ugsplatform visualiser: only 2 deg of freedom

[J-Dunn]

The visualiser in ugsplatform is an improvement on the old UGS one. That's great. However, only being able to turn it in about two axes is limiting.

The mouse x any y coords seem to translate into movement about two axes only. The most trivial decoding of these two inputs. ie I seem to have pitch and roll but no yaw.

It should be possible to use the value of X when moving Y to provide yaw. Moving Y whilst keeping X around middle screen would pitch as at present, while scrolling Y with X near left of screen adds yaw. Opposite yaw when X on RHS.

Alternatively it could done in two axes as long as this is user's point-of-view. ie if Y scrolling always rotates about the current viewing horizontal axis rather than a fixed cartesian axis, irrespective of what the viewer is seeing. That way I could rotate one axis 90 deg then release and do a new rotation now from a new point.