WorldViz User Forum  

Go Back   WorldViz User Forum > Vizard

Reply
 
Thread Tools Rate Thread Display Modes
  #1  
Old 08-30-2016, 09:43 AM
dcnieho dcnieho is offline
Member
 
Join Date: Feb 2011
Posts: 59
Optical Heading reverses

I am using a DK2+optical heading setup with two markers rigidly mounted on the DK2 at 19.5 cm distance. The markers a tracked by a PPT-X system running on PPT studio 2008. It's basically the DK2+optical heading preset.

Sometimes, even when in the best part of my tracking area, but more frequently when near the edges where not all cameras have a good view, the view suddenly rotates by 180 degrees, like my head is facing down my back. I could probably detect this programmatically and rotate it right back, but what is the correct call for this? callign _swap() of the optical heading module is probably not a good idea.

Or better yet, how to avoid this?

Thanks!
Reply With Quote
  #2  
Old 08-31-2016, 07:43 AM
Jeff Jeff is offline
WorldViz Team Member
 
Join Date: Aug 2008
Posts: 2,461
When this occurs, are the markers swapping in PPT Studio? We avoid this by using Marker ID markers but I'll see if there are other suggestions.
Reply With Quote
  #3  
Old 08-31-2016, 08:37 AM
dcnieho dcnieho is offline
Member
 
Join Date: Feb 2011
Posts: 59
Hi Jeff,

Its a bit hard to say, as when it reverses i have to pull off the hmd and run to the PPT computer which shows the history of the marker positions. But when i do so, i see that each marker's path remains smooth (no sudden jumps), so i guess it is not a changing of marker ID. Is it possible to assign specific IDs to specific markers? I am not sure what Marker ID markers are.

Perhaps a settable 180 deg head rotation is all that i need to do, let me try that as a stopgap measure.

All the best,
Dee
Reply With Quote
  #4  
Old 08-31-2016, 09:00 AM
dcnieho dcnieho is offline
Member
 
Join Date: Feb 2011
Posts: 59
Hi Jeff,

It appears that there indeed is an easy stopgap solution. when i do headLink.postEuler([180,0,0],target=viz.LINK_ORI_OP) does the trick.
headLink = vizconnect.getTracker('head_tracker').getLink()

where 'head_tracker' is the OpticalHeading module.

A possibly relevant thought. I also have the following operator on the headLink:
mirrorRotationOperator = headLink.postEuler([0,0,0], target=viz.LINK_FULL_OP)

In my setup, participants walk from one side of the room to the other. I then call mirrorRotationOperator.setEuler([180,0,0]) to rotate the room so that they don't have to walk back to the starting position. This flipping of orientation by mirrorRotationOperator happens much more often than the sudden reversals of head orientation. Also, the head orientation reversal can happen at any time. Thought I'd mention it anyway in case its relevant.

Thanks!
Dee
Reply With Quote
  #5  
Old 09-01-2016, 05:31 AM
dcnieho dcnieho is offline
Member
 
Join Date: Feb 2011
Posts: 59
hi Jeff,

I have now confirmed that the markers do not seem to swap IDs (at least, if the 'ppt_left' and 'ppt_right' always refer to the same physical marker).
I had the following code run during a run of my experiment:
Code:
def debugVizConnectOpticalHeading():
	import vizconnect, viztask
	# collect raw position and orientation info, as well as merged result
	d=viz.Data(time=viz.tick())
	while True:
		samp = [d.time] + vizconnect.getRawTracker('ppt_left').getPosition() + vizconnect.getRawTracker('ppt_right').getPosition() + vizconnect.getRawTracker('dk2').getEuler() + vizconnect.getRawTracker('head_tracker').getPosition() + vizconnect.getRawTracker('head_tracker').getEuler()
		# print samp to cmd
		d = yield viztask.waitDraw()
viztask.schedule(debugVizConnectOpticalHeading())
Looking at the results, when my head turned, all that changed was the yaw, not the position of the ppt_left and ppt_right or anything else like that. I have sent a plot of the data and the recorded data to your email.

All the best,
Dee
Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Intersense InertiaCube Vic Precision Position Tracker (PPT) 2 06-15-2009 10:36 AM


All times are GMT -7. The time now is 12:33 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright 2002-2018 WorldViz LLC