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 Post subject: camera positions
PostPosted: Sat Jul 10, 2010 10:00 am 

Joined: Sat Jun 26, 2010 7:54 am
Posts: 5
Hi,

I've spent great effort in calibrating my system but I still don't seem to get a really fabulous (green) solve. Is there a tutorial available on how to position cameras precisely?

Thanks


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 Post subject: Re: camera positions
PostPosted: Sun Jul 11, 2010 6:19 am 

Joined: Sat Aug 08, 2009 4:08 pm
Posts: 91
Location: Los Angeles
There are two schools of thought on this.

One is a full circle and the other is a half circle.

Also, elevation may play a factor and it has been said that elevating the cameras to a slight downward angle improves capture results.

Then there is the settings of the camera itself which has been discussed thoroughly in the Camera Forum.

Environment can play a role so its best to keep contrast maximized. I've seen the demo where the guy is walking in an office and the motion is captured. Its probably better to have a clear view with only the floor, walls, and actor.


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 Post subject: Re: camera positions
PostPosted: Sun Jul 11, 2010 4:30 pm 

Joined: Sat Jun 26, 2010 7:54 am
Posts: 5
Thanks Infocentral,

I seem to have better results with a half circle with 1 camera at approx 2 meters height, another with 0.8 meters in height and the others at approx. 1.6 meters in height. I also noticed that keeping the actors hands stretched at all times seems to improve capture. However my capture is by far not as accurate as marker based tracking yet.


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 Post subject: Re: camera positions
PostPosted: Sun Jul 11, 2010 10:30 pm 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2352
Location: Los Angeles
The setup I've been using lately seems to work very well for me: It's a half-circle arrangement, with the cameras about 2 to 3 meters up, and far back enough to see the full figure of the performer with plenty of space around him. I have to check, but I think the cameras are between 3 to 4 meters from the performer, which is about as far as I can place them in my current shoot space. (I wish I could put them back farther.)

Also, if you're using the PS3 Eye camera, make sure you have the lens set to the wide setting. (I think it's towards the blue dot, but you can check this in Recorder.) Setting the lens to wide gives your performer more space to act in. Don't worry about lens distortion, it's not a problem with this camera and DMC.

When shooting the calibration video, try to keep the Maglite in view for all cameras for the entire duration of the video. This is easy to do in a half-circle camera arrangement, and very difficult in a full-circle because at some point you're body will probably occlude the light. IMO, this is a good argument for sticking with the half-circle arrangement. The half circle arrangement also makes it easier to manage the background, as it is much easier to clear half a room than a whole room.

You can see what my current setup is by looking at this video: iPi Studio Motion Capture Test: Sword Prop

I'm using a solid chromakey backdrop and floor tiles here, but a green screen environment is NOT actually necessary for good tracking in DMC. What's important is to have an uncluttered background to help the software matte out and isolate the performer from. Plain walls and simple furniture should be fine, but glass windows and highly reflective picture frames on the walls are not. The more complicated the background is, the more difficult it becomes for iPi DMC to see the performer's limbs clearly.

It's also important to have a clean plate in the first 30 frames of the project; I believe this is how iPi DMC mattes out the background. If you don't have a clean plate at the beginning of your video, you can drag the range to a section of the video that does. (I'm hoping that a future version of iPi DMC will let you load the clean plate video separately so you don't have to worry about setting this feature for every new video clip.)

Finally, when setting your T-Pose, make sure you alternate between Refit Pose and Analyze Actor Appearance several times. This apparently helps DMC optimize the rig and improve its matchmoving ability. Don't forget to save your Actor and Project before clicking the Track button.

When tracking is done, review the motion by clicking Play. If it's a little jittery (and it probably will be,) click the Jitter Removal button. This post process seems to very work well, especially for the feet. Remember to save your project.

Hope this helps.

Greenlaw

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Greenlaw
Artist/Partner - Little Green Dog | Demo Reel (2017) | Demo Reel (2015) | Demo Reel (2013)

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Watch a one minute excerpt on Vimeo now!


Last edited by Greenlaw on Wed Jul 14, 2010 11:31 pm, edited 1 time in total.

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 Post subject: Re: camera positions
PostPosted: Wed Jul 14, 2010 5:54 pm 

Joined: Sat Jun 26, 2010 7:54 am
Posts: 5
Thanks Greenlaw,

Your Sword Prop video is quite impressive. It proves an accurate tracking overall.
While I am getting a 99% accurate tracking on feet, hip and torso, the hand and arm tracking is still lacking. This may be down to background clutter and skin coloured furniture. Your footage capture environment and lighting is very clean and organised. I will take your advice and move capture to a controlled environment.


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 Post subject: Re: camera positions
PostPosted: Thu Jul 15, 2010 12:15 am 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2352
Location: Los Angeles
Glad to help! I've been testing iPi Studio off and on for about a year now, and it's taken me a while to figure out what works best with it. But I'm sure there's more to learn and discover yet. :)

_________________
Greenlaw
Artist/Partner - Little Green Dog | Demo Reel (2017) | Demo Reel (2015) | Demo Reel (2013)

Image
Watch a one minute excerpt on Vimeo now!


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