Joined: May 12, 2013
Post Count: 1545
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Re: *.stl
Not sure what you mean by letters, but .stl files (like the ones used for 3D printing), do not open directly in SH3D.
To convert them (to .obj format), you can use 3D modelling software like Blender. The 3D software included in Win 10 (3D modeller or something) will also let you import .stl and export .obj.