OPENGL鼠标中间缩放问题

[C_码农]

滑动鼠标中间对鼠标指向的点进行缩放，在xp中放大到一定程度物体不能完全显示，在WIN7中放大图形就直接消失了

图1是原始图

图2是放大后的图，不能显示完整
求大神帮忙

[C_码农]

这幅图也是放大后的效果

[C_码农]

实现代码： BOOL CMy6TDlg::OnMouseWheel(UINT nFlags, short zDelta, CPoint pt) { CRect rect; GetWindowRect(&rect); int w = rect.Width(); int h = rect.Height(); float camFovy; if(zDelta>0) { glTranslatef(object_x,object_y,object_z); glScaled(Magnification =EnlargeX*1.2,EnlargeY*1.2,EnlargeZ*1.2); glTranslatef(-object_x,-object_y,-object_z); }else { glTranslatef(object_x,object_y,object_z); glScaled(Magnification=EnlargeX*0.5,EnlargeY*0.5,EnlargeY*0.5); glTranslatef(-object_x,-object_y,-object_z); } UpdateData(false); return CDialog::OnMouseWheel(nFlags, zDelta, pt); } void CMy6TDlg::OnMouseMove(UINT nFlags, CPoint point) { GLint viewport[4]; GLdouble modelview[16]; GLdouble projection[16]; GLfloat winX,winY,winZ; glGetDoublev(GL_MODELVIEW_MATRIX, modelview);//视图矩阵 glGetDoublev(GL_PROJECTION_MATRIX, projection);//投影矩阵 glGetIntegerv(GL_VIEWPORT, viewport);//视口 winX=(float)point.x;//OGL中的窗口x坐标 winY=(float)viewport[3]-(float)point.y;//OGL中的窗口y坐标 glReadPixels(point.x,//x坐标 int(winY), 1,1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ); gluUnProject((GLdouble)winX,(GLdouble)winY,(GLdouble)winZ,modelview,projection,viewport,&object_x,&object_y,&object_z); }