Match Moving

[gman]

I have recently purchased a cheap sanyo xacti HD camcorder to try a mix some CG with recorded footage. I have been reading various tutorials and was wondering if anyone knew of a good softimage specific match moving tutorials. I have read that I probably will need to process the footage with something like Foundry Rolling Shutter, does anyone know if this is a must? Do I have any other options? How do you work out the focal length?

I'm thinking of using Pixel Farm PHhoe to do the tracking as this is not to expensive, then export the camera into XSI.

Any help would be great.

Cheers

G

[Rork]

Hi,

Lots of questions with no quick answer ;-)

First of all, I would recommend buying Tim Dobbert's book:
http://www.amazon.com/Matchmoving-Invis ... 249&sr=1-1
It's the one and only and definitive book on tracking.

Second, there are no real SI related tracking videos. You have the basic tuts on a tracking app (e.g. on Gnomon), and all 3D apps have their own way of importing the tracked data. Most of that is normally described in the tracker's manual.

Thirdly, I don't knowe that camera but stay away from any interlaced footage. For tracking it's b.a.d. DV video is even w.o.r.s.e.
I didn't know PFHoe was still being sold, I can remember it was discontinued some time ago. Now with PFMatch etc. coming out they're concentrating on other fields.
For 'cheap' tracking SynthEyes is very good.
People who are lucky enough to be on maintenance get the old Matchmover, but because that is more or less EOL I wouldn't recommend investing any time in it. If you want to use apps like this on a professional level and maybe to get a job, move towards SynthEyes or PFMatch/Track.

But to answer on some of your questions on a global level:

- chip-size/aspect ratio(filmback) and focal length are interrelated. There should be a value mentioned of the chipsize, and 35mm eq. lensvalues in the manual of the camera. Convert this from inches to mm or vice versa to fill in those values in the tracker app. Also this will help a lot for the tracker software to figure out what's going on. If you don't know a focal length at least set the filmback to the proper values and have the software figure something out.
SynthEyes has a clever tool to do some of this manually.
The 'rolling shutter' issue is one found when shooting with a lot of DSLR's, in your case it's finding out if this issue occurs while filming.
There are some other issues that come to mind when looking at your footage, like lens distorting, stabilization, and if you want to address that before or after tracking.

Also getting a good solution depends on a lot of factors, and having a solution that looks good before exporting, can still have issues with drifting models after importing it into the 3D app.
A lot of this stuff will take some experience to deal with.

Just start shooting short tests, post them here and we will have a small 'how to' based on your experiences.

rob

[gman]

Thanks for the reply Rork. Pfhoe is still for sale : http://www.pfhoe.com/products.php . I looked at SynthEyes but that is much more expensive.
I have just ordered a new SD card, so when that arrives I think I will create some short shots and post them here as suggested. I think I will start with a basic table shot and place a simple object onto the table. Hopefully the footage is not interlaced as you mentioned. I try and find out.

Thanks again Rork.

G

[gman]

I just found out the recording would be Interlaced, so does that mean it will be much harder? or impossible?
MP4

[Rork]

Hi G,

Not impossible, but most of the time harder due to the fact you normally pick one of the fields (and getting half of the resolution) and the bad compression these (DV) camera's bring to the table.
I still don't get it why HD was approved for interlaced recording. "Standards are nice, just pick one".....
I usually work with frame sequences, highres ones for the track, lowres for the rotoscope.

I've looked into the PFHoe vids a bit as I had some time, and for the money it's a nice starter deal. It looks a lot like it's big brothers PFTrack and PFMatch.

Looking at PFHoe Pro and SynthEyes, I would still recommend SynthEyes as you have much more control over your software. I know it's over twice as expensive as Pro, but that would pay itself back very quickly if you struggle with a shot for a day.
Trust me, I know... And I used Maya Live, Matchmover, Boujou, PFTrack and SynthEyes. ;)
But I have to admit as well that 'stepping up' will introduce a much steeper learning curve.

I do like the starter approach PFHoe takes with it's step-through-the-buttons approach, and the Pro version has manual trackers as well. I do miss some very helpful features, like the ability to assign tracked sets of points to planes so the track can be resolved, the ability to have keyframe/link manual tracks when they are obscured by objects for a couple of frames. Or the ability to merge several solves from the same scene. And the ability to create masks from within the app is a must. It's very tedious to go back and forth to add another mask when you need it. Also there's no way to set known values for lens and filmback. It will assume some of it from the footage, but this could be wrong when cropping is involved. But you get what you pay for. ;)

Some quick tips on tracking:
- mask out any moving objects in the scene as it will confuse the software and will result in a bad track.
- mask out obvious patterns that will create moving grids as it will confuse the software, e.g. lamppost in front of horizontal wooden fence. You can also delete these kind of tracking errors after the track finished and before the solve
- look for any strong reflections and highlights on objects, they can throw off the solve later on as these tend to shift based on the shape of the object.
- have at least some parallax in your scene. No parallax will not get you a solve as the software depends on it. Exception to this is a nodal pan as the camera is locked on it's position. This will result in a solve that will look like it's spherical. It will not have any real depth to it.
- set up a logical coordinate system after the solve, as it will help you greatly when you start doing the 3D.
- if you distort the footage before tracking, be sure to have that footage inside SI as your rotoscope image or the track will not match up.

Hope this helps again,

rob

[Rork]

Found this on the web, it deals with sensor sizes/filmbacks:

Sony publishes Guide to Sensor Sizes:
http://provideocoalition.com/index.php/ ... sor_sizes/

earlywill blog on finding lens/filmback settings:
http://www.earlyworm.org/2008/02/0197-0111.html
http://www.earlyworm.org/2008/08/filmbacks.html
http://www.earlyworm.org/2008/12/filmba ... t-iii.html

hope this helps someone,

rob