I have bunch of DEM. I need to do a country polygon DEM for 3D mapping. How can I get the country's polygon with DEM, the any shaped polygon DEM? I tried "intersect" tool, but it only allow two polygon to intersect, not DEM.
Extract by Polygon—Help | ArcGIS Desktop
you will still have nodata values outside the shape and within the rectangular extent of the raster as expected
Another option is to create a Mosaic Dataset for your DEM's and update the property of "Always Clip the Mosaic Dataset to its Boundary" property to Yes in the Catalog Window MDS properties after you've updated the Boundary to match the country boundary.
Retrieving data ...