The Zoom arrows increase or decrease zoom factor.
The Scale text box shows the number of pixels on the screen per unit of model coordinates. You can enter a specific scale to control model zoom; this is handy if you have several models that you want to display at the same scale.
The Near and Far clipping sliders adjust the Z clipping planes. When the model is zoomed up, it will be clipped more for a given setting of these sliders. To reduce undesired clipping with very high zooms when there is no perspective, the near clipping plane is set three times farther out from the middle in Z when Near is at 0, and the far clipping plane is set three times farther out when Far is at 1000. If there is still clipping, you can set these planes 10 times farther out by checking Set clipping planes farther out. This is not the default because it may cause inappropriate clipping on some systems.
The Perspective slider provides for a perspective view instead of a parallel projection of the model. The slider sets the angle subtended by the near clipping plane. With perspective on, both the Near clipping and the zoom setting will affect the size of the model. The near clipping plane is not moved any farther from the model when Near is at 0, but the far clipping plane is moved farther back when it Far is at 1000, as described above.
The Z-scale slider adjusts the scale for section thickness relative to the pixel size in X and Y.
The Rotation box edits model rotation. The X, Y or Z axis arrow buttons are equivalent to the hot keys on the numeric keypad. In addition, you can type specific angles into the text boxes.
If you press the Start/Stop Rotation button then one of the arrow buttons, the model will start rotating around the given axis until you press the Start/Stop Rotation button again. Otherwise, each arrow will cause a single step around the given axis.
The Link to top Slicer angles checkbox can be used to synchronize the rotation angles of the Model View window and the top (most recently active) Slicer window. When you change angles in a Slicer, the model will rotate in Model View. When you rotate the model, the top Slicer angles will be changed to match.
With Link centers of rotation checked also, the Slicer will effectively rotate around the same point as the model does (at the middle of the Model View window). This will change the point displayed in the center of the Slicer and generally change the current Z value displayed in other windows. This option is the default because it allows the Slicer view to roll around on the surface of a cylindrical or spherical object. Without the option checked, Slicer angles will change but the same point will stay in the center of the Slicer window.
The speed controls allow you adjust the rate of rotation in degrees per second (deg/sec). Press the arrow buttons to increase or decrease the speed, or enter a specific value in the text box.
The Step slider sets the the step size for single steps with the arrows or numeric pad keys. The same step size is used when rotating an object clipping plane with Ctrl and the keypad keys.
Note that the . and , hot keys will increase both the step size and rotation speed in tandem, whereas the controls in this dialog box allow you to adjust them independently.