Options :
- press '+' (or '-') to get the camera further away from (or closer to) the origin.
- use the mouse "drag and drop" to rotate the camera around the surface
- use 'i' to create some inertia and 'Shift+i' to decrease it
- use 'f' to flatten the surface and 'Shift+f' to do the opposite
- use 'c' and 'shift+c' to change the contrast between highs and lows
A1 is the angle between the camera and XZ and A2 is the angle between the camera and XY Di is the distance to the origin.