Mathematica: Text in Graphics3D relative to image coordinates

Question

Mathematica documentation states: "Text in three-dimensional graphics is placed at a position that corresponds to the projection of the point {x,y,z} specified. Text is drawn in front of all other objects". How do you position the text relative to the image size?

This is how it can be done in 2D:

custumLabels = Graphics[{
  Text[Style["A", Red, Bold, 18], ImageScaled[{0.025, .95}]], 
  Text[Style["B", Red, Bold, 18], ImageScaled[{0.95, .05}]]}
];
Framed[Show[
  Plot[
    Sin[x] Exp[x], {x, 0, 10},
    Frame -> True,
    PlotRangeClipping -> False,
    FrameLabel -> {"x", "y"}
  ],
  custumLabels
 ],
 FrameMargins -> 0]

Those labels will always appear in that position as long as PlotRangeClipping is set to False . The question is, how do you make those labels appear at that particular position if I switch to Graphics3D . Try it with a simple one.

Framed[Show[
  Graphics3D[{Sphere[{0, 0, 0}, 1]}]
 ],
 FrameMargins -> 0]

Answer 1

Epilog and Prolog in 3D use a scaled 2D coordinate system (for all primitives):

Graphics3D[{Sphere[]}, Epilog -> Text["abcdef", Scaled[{0.1, 0.1}]]]