Command entry:Click or right-click the General viewport label (“[ + ]”) . 
General viewport label menu Configure Viewport Configuration dialog Regions tab
On the Regions panel of the Viewport Configuration dialog, you specify default selection rectangle sizes for the Blowup Region, the Sub Region rendering options, and (for legacy drivers) the parameters for setting up a virtual viewport.
The rectangular selection region appears in the viewport when you choose either the Blowup or Region option from the Area To Render list. You can change the size of a region by dragging its handles, and its position by dragging anywhere within its borders.
The Virtual Viewport options let you zoom in on a sub-region of the current viewport, creating a “virtual viewport” where you can perform any standard navigation, but in a zoomed-in area. This function works only when you're using an OpenGL driver. If you're using the software or Direct3D driver, these controls are disabled.
You can use the virtual viewport on any type of viewport, but it's primarily designed for zooming in on camera views. This lets you perform close-up work, such as tracing, without distorting the relationship between the geometry and a bitmap background. (See Lock Zoom/Pan in Viewport Background for similar functionality in orthographic views.)
Because you're actually zooming the viewport image itself, the viewport label might be hidden from display, but you can still right-click in the upper-left area of the viewport to display the menu. This takes advantage of zooming features in the Open GL driver so that 3ds Max does not compute the display change internally.
Viewport Configuration and click the Regions tab.
The viewport is converted to a virtual viewport and displays the area of viewport represented by the white rectangle. All viewport navigation methods work the same, except that you're seeing only the zoomed portion of the viewport.
Region Tab and turn off virtual viewport. You can get to the Viewport configuration menu by right-clicking any of the viewport
navigation tools or by going to Views menu Viewport Configuration.
