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3D camera tracker for drone rotating shot

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Sean Jahnig
3D camera tracker for drone rotating shot
on Jan 21, 2019 at 7:15:12 pm

Hi,

This question may have been asked before and I apologize if so.

I have a drone shot of a plot of land and the camera rotates around a centre point if a fairly slow manner. The goal is to overlay circles with text in them on top of the footage so that they move as part of the scene as the camera rotates.

I have tried to use the AE camera tracker which achieves ok results. I have then placed the shapes in the scene and it is more or less working the way I want. Specially I need the circles to auto orient to the camera so that despite tracking with the scene, they do not distort or rotate as they move away from the centre.

The part I am not happy with is that the circles despite being set to 'auto orient to camera' are still being distorted as they move away from the centre of the frame. I guess this is the nature of a 3D object with a camera but what I'm really looking for is a way to have the circle tracked within the scene so it appears within 3D space, but no matter where it is in the screen it should appear as a scemetrical 2D shape which is perfectly round and undistorted.

Is it as easy as keeping the circle as a 2D shape and pairing it to a 3D null that is correctly positioned in the scene? Don't even know if that is possible.

Would really appreciate any advice. Thanks


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Blaise Douros
Re: 3D camera tracker for drone rotating shot
on Jan 21, 2019 at 7:47:50 pm

If you didn't specify the Angle Of View in the 3D camera tracker, you may be working with a track where AE thinks that it's a ridiculously wide lens, and is distorting the virtual objects in the scene as a result. Look up the horizontal Angle Of View of whatever drone camera was used to shoot this, re-solve the 3D camera track, and you may get results that are more natural and fit the rest of the scene.


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Sean Jahnig
Re: 3D camera tracker for drone rotating shot
on Jan 22, 2019 at 4:59:48 am

Thanks for the reply.

I tried that but it didn't make much difference so i guess the solver was fairly close.

The problem seems to be Z space. A point in the scene that has a Z position of 2,000 has got a lot more deforming as it moves away from the center than the same object that is closer with a position of 0.

Ideally i need to link a 2D shape to a 3D point so that it exists in the correct depth but it's scale and orientation should remain the same as a 2D object does...


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Kalleheikki Kannisto
Re: 3D camera tracker for drone rotating shot
on Jan 22, 2019 at 5:38:59 pm

You should be able find the 3D position to 2D screen position expression easily by searching in the expression forum.

Not sure I understand the second part.... Do you not want the object to scale smaller in the distance? Or are you talking about retaining the appearance so that it doesn't stretch unnaturally along one axis as the objects gets close to the image edges?

Kalleheikki Kannisto
Senior Graphic Designer


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Sean Jahnig
Re: 3D camera tracker for drone rotating shot
on Jan 23, 2019 at 4:57:02 am

Thanks for the reply. I'll look into this solution.

To clarify on the second part - what i ultimately want is the circular graphics to be part of the 3D scene and move around with it BUT remain perfectly 2D and round at all times no matter where it is in the scene. Currently, tracking and placing it in 3D gives me exactly the movement i need but as the circles move around the scene they stretch/distort slightly (ie. no longer perfectly 2D and round) due to the camera distortion on the edges.

You can see a sample of what i'm talking about here - https://www.dropbox.com/s/tcq01fzoljm5voq/creative_cow_01.jpg?dl=0

I think the solution would be to do a regular track and parent to a null - but i am yet to test this.


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Kalleheikki Kannisto
Re: 3D camera tracker for drone rotating shot
on Jan 23, 2019 at 8:14:59 am

Those labels would definitely be 2D layers, not 3D layers. You can use one 3D null to 2D position with two 3D nulls, one for each end of the label line, and attach the round label to one end, and use the beam effect for the line. That way you can have some freedom to move the round labels around so they don't end up overlapping.

2D tracking and 2D nulls can also work for this.

Kalleheikki Kannisto
Senior Graphic Designer


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Sean Jahnig
Re: 3D camera tracker for drone rotating shot
on Jan 24, 2019 at 8:36:19 am

Thanks for the reply.

I'm finding it tricky to get 'track motion' working for a 2D track. I can't find a good point to track from, it always results in a tiny bit of jitter. And even when the 2D object is parented to the track it doesn't look as realistic as it does in 3D. I think the drone shot is quite complex, it's rotating and getting moving closer throughout the scene which doesn't help.

Also, 1 of the points that i need to track disappears behind an object half way through the scene so the track fails. Using the camera tracker fixes this problem because once the camera is solved, a null in 3D space is maintaining its position even when the object goes out of view.

Here's a sample of everything in 3D. My only complaint with this is the circles deforming as they move to the edge of the scene.
https://www.dropbox.com/s/9xsoe4m4j668klt/creative_cow_02.gif?dl=0

Now, if i could keep the camera tracker as it is and link a correctly positioned 3D null to a 2D object then i think i would get the behavior i need. I'm gonna get busy with that now. Please let me know if you know exactly how i can parents a 2D object to a 3D null.


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Blaise Douros
Re: 3D camera tracker for drone rotating shot
on Jan 22, 2019 at 11:45:36 pm

It sounds like you didn't need to bother with 3D Camera Tracking, then--the point tracker would do what you describe, and more easily, too.


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Sean Jahnig
Re: 3D camera tracker for drone rotating shot
on Jan 23, 2019 at 4:34:22 am

Thanks for the reply. Now that i think about it - you are right! I will give it a try.


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Sean Jahnig
Re: 3D camera tracker for drone rotating shot
on Jan 24, 2019 at 12:49:27 pm

Ok, i have got it working the way i want - thanks to everyone for the suggestions.

I did a regular track camera and then i created a 3D null in the location i wanted. After that i used the 3D null to 2D null method and then i parented my 2D graphic to the 2D null and it is working perfectly.

The way to link from the 3D null to the 2D null is by applying the below code to the position property of the 2D null where xxx is the name of the 3D null in the comp.

thisComp.layer("xxx").toComp([0, 0, 0]);


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