求一计算机图形学VB编程代码,用Weiler-Atherton算法,随便一个例子就可以

const int MAXVERT = 500;
const int MAXPOLYV = 50;
const int MAXH = 10;

struct Point2D
{float x,y;
};
typedef Point2D Vertices[MAXVERT];

enum VerType = {Polygon, Intersection};

typedef struct ClipListRec * ClipPtr;
struct ClipListRec
{ int Vindex;
ClipPtr next;
VerType Kind;
float t;
ClipPtr otherList;
}

struct Polygon
{ int nVertex;
int vert[MAXPOLYV];
ClipPtr list;
}
struct GenPolygon
{ Polygon exterior;
int numHoles;
Polygon Holes[MAXH];
}

GenPolygon Sub,Clip;
int entering[MAXVERT],exiting[MAXVERT];
Vertices V;
int numVertex = 0; // size of the array of verticies
int clipPoly[MAXVERT]; // a clip polygon

int readPoint();
{ cin >> inX; cin >> inY;
if (numVertex < MAXVERT)
{ V[numVertex].x = inX;
V[numVertex].y = inY;
idNo = numVertex;
numVertex++;
}
else
idNo = -1;
return idNo;
}

void readPolygon (GenPolygon p)
{ cin >> p.exterior.nVertex;
for (i = 0; i < p.exterior.nVertex; i++)
{ newId = readPoint();
if (newId < 0)
error
else
{ insertAtRear (p.exterior.list,newId);
p.exterior.vert[i] = newId;
}
}
// now do the holes basically the same way
. . .
}
// the "main" program loop would then be (pseudocode)
while (!EMPTY(entering))
{ nextInter = delete (entering);
SEARCH (SubjectPolygon,nextInter,ptr1);
AddToOutputList (ptr1->. . .)
StartPoint = ptr1->. . .
ptr1 = prt1->next;
while (ptr1->. . . != StartPoint)
{ AddToOutputList (ptr1->. . .);
if (ptr1-> . . == INTERSECTION)
ptr1 = prt1->otherList->next;
else
ptr1 = ptr1->next;
}
FixListForOutput();
DrawPolygon();
EmptyOutputList();
}