UNDO/REDO (Ctrl+Z)

Reverses last action.

REDO (Shift-Crtl-Z)

Redo undone steps, up to 32 steps.

UNDO (Alt-Ctrl-Z)

Undo up to the last 32 steps.

REPEAT

MATERIAL

CAMERA MODE

PREFERENCES

PURGE UNDO HISTORY

This will purge the undo history, as stated. If you purge the history, you will not be able to UNDO changes to your model. The function is intended to reclaim memory. If you find that you are running out of memory when smoothing large models, purge the undo history after each smoothing.