I have been thinking of a controller like this, which would be pretty fun to use for space games.
The ellipsoid marked as "Hand Piece", is supposed to be braced to the frame with motion encoders and need to push back the Hand Piece to the 0 position in case the user stops adding force in any direction.
Additionally, the hand piece can also have 5 buttons, 2 placed for the thumb and 3 placed for the 3 longer fingers each, with the button for the middle finger being a scroll wheel.
This should make up for actions like, Primary and Secondary fire, Target lock and cruise control adjustment, hence freeing the second hand for controlling utilities on the keyboard, or eating snacks. Whichever you prefer.
You are right:
The placement of the buttons will have to be decided after the shape of the ellipsoid is finalised, considering ergonomics.
Have you considered a Space Mouse? They're a little pricey, but should actually give you almost everything you want.
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