Is it possible to Grapple?

[LSIHouston]

We are working on a grapple intensive project and we are having major problems with marker visibility.

-We are using 12 Flex: V100R2 cameras.

-We have successfully calibrated our cameras (btw it seems to be very beneficial to calibrate the system every 4 hours or so because of camera lens distortion based on temperature)

-We have successfully configured two different skeletons and the actors can maneuver together wonderfully within our capture volume.

-We have been successful in exporting our files out of Arena and brought them into 3D Max

-This is where we are stuck:
I clearly understand that when a marker gets covered, the cameras can not pick up the covered marker.

1) Is there a way to have custom marker placement or add markers to the suit without causing erratic behavior? It seems that if I trade the back marker configuration and place them on the front, the skeletal wizard can not find the 'back markers'

2) When we have actors fake their death, one of two things happen.

a) Then legs work fine because the actor landed on his back and the upper body is broken because the back markers are covered....

b) or the upper body works fine and the legs are broken because of there are no rear-thigh markers.

c) When the actors physically touch each other, the entire skeletons will try to trade bodies or their arms will flip out and go crazy.


I saw this video from a post by rock soderstorm so I know it is possible. (jeez, if thats not a superhero alias, i dont know what is!)
http://www.youtube.com/watch?v=I8gFpNOoUnE
(I tried to embed this video here into the post, but it seems that it has been disabled).


I don't know if I am answering my own question but:

1) We are using a 34 Marker setup. The 38 marker setup seems to only focus on adding markers to the feet.

2) We probably need more cameras?

[VincentG]

You can send some sample data (skl, pts data) to support and we'll take a look at it.

Also, you can add extra markers to the skeletons. Check the following posts for more information.

http://forum.naturalpoint.com/forum/ubb ... #Post43342

http://forum.naturalpoint.com/forum/ubb ... #Post43480

[farstar]

Vincent,
I am going to be trying to capture this type of action were characters will be laying down on ground, rolling aroud and then getting up. Have you guys at natural point done this type of action? If yes how did you go about doing it?

[bsteagal]

Far_Star

That type of movement is difficult for any type of optical mocap system, because you are going to have to expect some type of marker occlusion.

I've never done it, but this is what I would try:

1.- make a platform 4 or 5 feet off the ground with something like chicken wire, mesh, rebar or fence, big enough to hold your actor and have him do the movement, the idea is to use a material that you can see through. If you had a thick glass or transparent lexan (plastic) panel, that could work too

2.- Set your lower cameras closer to the ground, where they would be able to look up thru the bottom of this platform, to see the markers.

Any way you look at it, its going to be tricky.

[ProjectPalitoy]

[quote=Bryan Steagall]Far_Star



1.- make a platform 4 or 5 feet off the ground with something like chicken wire, mesh, rebar or fence, big enough to hold your actor and have him do the movement, the idea is to use a material that you can see through. If you had a thick glass or transparent lexan (plastic) panel, that could work too

[/quote]

Mmmm. Chicken wire strong enough to hold a man? Well besides the obvious, markers will also get caught in the mesh, presenting you with more problems.

As for glass.... Well the refractive nature of glass thick enough to hold that weight would give you untold tracking errors.

Your best bet in any situation like this is to build a skeleton specifically for this type of scenario, utilizing more markers than you would normally use. Look at your action requirements on video camera and assess that way. You should also choreograph your action with the limitations of your set up foremost in your mind. It may mean you will have to reach a happy compromise but forward planning and thinking is always the best foot to set of from, especially in a production environment

[bsteagal]

ProjectPalitoy:

Well, perhaps more like a mesh.. lol... like one of those garden tables.. I'm basing this on what I've seen with productions like "Beowulf" that used these types of see thru props to solve their issues with marker occlusion.

But I agree, a skeleton built specifically would be best... and expect cleanup...

[ProjectPalitoy]

Indeed

[farstar]

When you guys speek of skeleton built specifically for laying on ground mocap what exactly do you mean? Is this skeleton built in arena software? Is this posible to do in arena?

[bsteagal]

Far_Star

Sorry, adding markers to the current configuration is what we mean. Use the posts that Vincent suggested to see how to add those. The way I see it, your biggest hurdle is going to be the waist markers, specifically the back one. Adding markers to the torso, legs and arms is relatively easy.

[farstar]

Ah Ok I understand now. I will be sure to post my results I get in the near futur. Thanks for the help on this.