Trim 3d surface by line or poly features?

[DavidMedeiros]

I have a 3d density surface representing water sample data taken along a stream network.

I would like to visualize this as spikes just along the stream bed. Is there a way to take the surface I have and trim it to some linear feature (like a 10 or 20 meter river buffer), so the spikes remain but the edges are clipped or trimmed at the edge of the buffer?

I tired extracting the surface by the buffer and setting the base height to the extraction and that results in a ribbon of pixels at the Z value higher but there is no fill to the bottom of the surface (like an extrusion).

[JorgeOrellana]

what comes to mind is creating a TIN from your data and using your buffer polygon as your clip so you only get the data inside the buffer distance you provide, you can  then convert that to a raster if you need it to be a raster.

See here for the the Create TIN tool ArcGIS Help 10.1

Cheers