Computational Geometry - Triangulation
What it means to "triangulate complex 3D objects" is not unambiguous.
Just one possible interpretation: You have a 3D polygon in space, and you
want to triangulate that. This is NP-hard:


  Barequet, Gill, Matthew Dickerson, and David Eppstein. "On triangulating three-dimensional polygons." Proceedings of the 12th Symposium on Computational Geometry. ACM, 1996. (ACM link.)



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