Graph3D - Double Arrow in 3rd Dimension

Question

Bug introduced in 10.0 and fixed in 11.3.0.
Graph3D is new in 10.0

---

I tried to visualize a simple graph and unexpectedly Graph3D produced a double arrow for multi-edges in the 3rd dimension:

Graph3D[
 {0,1,2,3},
 DirectedEdge@@@{{0,1},{1,0},{0,2},{2,0},{1,3},{3,1},{2,3},{3,2}},
 VertexLabels->"Name",VertexLabelStyle->White,
 VertexCoordinates->{{0,0,0},{0,0,1},{0,1,0},{0,1,1}},
 Background->Black
]

Multi-edges in the 1st and 2nd dimension are rendered correctly with two separate arrows

Graph3D[
 {0,1,2,3},
 DirectedEdge@@@{{0,1},{1,0},{0,2},{2,0},{1,3},{3,1},{2,3},{3,2}},
 VertexLabels->"Name",
 VertexCoordinates->{{0,0,0},{0,1,0},{1,0,0},{1,1,0}},
 Background->Black
]

Please help me understand this behavior. I would like my graph to have seperate arrows for all multi-edges.

Answer 1

A workaround: Use a custom EdgeShapeFunction to modify the shapes of selected edges (0->1 and 2->3) using SetProperty:

edgeShape = Module[{g = #, vs = VertexList[{#2}], p}, 
  pos = N[PropertyValue[{g, #}, VertexCoordinates]&/@vs]; 
  Cases[Show[g][[1]], ar : Arrow[Tube[BezierCurve[{p[[1]], a_, p[[2]]}]],___] :> 
  (ar/. a->({-1, 1, 1}a)), Infinity]]&;

g0 = Graph3D[{0,1,2,3}, 
 DirectedEdge @@@ {{0, 1}, {1, 0}, {0, 2}, {2, 0}, {1, 3}, {3, 1}, {2, 3}, {3, 2}},
 VertexLabels -> "Name", VertexLabelStyle -> White,
 VertexCoordinates->{{0, 0, 0}, {0, 0, 1}, {0, 1, 0}, {0, 1, 1}}, Background->Black]

Fold[Module[{es = edgeShape[##]}, 
 SetProperty[{##}, EdgeShapeFunction -> (es&)]]&, 
  g0, {DirectedEdge[1, 0], DirectedEdge[2, 3]}]