3次B样条曲线

void B3_Line(CDC *pDC,CPoint p1,CPoint p2,CPoint p3,CPoint p4)
{
	int x0=p1.x,y0=p1.y;
	int x1=p2.x,y1=p2.y;
	int x2=p3.x,y2=p3.y;
	int x3=p4.x,y3=p4.y;
	float i,t,t3,t2,n=1000;
	i=1/n;
	const	float f=float(1.0/6);
	float px,py;
	px=x0;
	py=y0;
	for(t=i;t<=1;t+=i)
	{
		t3=t*t*t;
		t2=t*t;
		pDC->SetPixel(int(px+0.5),int(py+0.5),RGB(0,0,0));
		px=f*((-t3+3*t2-3*t+1)*x0+(3*t3-6*t2+4)*x1+(-3*t3+3*t2+3*t+1)*x2+t3*x3);
		py=f*((-t3+3*t2-3*t+1)*y0+(3*t3-6*t2+4)*y1+(-3*t3+3*t2+3*t+1)*y2+t3*y3);
	}
}