Coordinate system flips when pitch crosses 90deg?
 

we realized an odd behavior in observer coordinates: When the observer moves on a continuous trajectory that curves upwards, as soon as the pitch crosses 90deg (i.e., as soon as the observer is upside-down) the observer coordinates seems to flip upside-down as well (resulting in a change in heading, pitch, and roll coordinates)...
Is that a know feature (is it documented anywhere)?
more importantly, is there a way to switch it off?

We're trying to compute hoping vectors and the whole things get's messed up currently when the coordinates have a discontinuous jump :confused:.

Thanks for any advice!

Bernie

What kind of tracking system are you using?

hey bernie...
i faced them same problem while i was trying to rotate an object 360 deg it flips on 90 deg..
i used relative rotation and it worked just fine

obj.setEuler((110,0,0),viz.REL_LOCAL)

Thanks, I'll try the relative location as soon as I get back into the lab (I don't have vizard at home). Jeff, I'm not using any tracking, just plain 3D computer graphics, and a trajectory controlled by a script. so no direct user input.
Thanks
Bernie

Do you have sample code that demonstrates the problem? This sounds like a gimbal lock issue with euler angles. Are you using euler angle to compute the trajectory?

Sorry for the delay in responding, my colleague Shawn will take over the discussion as he'll be working on the code.
we'll try to isolate the problem into a sample code. Right now we use a viz.MainView.rotate() command to update the observer's orientation each frame (viz.MainView.rotate(1,0,0,d.turnDir * d.dPhi_angle2rotateThisFrame,viz.BODY_ORI,viz.REL_ LOCAL))

I guess it could indeed be a gimble lock problem and we'll look into that.
Thanks!
Bernie

Hi
This is shawn ...
Sorry about the delay.

There is some sample code attached. It first rotates the MainView, pitch, over various angles between -175 and +175. Then it rotates a pointer object over the same range.

Using something like viz.MainView.setEuler(([0, pitchs[i], 0]),viz.REL_LOCAL) produced the same results.

The rotations over 90 degrees, under -90 degrees, pitch produce something like the following:

MainView pitch= -175 i= 0
MainView.getEuler = [-180.0, -5.0000009536743164, 180.0]
mpointer.getEuler = [2.7940182008023839e-006, 5.0000009536743164, 180.0]

MainView pitch= -150 i= 1
MainView.getEuler = [-180.0, -30.0, 180.0]
mpointer.getEuler = [3.0043981951166643e-006, 30.0, 180.0]

MainView pitch= -100 i= 2
MainView.getEuler = [-180.0, -80.0, 180.0]
mpointer.getEuler = [9.4240658654598519e-006, 80.0, -180.0]

...

mpointer.pitch= 100 i= 10
MainView.getEuler = [0.0, 0.0, 0.0]
mpointer.getEuler = [180.0, 80.0, 180.0]

mpointer.pitch= 150 i= 11
MainView.getEuler = [0.0, 0.0, 0.0]
mpointer.getEuler = [180.0, 30.0, 180.0]

mpointer.pitch= 175 i= 12
MainView.getEuler = [0.0, 0.0, 0.0]
mpointer.getEuler = [180.0, 5.0000009536743164, 180.0]