Mouse Controls

Left mouse button | Rotates the view or the direct light when the 'l' key is held.
Right mouse button | Translates the view. With SHIFT held down will translate faster.
Mouse wheel | Used to zoom the view in and out. With SHIFT held down will zoom faster. With SHIFT and CTRL held down will zoom even faster.
Mouse wheel + ALT | Will scroll through the detail levels of the viewed object.

It is also possible to translate or zoom the view with only the left mouse button (or the single mouse button on the standard Mac mouse) with the following key combinations:

CTRL | Translates the view as if the right mouse button were used. SHIFT may be used to translate faster.
ALT on Windows | Zooms the view as if the mouse wheel were used. SHIFT and SHIFT+CTRL may be used to zoom faster.
Apple or Command on Mac | Zooms the view as if the mouse wheel were used. SHIFT and SHIFT+CTRL may be used to zoom faster.