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Sketchy tracking with the Unity plugin

January 8, 2013 - 2:56pm #1

 

Hi there,
 
I'm working on an app using the Qualcom Vuforia library, and I've had a couple of snags.  I've used the v1 and v2 libraries in Unity 3 and 4 and have found the following issues.  I'm not sure if this is something I'm doing wrong, or just standard issues with AR.
 
First of all, the library is great.  It works really well and is pretty straightforward to use/extend.  I found, however, that the base version really needs the added damping code that can be found on the forum.  In fact, my client and I weren't happy with the way that that code smoothed things out, so I created my own method, which I'd be happy to share.  Either way, once the damping is added, the solution works really well 95% of the time.
 
Our particular implementation involves using a 3D depth-based mask to mask out the 3D scene where the tracker object should be, to give the appearance that the tracker object is actually in the 3D scene.  This obviously puts really heavy demands on the ability to precisely match the position of the tracker in the scene.  The damping actually is a detriment here because while it is "catching up," the mask doesn't exactly overlap the real-world object, and the illusion is broken. Also, the trackers are mounted on the front of the object, not the top.  Some are at an angle, some are vertical.  I've found that we have more issues with the vertically-mounted trackers, even when looking at them dead-on.  Either way, it was exceedingly difficult to size/position the scene/tracker so that the two objects matched up perfectly.  I'm rather confident at this point that our mask model is correct.  It seems that every time you track an object, some different offset is introduced, which we can't account for with a statically-placed scene.
 
Aside from that issue, we've found that in certain orientations, the library will spit out transformations that "flip" the scene along an axis, not by 90 degrees but by some half angle.  The scene keeps tracking this way until a different angle is reached and it flips back.  Likewise, there is a lot of "noise" when holding the camera more-or-less in the same location, which seems to essentially pop back and forth between two rotations.
 
I was wondering if anyone else has run into these issues or if there is something I'm doing differently.
 
Thanks!

Sketchy tracking with the Unity plugin

August 13, 2014 - 5:48am #16

Sorry, I have nothing at hand.  The project I was using multi-tracker for was not mine to own. I'm pretty sure the documentation explains multi-tracker setup quite well.  I didn't have any problems giving it a try.  The main challenge, IMO, is setting up the box with the trackers in real life.

Sketchy tracking with the Unity plugin

August 13, 2014 - 12:15am #15

Hmmm, thanks I will look into it, but in the meantime do you have any demo implemented with multi-tracker detection .. It will be great help.

Sketchy tracking with the Unity plugin

August 12, 2014 - 10:28am #14

Hm.  It's been a while since I've worked with the library, so my info might be out of date.  Does the tracker creation software still give you a "rating" for your tracker image?  IIRC, it will point out what features are being tracked and tell you whether you have a "bad, good, or excellent" image for tracking.  Also, if the image is large, but the tracker is still small in real life, you're still going to get tracking errors.  What really matters (I think) is the resolution of the image captured by the camera.  Another way of putting it is: "how much of the camera feed is taken up by tracker stuff?"

When I had these issues the only thing I could really do to improve the tracking was to implement a multi-tracker, which tracks images on more than one face of a cube, rather than a flat surface.

Sketchy tracking with the Unity plugin

August 12, 2014 - 10:17am #13

Hi,

My tracker image size is around 1900 x 1200, with alot of trackable objects for camera to detect.

Sketchy tracking with the Unity plugin

August 12, 2014 - 6:25am #12

Hi there,

From what I understand with tracker size, the bigger the better. How detailed is your tracker image? The more features that the camera can identify, the better the tracking.

Jittering issue

August 11, 2014 - 11:59pm #11

Hi there,

I am making a project using this awesum unity vuforia library, it is working great on the smaller image targets provided by vuforia,

But it starts jerking once I use the Big Images of those Image Targets ?? How should i tackle this issue ? Any help

 

Sketchy tracking with the Unity plugin

May 10, 2014 - 6:37pm #10

Thanks for your reaction.

Probably you're right because I'm using a fairly small tracker too. However, I cannot use a bigger tracker so I was also working on similar solutions as you suggested.

Could indeed be a (precision) math problem; some internal developer should really look into that to confirm.

 

Sketchy tracking with the Unity plugin

May 10, 2014 - 6:27pm #9

The short answer is no. It turns out that a bigger (in real life) tracker and a smaller virtual object is the only real solution.

Our setup of a small tracker (on product packaging) and a scene that opens up around it was kind of just doomed from the start.

I ended up with some heavy filtering (interpolation toward sensor values) and essentially ignoring the flipped rotations. The latter only works because we already were constraining the viewing angle. It was basically a diorama around the tracker object.

What we should have done is used a large sheet of paper on the table to provide a bit "base" for the scene instead of using a small object in the center.

The best I can come up with is that with small trackers, precision issues screw up the math causing these undesirable behaviors

Sketchy tracking with the Unity plugin

May 9, 2014 - 4:01pm #8

Hi,

I'm also experiencing the 'jittering' and the 'flipping'.

Regarding the jittering; it seems like some kind of noise but when I use a still image I got the same problem as well.

As for the flipping; I've the same problem that it's swapping between two rotations; the correct one and the one flipped by 90 degrees along the X (right) axis relative to the camera . This tends to happen more often with dark environments.

Is there a solution to those problems yet?

Sketchy tracking with the Unity plugin

February 6, 2013 - 6:24pm #7

@schoen,

Have a look at UCS. It is a replacement for MultiTargets (amongst other things) and you can place the markers in any configuration you want. I will release a version supporting Vuforia 2.0 soon.

Sketchy tracking with the Unity plugin

February 3, 2013 - 12:09pm #6

Hey there,

So... to pick up where we left off:  I'll get you some video soon.  I'm not sure I can set these objects up as multi-trackers because the real-world objects aren't cubes or cuboids.  You'll see when I send over the video.  I'll PM some youtube links.  Thanks for all your help!

Sketchy tracking with the Unity plugin

January 23, 2013 - 8:53am #5

Try bringing the targets into a MT configuration if you can. 

And post, or PM, a link to any video you have. 

Sketchy tracking with the Unity plugin

January 22, 2013 - 10:13am #4

Thanks for the reply.

The targets are not MultiTarget.  I have simultaneous targets set to 1, and there are 5 possible targets.  I can't exactly bring the model closer because the model is actually a whole scene (not my idea).

 

The scene is centered on the target, but extends out in all directions, and we tend to notice more jitter on scenese that extend farther in the Z direction (where Z is the camera axis). 

We also seem to be experiencing "flipping" issues for targets that are vertical (coplanar with the XY plane) which I assume to be Gimbal Lock issues.  I'll try to get some videos that illustrate the issues we're having, but I don't think a screen grab would do it.  I suppose you would like to see what it looks like without filtering?

Sketchy tracking with the Unity plugin

January 22, 2013 - 9:40am #3

Can you send me an example a/o some screen grabs of your project? 

Are your targets configured as a MultiTarget?

Filtering isn't generally necessary to smooth the pose estimation. If you're seeing a lot of jitter, try bringing your model closer to the origin of the target. 

Sketchy tracking with the Unity plugin

January 22, 2013 - 9:30am #2

bump

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