小球做平抛运动下落

void paintBall(int x,int y,int r,CDC *pDC)
{
	int R=0,G=0,B=0;
	double w,d;
	w=r;d=w/255;
	for(; w>=0; w-=d)	 
	{
	   CPen p;
	   p.CreatePen(1,1,RGB(R,G,B));
	   pDC->SelectObject(&p);
	   pDC->Ellipse(x-w,y-w,x+w,y+w);
	   R+=10;G+=10;B+=10;  
	}
 
}
void CMyView::OnDraw(CDC* pDC)
{
	CMyDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);
	CPen c;
	c.CreatePen(1,1,RGB(255,255,255));
	for(int t=1;t<200;t=t+20)
	{
		int r=20;
	    int x,y;
		x=2*t;y=0.5*9.8*t*t/300; 
		paintBall(x,y,r,pDC);
		Sleep(300);
		pDC ->SelectObject(&c);	
		pDC->Rectangle(x-r,y-r,x+r,y+r);
	}
	// TODO: add draw code for native data here
}