How to get gravity vector?

[GoogleCodeExporter]

Hello,

I need to place the PS Eye in a high position so that it will be tilted down.
I want to keep the up vector of the Move coordinate system parallel with 
gravity, so I need to make a corrective rotation to fix the effect of the tilt. 
If I knew what the direction of gravity was, I could apply the correction. Is 
there a way to get the gravity vector, or any other means for me to 
automatically determine how many degrees the PS Eye is tilted?

Original issue reported on code.google.com by TMTak...@gmail.com on 11 Feb 2012 at 12:56

[GoogleCodeExporter]

Hi,

You can find the estimated pitch angle inside the data sent over from the 
network. But, the Move system attempts to correct for the pitch angle of the PS 
Eye automatically so it may not be necessary for you to do anything.

Original comment by j...@johnmccutchan.com on 12 Feb 2012 at 2:16

[GoogleCodeExporter]

Hi John,

Thank you for the reply. It appears that I moved the camera to the high 
position after starting Move.me, or something, as restarting the PlayStation 
seemed to work.

There seems to be three pitch angles available, which confuses me a little:

camera_pitch_angle     "Current camera pitch angle"
pitch_angle            "Camera pitch angle used for state computation"
pitch_angle_estimate   "Current camera pitch angle estimate"

What is the difference between these three?

Original comment by TMTak...@gmail.com on 18 Feb 2012 at 5:40

[GoogleCodeExporter]

Hi,

Move State:

camera_pitch_angle - The camera pitch angle that was used for computing state 
(position, orientation, etc) of the Move controller.

Camera State:

pitch_angle - Same as the above camera_pitch_angle.
pitch_angle_estimate - The current estimate for pitch angle (will be used in 
future frames).

---

Two things:

1) As I said, Move.Me attempts to estimate the pitch angle of the camera and 
updates the estimate regularly. You shouldn't have to do anything special to 
get an accurate pitch angle. From this pitch angle you should be able to 
determine the gravity vector.

2) The state of the Move controllers transmitted by Move.Me already has the 
pitch angle factored into it. You shouldn't have to do any extra processing 
here.

John

Original comment by j...@johnmccutchan.com on 27 Feb 2012 at 3:35

[GoogleCodeExporter]

Thanks for detailed explanation of the variables!

I also got your points 1) and 2). I haven't had any issues with the pitch since 
I posted my first messages here, so I probably was mistaken or did something 
wrong in the beginning.

All is clear now.

Original comment by TMTak...@gmail.com on 4 Apr 2012 at 3:02