You can use Photoshop to open 3DS files, as well as other 3D formats including DAE (Collada), OBJ, U3D, and KMZ (Google Earth). Just choose File > Open and select the file. To add a 3D file as a layer in an open file, choose 3D > New Layer From 3D File and then select the 3D file. The new layer reflects the dimensions of the open file and presents the 3D model over a transparent background.