Spine still bends oddly

djtaylor · **Joined:** Fri Sep 24, 2010 12:37 pm **Posts:** 104

Greenlaw wrote:

I just noticed something very strange. This is definitely a bug but I think it's a good one--at least for now anyway.

I opened a clean, untracked project for the Shoulder Test video but this time I left Enable Shoulder Tracking disabled from start. Forward Tracking was moving along quite speedily, and when it reached the point where both arms are fully raised, this time the tracker correctly tracked both shoulders!

So, important tip for other users: if you want shoulder tracking on, leave Enable Shoulder Tracking off. At least for now. (Note: The current build as of this post is 2.2.1.145)

Just to add that I observe EXACTLY the same behaviour.

With shoulder tracking enabled, go from T pose to arms down and the right shoulder kicks up. Leave shoulder tracking off and it tracks the shoulders much better.

Greenlaw · **Posted:** Mon Feb 25, 2013 2:30 pm

Thank you for the latest update (ver. 2.3.0.146)! It sounds like this release addresses my concerns and much more. :)

Coincidentally, I recorded a lot of mocap this morning. Looking forward to using the new update this afternoon.

G.

Greenlaw · **Posted:** Mon Feb 25, 2013 11:59 pm

After working with the new build for a few hours, I'm finding there are still occasional problems with the spine. Here's an example tracked with Stiff Lower Spine enabled:

Attachment:

2013-02-25_224819.jpg [ 33.99 KiB | Viewed 17363 times ]

What's interesting is that the point cloud appears to be leaning a little to the the figure's left even though I am pretty sure I was standing straight up. My suspicion is that the shape is being distorted somehow and made to lean to the left slightly. Tomorrow I'm going to try a few experiments with different camera positions and see if I can improve the figure symmetry.

To be certain I'm not actually leaning to the left, I will set up a separate video recorder and record head-on while capturing with the two Kinects.

For tonight, I'll try different settings in Mocap Studio and see if I can improve this in tracking.

G.

Greenlaw · **Posted:** Tue Feb 26, 2013 12:06 am

Here's something else that's interesting. If I set Trajectory Filter to 0, the figure's spine straightens up.

Attachment:

2013-02-25_230141.jpg [ 33.9 KiB | Viewed 17363 times ]

The Actor is still leaning slightly to its left and that's because the point cloud is distorted/skewed that way. But besides that, the spine has straightened out with this setting. And when I switch Trajectory Filter back to 1, the spine curves sideways again. (As in the previously posted image.)

G.

Greenlaw · **Posted:** Tue Feb 26, 2013 12:09 am

Ah! It's Head Tracking! When I disable Head Tracking, the spine straightens out.

That's a shame because Head Tracking otherwise seems to work well. Would it be possible to have Head Tracking not affect the spine so much or at all?

I still don't know what's causing the point cloud distortion. I have some ideas I want to try but I will work on that problem tomorrow.

G.

Greenlaw · **Posted:** Tue Feb 26, 2013 12:18 am

No. Actually, it may have more to do with Ground Collision. If I disable Enable Ground Collision but leave Head Tracking enabled, the spine also straightens up--in fact, it looks much better this way.

I'm going to re-track this scene with Enable Ground Collision switched off and with Head Tracking enabled and see how it looks.

G.

Greenlaw · **Posted:** Tue Feb 26, 2013 12:22 am

Yes, the point cloud is definitely leaning to the left. When I disable Enable Ground Collision, the left foot sinks well below ground level. I'm guessing this must be a calibration problem. The ground plane may be horizontally level but the orientation of the point cloud is apparently rotated off-level slightly.

Attachment:

2013-02-25_232753.jpg [ 31.53 KiB | Viewed 17362 times ]

I'll record completely new tests tomorrow to see if this error is repeatable. Maybe try switching position of Kinects to see if this make the figure lean to the right.

G.

Greenlaw · **Posted:** Tue Feb 26, 2013 12:57 am

Looking at the setup I used today, I'm wondering if the point cloud distortion is due to user error--I was using the 90 degree configuration but on closer examination of the scene, my two Kinect sensors may actually have been positioned slightly wider than 90 degrees, which I believe is 'out-of-bounds' for proper calibration. (The suggested range for this configuration is between 60 and 90 degrees.)

Attachment:

2013-02-26_000143.jpg [ 51.97 KiB | Viewed 17360 times ]

That's what I get for trying to rush things. :)

Tomorrow, I'll try testing with a narrower angle and also with the near 180 degree configuration.

G.

andrew · **Joined:** Wed Apr 07, 2010 4:33 am **Posts:** 468

The latest versions of iPi Mocap Studio become more dependent on actors height. It is more important to have correct value of ground to the shoulders height rather than full height of actor. As a result in many cases it is desirable to set height of actor slightly less than actual one. For example, you can try to process your projects with 1.63 m height.

Also you can try to recalibrate with the latest version. It has some minor improvements which can slightly help.

Greenlaw · **Posted:** Tue Feb 26, 2013 8:24 am

Hi Andrew,

Thanks for the info about height. I did try both taller and shorter but at least this tells me what I should be looking at (fitting at shoulder.)

And thank you very much for getting another build out so quickly. I will focus my time today working with and report what I find. :)

G.

Spine still bends oddly

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