OpenGL中的鼠标控制

昨天在《OpenGL中的光照和键盘控制》中的代码的基础上加入了用鼠标来控制旋转，不过自己觉得思路是不正确的，纯属瞎弄。。。

为了识别出用户想要旋转的方向和角度，增加了下面的变量：

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> enum RotateDirection
{ // 鼠标控制的旋转方向
EAST,
WEST,
NORTH,
SOUTH
};

RotateDirectiondirection;
CPointm_pStart; // 起点
CPointm_pEnd; // 终点
bool isMoseDown; // 是否左键还按下

然后就是鼠标的事件处理代码了：

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> void COpenGLDemoView::OnLButtonDown(UINTnFlags,CPointpoint)
{
// TODO:Addyourmessagehandlercodehereand/orcalldefault
this -> isMoseDown = TRUE;
this -> m_pStart = point;
this -> m_pEnd = point;
CView::OnLButtonDown(nFlags,point);
}

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> void COpenGLDemoView::OnLButtonUp(UINTnFlags,CPointpoint)
{
// TODO:Addyourmessagehandlercodehereand/orcalldefault
this -> isMoseDown = FALSE;
if ( this -> direction == EAST)
yspeed += 0.5f ;
else if ( this -> direction == WEST)
yspeed -= 0.5f ;
else if ( this -> direction == SOUTH)
xspeed += 0.5f ;
else if ( this -> direction == NORTH)
xspeed -= 0.5f ;
CView::OnLButtonUp(nFlags,point);
}

void COpenGLDemoView::OnMouseMove(UINTnFlags,CPointpoint)
{
// TODO:Addyourmessagehandlercodehereand/orcalldefault
if ( this -> isMoseDown == false )
{
return ;
}
if (point.x > this -> m_pEnd.x)
this -> direction = EAST;
else if (point.x < this -> m_pEnd.x)
this -> direction = WEST;
else if (point.y > this -> m_pEnd.y)
this -> direction = SOUTH;
else if (point.y < this -> m_pEnd.y)
this -> direction = NORTH;

this -> m_pEnd = point;

CView::OnMouseMove(nFlags,point);
}

试了下效果，控制上不是很舒适方便，我觉得自己才旋转的方向判断上应该是不对的，到底如何判断旋转方向呢？