Vive Tracker Matrix affected by HMD Position?

[chaaseLTH9X]

Hi all,

I'm trying to control the orientation of a texture on a material based on the angle of a Vive tracker.  The script below works well for that, but there is an unexpected behavior.  When I turn my head while wearing the HMD, the texture rotates, even if the Vive tracker is not moving.  In the attachments, img1 is looking straight-on, and img2 is with the HMD turned to the right.  Any ideas?

Thanks,

CH

import math

tracker = vrDeviceService.getVRDevice('tracker-1')
tracker.enableRay('Z')

myDial = findNode('DialNode',True)
myMatl = myDial.getMaterial()
myTex = vrFieldAccess(myMatl.fields().getFieldContainer('colorComponentData'))
myComp = vrFieldAccess(myTex.getFieldContainer('diffuseComponent'))

def adjustDial():
   myMatx = tracker.getTrackingMatrix()
   rotXangle = math.atan2(-myMatx.row(1).z(), myMatx.row(2).z())
   sinXangle = math.sin(rotXangle)
   cosXangle = math.cos(rotXangle)
   rotZangle = math.atan2(cosXangle * myMatx.row(1).x() + sinXangle * myMatx.row(2).x(), cosXangle * myMatx.row(1).y() + sinXangle * myMatx.row(2).y())
   myComp.setReal32('rotate',math.degrees(rotZangle)+90)

tracker.signal().moved.connect(adjustDial)

[CGBenner]

@chaaseLTH9X 

Hello!  Do you still need assistance with this question?

[chaaseLTH9X]

Hi Chris,

Yes, I could still use some help!

Thanks,

Charles

[CGBenner]

@michael_nikelsky @Christian_Garimberti @seiferp 

Gentlemen, do any of you have any thoughts on this question?  Thank you all in advance (I know nothing about VRED!)  🙂

[chaaseLTH9X · Accepted solution]

I stumbled on the solution when looking at another forum thread.

Changing:

myMatx = tracker.getTrackingMatrix()

to:

myMatx = tracker.getNode().getWorldTransform()

Does the trick.  It turns out Vive pucks (and controllers, I think) have their tracking matrix tied to the HMD tracking matrix.