//----------------------------------------------------------------------------// CHECKS IF 2D POINT P IS IN TRIANGLE ABC. RETURNS 1 IF IN, 0 IF OUT//   Given a triangle ABC and a point P, determines if P is inside//   of ABC (regardless of vertex ordering - CCW or CW). 2D version only, but//   this handles the 3D case if appropriately projected to the XY, YZ, or XZ//   planes (by dropping corresponding component; i.e. drop Z in XY projection).//----------------------------------------------------------------------------int Pt2dInTri(Vect2d A, Vect2d B, Vect2d C, Vect2d P){	// FIRST CHECK THE SIGN OF THE Z-COMPONENT OF THE NORMAL BY CALCULATING	// THE CROSS-PRODUCT (ABxBC). THIS WILL DETERMINE THE ORDERING OF THE	// VERTICES. IF NEGATIVE, VERTICES ARE CLOCKWISE ORDER; OTHERWISE CCW.	// THEN EVALUATE SIGN OF Z-COMPONENTS FOR ABxAP, BCxBP, and CAxCP TO	// DETERMINE IF P IS IN "INSIDE" HALF-SPACE FOR EACH EDGE IN TURN ("INSIDE"	// IS DETERMINED BY SIGN OF Z OF NORMAL (VERTEX ORDERING).	// NOTE: FULL CROSS-PRODS ARE NOT REQUIRED; ONLY THE Z-COMPONENTS	Vect2d dAB=B-A, dBC=C-B;  // "REPEATS"	if ((dAB.x*dBC.y-dAB.y*dBC.x) < 0) // CW	{		if (dAB.x*(P.y-A.y) >= dAB.y*(P.x-A.x)) return(0);           // ABxAP		if (dBC.x*(P.y-B.y) >= dBC.y*(P.x-B.x)) return(0);           // BCxBP		if ((A.x-C.x)*(P.y-C.y) >= (A.y-C.y)*(P.x-C.x)) return(0); // CAxCP	}	else // CCW	{		if (dAB.x*(P.y-A.y) < dAB.y*(P.x-A.x)) return(0);           // ABxAP		if (dBC.x*(P.y-B.y) < dBC.y*(P.x-B.x)) return(0);           // BCxBP		if ((A.x-C.x)*(P.y-C.y) < (A.y-C.y)*(P.x-C.x)) return(0); // CAxCP	}	return(1); // "INSIDE" EACH EDGE''S IN-HALF-SPACE (PT P IS INSIDE TRIANGLE)	};