Ramping is nice.

Essentially it's an outside interpolation routine controling the smoke. You can definitly smooth the motion out, but my original warning was just the genral idea that if you nodes are too small (whether node is a certain smoke density or a river segment) then you won't be able to interpolate and jerkiness ensues.

All teh same, marcos ideas seems the best! It avoids having to make constant Trace_Texture calls. Much nicer!