(Apologies in advance. My math skills and powers of description seem to have left me for the moment) Imagine a cube on screen with a two sets of controls. One set of controls to rotate the cube side to side (aka yaw or Y or even Z depending on one's mathematical leanings) and another set of controls to rotate up and down (aka pitch or X).
What I would like to do is make it so that the two set sof controls always rotate the cube in relation to the viewer / screen irrespective of how the cube is currently rotated.
A regular combination of either matrix or quaternion based rotations doesn't achieve this effect because the rotations get applied in a serial fashion (with each rotation "starting" from where the previous one left off).
e.g. With the psuedo code of
combinatedRotation = RotateYaw(90) * RotatePitch(45)
will give me a cube that appears to be "rolling" to one side because the Pitch rotation has been rotated as well.
(or for a more dramatic example RotateYaw(180) * RotatePitch(45) will produce a cube where it appears the the pitch is working in reverse to the screen)
Can somebody either point me to or supply the correct way to make the two rotations independant from each other in effect so that irrespective of how the cube is currently rotated Yaw and Pitch work "as expected" in relation to the on screen controls?