[1].x - vLine[0].x;
vLineDir.y = vLine[1].y - vLine[0].y;
vLineDir.z = vLine[1].z - vLine[0].z;
m_magnitude = sqrt((vLineDir.x * vLineDir.x) +
(vLineDir.y * vLineDir.y) +
(vLineDir.z * vLineDir.z) );
vLineDir.x = vLineDir.x/m_magnitude;
vLineDir.y = vLineDir.y/m_magnitude;
vLineDir.z = vLineDir.z/m_magnitude;
Numerator = -1.0f * (vNormal.x * vLine[0].x +
vNormal.y * vLine[0].y +
vNormal.z * vLine[0].z + originDistance);
Denominator = ( (vNormal.x * vLineDir.x) + (vNormal.y * vLineDir.y) + (vNormal.z * vLineDir.z) );
if( Denominator == 0.0f) {
vIntersection = vLine[0];
temp_intersect_v = vIntersection;
} else {
dist = Numerator / Denominator;
vPoint.x = (vLine[0].x + (vLineDir.x * dist));
vPoint.y = (vLine[0].y + (vLineDir.y * dist));
vPoint.z = (vLine[0].z + (vLineDir.z * dist));
temp_intersect_v = vPoint; // Return the intersection point
}
//temp_intersect_v.x := vIntersection.x;
//temp_intersect_v.y := vIntersection.y;
//temp_intersect_v.z := vIntersection.z;
//temp_intersect_v2 := vPoint;
//CLIP_INTERSECT_POS := temp_intersect_v;
for (i = 0; i < verticeCount; i++) {
vA.x = vPoly[i].x - temp_intersect_v.x;
vA.y = vPoly[i].y - temp_intersect_v.y;
vA.z = vPoly[i].z - temp_intersect_v.z;
vB.x = vPoly[(i + 1) % verticeCount].x - temp_intersect_v.x;
vB.y = vPoly[(i + 1) % verticeCount].y - temp_intersect_v.y;
vB.z = vPoly[(i + 1) % verticeCount].z - temp_intersect_v.z;
dotProduct = ( (vA.x * vB.x) +
(vA.y * vB.y) +
(vA.z * vB.z) );
vectorsMagnitude = sqrt(
(vA.x * vA.x) +
(vA.y * vA.y) +
(vA.z * vA.z)
)
*
sqrt(
(vB.x * vB.x) +
(vB.y * vB.y) +
(vB.z * vB.z)
);
tempangle = ArcCos( dotProduct / vectorsMagnitude );
if(IsNan(tempangle) == true) tempangle = 1990.0f;
Angle = Angle + tempangle;
}
if(Angle >= (MATCH_FACTOR * (2.0f * 3.140f)) ) return true;
return false;
}
