Hi,
By default the volume viewer (in Live or regular Csparc) allows users to threshold volumes at all values present in the map.
This means that if users drag the threshold to the left, they will see a cube, and the user has to look carefully for what point on the threshold slider corresponds to 0.
I think generally negative thresholds are not useful in this context. Perhaps it would be worth restricting thresholds to positive values? This way all allowed thresholds would be somewhat informative.
Cheers
Oli