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# Camera Tracking challenges

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 Camera Tracking challenges on Apr 9, 2019 at 10:21:43 am

Hi Forumers, it's been many years since I was last in here!

I’ve been doing MatchMoves for many years, on simple projects, generally placing small objects into scenes starting off with this fun little experiment, nearly 10 years ago(!) https://vimeo.com/14154019

However - I’ve reached a real stumbling block with my present workflow.

The plot of land inside the brick wall will be landscaped and built on. I’m trying to place a new landscape into the scene. No matter what I do, I am not getting large solids to sit well on the land. All nulls, small solids sit fine and are locked into their relative positions but when I place a large solid over the whole plot, it drifts... or it appears to drift.

Is this because the plot in the source footage isn’t an actual flat plane and is on a gentle slope?

It seems that I need to track (and generate 3D points) for each corner of the plot and then get that data into each corner of my object. Is that right, or am I way off!? I’m convinced that the problem lies with the fact the plot is on a slope and therefore my solid just isn’t accurately placed on the Y axis on all of its edges.

Is there a way (an expression perhaps?) to get four separate anchor points on each CORNER of a solid and then connect each of those anchor points to individual nulls?

I look forward to hearing views from the pros and thank you, massively, in advance for any support that you can offer.

 Re: Camera Tracking challengeson Apr 9, 2019 at 8:20:51 pm

The videos seems to be unavailable so I can't comment based on that.

[Christopher East] "Is there a way (an expression perhaps?) to get four separate anchor points on each CORNER of a solid and then connect each of those anchor points to individual nulls?"

That is essentially what the corner pin effect does. But if you need to get a null to link a 3d object to it (instead of 2d transformations only) I guess you could just average those 4 points to get something that's placed in the middle.

Try to fix that link and I'll come up with some expression that does that.

Cassius Marques
http://www.zapfilmes.com

 Re: Camera Tracking challengeson Apr 9, 2019 at 8:31:06 pm

Hi Cassius, thanks for the fast reply. I don't think corner pin works in 3D, though, does it?

I've tried the average option also but without knowing the actual angle of the slope I can't seem to get anything locked on.

The YouTube clip was set to "Private" - doh!

Fixed now.

Looking forward to hearing your views.

 Re: Camera Tracking challengeson Apr 9, 2019 at 8:44:10 pmLast Edited By Cassius Marques on Apr 9, 2019 at 8:53:26 pm

Well, first things first. Are you creating a 3d camera from the footage, right? Not just tracking motion?

If you are, after the camera is solved, the points should have 3 coordinates. You can average those to get a middle point for your mesh (if you are unable to get that point specifically in the first place). IT should just sit there. The parts that drift some should be adjusted in the model (to compensate the height differences) or we have to accept the fact that the terrain would be leveled during construction and the drift in the simulation is a result to just that.

You should, if possible, post your tests too. It's hard to see the problems just mentally.

Edit: After a second read I realized you are adding terrain to the outer parts right? So lets make sure that you got a proper track first. Then we can try to adjust it. But It helps if I could see a test.

 Re: Camera Tracking challengeson Apr 10, 2019 at 7:31:13 am

Yes I'm tracking the camera, getting good results as I usually do (small solids / nulls are sticking to their tracked positions).

If I place a solid over the entire plot and line the solid up so that the corners aline with the corners of the plot, when
the shot orbits the plot the solid appears to drift. But perhaps it's just an illusion caused by the fact that it's not actually on the correct Y plane. Right?

 Re: Camera Tracking challengeson Apr 10, 2019 at 4:54:54 pm

Yes, if you end up using too much of the trees canopies to create that Y position, the actual ground will drift a bit from the plane. But if you create a ground plane origin (in the tracker, before creating a camera), and normalize the camera's position in AE's space (meaning rotating everything until the XYZ axis kind of align). It should be easier to slowly change that Y value until you minimize the drifts. If things aren't normalized sometimes altering Y directly can mean moving it in X or Z or both. (you can still use the Y handle on the viewport, that will work).

But still, if you place landscape upon ground AND trees, you wont avoid a small drift I guess.

Good luck!

Cassius Marques
http://www.zapfilmes.com