Add new file for tgview3d system

systems/tgview3d.md

+---
+layout: system
+
+menu_title: TGView3D
+shorttitle: TGView3D
+title: The TGView3D Graph Viewer
+teaser: An interactive 3D graph viewer optimized for visualizing Theory Graphs and mathematical knowledge in general
+
+start_date: '2018'
+
+people: 
+    - mkohlhase
+    - frabe
+    - dmueller
+    - rmarcus
+
+
+supported-by:
+    - odk
+
+website: https://tgview3d.mathhub.info/
+repository: https://github.com/UniFormal/tgview3d
+publink: https://kwarc.info/people/mkohlhase/submit/cicm20-tgview3D.pdf
+---
+The TGView3D System is a 3D-theory graph viewer in the Unity Engine.
+Different layouts and highlighting settings are available to visualize the complex theory graphs efficiently.
+In particular, this allows exploration of big mathematical libraries, e.g, those related to theorem provers like Coq or Isabelle.
+Furthermore, we have a virtual reality protoype to allow intuitive and immersive interactions.
+
+
+*For students*: Topics for theses and projects are available [here](https://gl.kwarc.info/kwarc/thesis-projects/-/issues?label_name%5B%5D=Graph+Visualization).
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