3 actor support?

[Pixerati]

For my needs, 3 simultaneous actors is the sweet spot. So:

1. Is the 2 actor limit currently just a software limitation?

2. If so, could I get around the limitation by adding a third actor, selecting all the markers for that actor, creating a 34 marker rigid body in Arena, then assign those markers to a third actor in MotionBuilder?

3. If not (2.), then could I set up a 2nd Optitrack system in the same performance space as the first, and track the third actor there?

Thanks.

[Pixerati]

Oh, and before anyone says anything, yes, I know the 34 markers would not be a true rigid body. I'm merely suggesting assigning them to one to get them into MotionBuilder.

[Jim]

Hello:

There is no hard limit on how many skeletons you can have active at one time, so maybe 3 would work. We have not tested that here yet.

You would need a very fast Quad Core machine to try this out. Also, we recommend no more than 18 cameras at one time. Finally, you need to have unique root bone marker configurations for the 3 actors, meaning the back waist marker needs to be in a unique position.

You might also try just capturing the point cloud in real time, and then turning on the skeletons in play back as you trajectorize the data. This can reduce your CPU load and may help make a better capture.

Give it a try and let us know, you would be doing it before we can get to testing it, so you are leading the way!

[Pixerati]

Thanks. I'm on a quad 2.66 machine right now, but I might try switching to one of my 8 core Mac Pros running XP if I need it.

By the way, any diagrams for configuration/layout of 18 cameras yet?

Thanks.

[Birch]

Yeah, there are now 18 and 24 camera diagrams here :

https://www.naturalpoint.com/optitrack/ ... n-capture/

[Jim]

The Quad core should do it. I think we will try and test this next week, with the same spec machine. Maybe you will beat us to it.

[dtaylor112]

What is the required set up for a 2 actor set up (I wasn't 100% sure optitrack supported 2 actors now!)

I'm getting the 8 camera setup. I have a dual core 2.5 ghz laptop (windows XP) with 2 gigs of RAM (I also have a quad core but it's a desktop)

Would the laptop and the 8 camera setup be enough?

Also, would I only need to get another mocap suit? If so, how many markers should be on each?

Thank You

[Jim]

Hello:

Yes, ARENA does support 2 actors.

8 cameras could work, but we recommend 12 cameras for good coverage with 2 actors.

There is nothing bad about just trying it with 8 cameras, it could work well for the type of moves you want to do, worth trying it for sure.

The laptop should be fine, but if it is too slow, the Quad should handle it with ease.

Yes, just one more suit is fine. You will run the same default marker setup, 34 markers each. The only difference is the placement of the back root marker (the one on the lower waist line), for one actor, put it to the left, for the other, put it towards the right. The default is in the center. This will help ARENA determine the correct actor.

You simply create another skeleton, load it, and it will track two people really nicely. We have been doing body hugs and all kinds of interaction and have been quite pleased with the results.