Ive have a raster layer of earthquake data that includes depth. I also have a DEM file. The problem is that I need to plot earthquake depth relative to the DEM file rather than sealevel in order to realistically place the focal points in ArcScene 9.3. Simply using the depth data for base heights results in earthquakes that occur in the water rather than below the sea floor. I've tried fooling with the Z unit conversion and offset, but any adjust that produces reasonable result for earthquakes beneath the ocean floor leaves earthquakes that occur under mountainous area looking too deep.
DEM (RASTER) to TIN (3D Analyst required)
Converting a raster to a TIN will not, in and of itself, produce a better surface. You need ancillary data that's compatible with, and improves, the surface definition. Typically, this data would be added to the TIN in a subsequent process.