FXyz VS callouts

"and then a 3D line from there to the 3D sphere. " No, this line segment is also a 2D line. Actually its two lines of different colors, thickness and transparency which gives the illusion of 3D shading. I have a manager which reacts to any camera position/rotation changes by computing a transform of the 3D position of the sphere to a 2D point. The line segment's start x and y are bound to that 2D point. An example of how to do that same dynamic transform but with labels is in FXyz3d: https://github.com/FXyz/FXyz/blob/master/FXyz-Samples/src/main/java/org/fxyz3d/samples/utilities/FloatingLabels.java

The CAD models are slightly simplified versions of our machining models and exported as OBJ. They are more complex and produce more artifacts than hand-crafted models, but with instance sharing it's no issue to display hundreds of actuators simultaneously. Most of the models are 1-10MB, but the Hexapod chassis at the end is an unmodified export with ~150MB. The models are loaded using the OBJ loader bundled with FXyz.

"Was this done for UI reasons or mainly to decouple the rendering?" They are decoupled ... mostly... haha. The animated callout is a modified version from the one by Carl Dea: https://github.com/carldea/callouts/tree/master I say mostly because in order to get all these things to work so smoothly and at speed and scale I have had to commit a few "sins" ;-)