Cannot 3D print prisms and ellipsoids

Question

I get errors if I try to Printout3D[ ] or Export[ ] to an .stl file an object containing either an ellipsoid or prisms with any complexity. For example, neither:

testError = Graphics3D[{Tube[{{0, 0, 0}, {1, 1, 1}}, .1], 
  Ellipsoid[{1, 1, .5}, {1, 1, .1}]}]

... nor

pos=20; top=.9; bottom=.1
testError=Graphics3D[
  Table[Prism[{{0, 0, top}, {1.2 Cos@x, 1.2 Sin@x,top},
 {1.2 Cos[x + 2 Pi/pos], 1.2 Sin[x + 2 Pi/pos], top}, {0, 0, bottom}, {1.2 Cos@x, 1.2 Sin@x,bottom}, {1.2 Cos[x + 2 Pi/pos], 1.2 Sin[x + 2 Pi/pos],bottom}}],
 {x, 0, 2 \[Pi] - 2 \[Pi]/pos, 5 2 \[Pi]/pos}]]

... produce the expected results with either Export["test.stl",testError] or Pintout3D[testError,"test.stl"]. What am I doing wrong? Using 12.1.

Answer 1

Just as @flinty mention,here we using DiscretizeGraphics and increasing the MaxCellMeasure for nonlinear model such Tube and BezierSurface.

mesh1 = DiscretizeGraphics[
  Graphics3D[Tube[{{0, 0, 0}, {1, 1, 1}}, .1]], 
  MaxCellMeasure -> {"Length" -> 0.01}]
mesh2 = 
  DiscretizeGraphics@Graphics3D[Ellipsoid[{1, 1, .5}, {1, 1, .1}]]
RegionUnion[mesh1, mesh2]
Export["combine.stl", %]
Import["combine.stl"]