8Cam OptiTack+ARENA Test - (Jan.8.2008)

[johnou]

Hi Tech People At NaturalPoint.

Here is few test we have that require your tech support urgently.
We've got your 8 camera system just right before x'mas and we have run more then 4 mocap test session.

There is few issue that stop us getting clean data.

Here is our image short of setup:


Here is our questions for you:

1) Are you able to let us know what went wrong with our setup? Whats the best camera heights, angles, dis between upper and lower cam. Our actor hight is 170cm avg and ideal performing stage is 5x5 meters.

2) During our test, we are try small space, but never get it right, there always a noise happening after we finish our camera calibration with the result of all excellence. Noise means on the screen appears extra tracking points rapidly appears on the space. I have already block all visible points and the exposure settinf in ARENA is "14~23".

Can you help us out here since we have to get a clean data from 8-camera system this week. If we can get a clean data out of this 8-Camera setup, we may also upgrade to 12 cam system in 3 month time.



Many Thanks.
John Ou
Head of Animation

[leith]

your setup shows what looks to be a lot of daylight light sources. daylight has a lot of IR in it. I'd probably start by trying to get the cameras higher so they can't see out of that high window. I'd try to cover up the high window if possible.

I'd try to use the camera masking to block out the rest. I'd make sure to move from my original position after the first mask capture, and capture again, to make sure my body did not block something that should be masked the first time.

noise is normal. thats what a smoothing filter is for. extra markers have a tendency to happen, but if they're rampant than you may have a falsely converging calibration (data set is too homogeneous, resulting in a solution that is not correct) or perhaps you need to increase the number of rays required to reconstruct a point. You might also just need to increase your residual.

Its hard to tell without being there to see it, or without seeing the data unfortunately.

[seanboyette]

I agree with Brad - you may try to a night capture if possible, and the height will certainly assist.

Also - while it will not assist with the stray markers - you may want to pull the 1.6 meter section apart just a bit in order to get a larger volume. Actually of them could be moved out just a bit - distance and height will assist with expanding your volume.

can you describe - or take a screen shot of each grayscale cam's view.

Sean

[johnou]

Thanks Brad and Sean, that's so true the day light cause many flickers... I will try tonight without any daylights.

ARENA Questions,

1)The upper arm issue, never get it straight when snap to the skeleton in AREAN.

Here is the graph.

[seanboyette]

John,

This could be because of your sizing of your skeleton?
Did you size it in proportion to your actress, including height and shoulder width?

It could also be the placement of that top marker - I place mine a biut higher on the shoulder.

What is your final output software?

Sean

[yoshi]

John,
For your upper arm issue, it looks like the top upper back marker is placed too high. It should be placed lower, at the same height as shoulder joints while in T-pose.

Also if you can post your .pt2 file, we can investigate what is causing the extra markers.

[Birch]

Turning on untracked-rays in the settings -> display tab can also be useful for diagnosing calibration quality and unwanted light source issues.

The red untracked rays show 2D light sources which cameras have picked up that did not get used to form 3D markers. They are usually the result of either unwanted light sources (not properly blocked) or a cameras calibration causing the ray to pass too far away (greater than residual setting) from other rays for a given 3D marker which it should have been used for.

[Jim]

To place the cameras further apart you can increase the length of the sync cables. You can just use standard RCA cables with a double female joint. Sync cables can be up to 30' long. The extra length would let the cables be strain reliefed and not swoop between tripods, which can cause movement of the cameras and therefore a bad calibration or use of the system.

It is encouraging that you can calibrate the system out and set the ground plane, that is usually the hardest part. Getting rid of the extra markers is an optical noise issue, like the sunlight in the background.

For your capture size, I would set the Exposure value at between 40 and 50 and the Illumination value at 15. Threshold should be over 150. Use the Grayscale option to preview what could be causing lighting problems.

Good luck! You are close.