[david]

this was helpfull, but I still have some interrogations:

When I use the following code:

import vizmat

my_view = viz.get(viz.MAIN_VIEWPOINT)
X = vizmat.Transform()
X.makeEuler(0,-90,0)
my_view.update(X)

I get what looks like a 90 degree pitch down (should not it be up?)

and if I use
X.makeEuler(90,0,0)
I get what looks like a roll, not a yaw

And finally when I use
X.makeEuler(0,0,90)
I get the yaw

Again, this is assuming the reference frame given in the help file:
user looking down Z axis, Y axis is up, X is on the side, but it is not consistent with what Farshizzo wrote (yaw,pitch,roll order, that I don't even get for an object, as I said before)