Configuring S3d to output G-code to your OctopPrint
Using a post processing script curl can upload sliced gcode files to your Octoprint server using your API key.
Place this in the "Additional terminal commands for post processing" field at the bottom of the "scripts" tab window in "process settings".
curl -k -H "X-Api-Key:(yourapikey)" -F "select=false" -F "print=false" -F "file=@[output_filepath]" "http://(yourip)/api/files/local"
Replace (yourapikey) and (yourip) with the information for your Octoprint server.
Curl for Windows -- https://curl.haxx.se/download.html
Octoprint -- http://octoprint.org/
Simplify3d -- https://www.simplify3d.com/