Here is the quick guide on how to triangulate in Blender:

• Import your OBJ model from the File | Import menu

• Press A to unselect all objects in the scene

• Right click on the model to select it

• Press TAB to go in edit mode

• Press Ctrl-F to call the Face menu

• Select Triangulate Faces

• Done!

• Press TAB again to finish edit mode

• Use File | Export to export your triangulated OBJ

Hope this helps.

Paolo

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