Using the Mouse to Navigate

The center mouse button is used as a navigation button.

Center-dragging while the mouse pointer is over an object examines the object. Center-dragging while not over an object result in zooming in/out.

Holding down the ctrl key while center-dragging results in navigation along the XZ, plane hovering over the scene.

Holding down the ctrl key while center-dragging results in navigation along the XY plane.