Copy & Relocate A 3D animated Composition within Footage

Question

I have created these animations of ink dropping and spreading on the top of this table I filmed. I used the 3D Camera Tracker effect to create a bunch of 3D points on the table, I created a 3D null object on one of those points, and I attached to it stock footage of ink drops falling (that were also made into 3D Layers). For the spread effect, I used the same process with footage of ink spreading but had to include some additional scale, position, and z-axis-rotation change keyframes to get the proper effect. This has worked very well. Now I have two complimentary comps that I need to duplicate and move to other 3-dimensional locations on top of the table.

Moving the Ink Drop comps is easy enough; I simply select all the layers within that comp, copy them, paste them into a new comp titled "Ink Drop 2", select all the layers in the Ink Drop 2 comp, and drag them to the desired location on top of the table. This changes the Position properties of all the layers together, and that's it. Done and done. However, the spread comp is more difficult.

Since the Ink Spread comp already includes position change keyframes as part of what makes the composite itself work visually, I can't use that same transform parameter to change the overall location of all the layers like I did before. I need some other way of moving the layers inside the composite.

I tried turning the whole Ink Spread comp itself into a 3D layer attached to the null object (so it had some idea of where the X, Y, and Z axes were located), but that messed up the scaling of the layers within. I tried detaching that comp from the null object, but that messed up all the rotational axes. I was thinking of using an adjustment layer inside the Ink Spread comp itself, but those seem to only apply effects to comps underneath them and not layers, which would be no better than the previous solution.

I'm sure there's a very simple fix to this. But, this is my first big project in AE, and I'm a little lost.

Thanks!

Rick Gerard · Accepted Answer

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As long as the perspective of your animated ink drop comps works in 2D, when you attach the nested comps in the Camera Tracked shot and the reference origin and ground plane and reference solids are perfectly attached to the surface Shift + parent will line up the ink spread comps perfectly. All you should have to do is rotate them on their vertical axis to fine tune the adjustments. After animating the ink spread comps and have camera tracked the shot it should only take a few minutes to place the ink spread comps in the scene.

If you have ink drops falling to the surface as footage you can also line them up with the reference solids using the Shift + parent trick, then rotate them upright and set them to orient to the camera. If the video of the ink drops are properly prepared that should also go very quickly.

So just to review for others following this thread, if my project involved a camera moving across a desk and ink was supposed to fall from above and spill on the desk I would:

Film ink drops falling vertically with the camera sufficiently far away to let the ink reach the desktop but close enough to be large enough in the frame to be seen in the final composite against a background that could be easily removed or, depending on the shot of the desk, film them with a stationary camera from approximately the same angle and distance from the desk where the actual camera used to film the desk would be
Film the desk making sure there was enough detail or fixed geometry in the shot to get an accurate camera track
Animate or film ink spreading against a background I could easily remove from directly above
Prepare the ink falling and the ink spreading shots in separate comps sized to fit the content
Trim the shot of the desk and perform camera tracking probably with advanced analysis enabled
Set an origin and ground plane, add a solid and a camera, edit the solid size so that it was big enough to cover the critical areas of the desktop, then add grid and check the camera track for accuracy
Add as many reference solids as I could using the camera tracker making sure their position was exactly where I wanted it to be
Add additional reference solids using the origin and ground plane solid with the grid as a guide
Add the nested ink drop and ink spread comps to the project and adjust the anchor point to the center of the ink spread motion or the point where the ink drop stream is supposed to contact the desk
Set all nested comps to 3D and then shift + parent them to the reference solids
Adjust the orientation and scale of the nested ink comps
Turn off or delete the reference solids, make final color and edge adjustments and render

That would get you to a shot where ink falls on a desk and spreads out with the least amount of work.

Rick Gerard · Answer

I'm not really following your workflow. Maybe there is a little misunderstanding of how the Camera Tracker works.

The only keyframes that are added when you use the Track Camera feature are for the camera. If you do not set an origin and ground plane before you start adding the camera and the nulls or placeholder solids the camera could be pointed anywhere in AE's 3D world so the coordinates do not match up with another composition. When you set an origin and ground plane, at that point in time, If you add a reference solid and a camera the solid will be at 0,0,0 and if the plane you select is horizontal, the orientation will be 270º, 0º, 0º. The camera could be anywhere and the camera's orientation could be anywhere. This means that none of the data from the camera tracker is usable in another composition with another shot.

If you do not set an origin and ground plane and put a reference solid there it's awfully difficult to line things up in the rest of the shot if you are not lucky enough to have at least 3 trackers fall where you want to place things.

Now on to your problem. Let's just talk about one ink drop. Some part of the ink drop should stick to the surface and some other part should run downhill or spread out. I take it that you want to animate one ink drop and then duplicate it so that it falls on other parts of the table. The easiest way to do that is to position a reference solid using the camera tracker's points or set a grid on the solid placed on the origin and ground plane and use that for reference. When you get the second solid, easier to use than nulls because you can actually see if they are sticking to the surface, then you could simply duplicate your first animated ink drop, then hold down the shift key and parent it to the reference solid and it would move to that location. If the reference solid sticks to the surface properly, the animated ink drop will do the same. You can then turn off the reference solid, my preferred method because sometimes I need to go back and make adjustments or delete it if you are sure you are done with it.

That's how I would approach the problem you are describing. Without a reference solid at the origin and ground plane and other reference solids in the scene, it's almost impossible to move things into the right place. My reference solid at the origin and ground plane almost always has a grid applied and it's big enough to cover most of the surface. I keep it there until the composite has been checked for accuracy and all of the motion is perfect. For example, here's a shot set up to add objects to the arena. The grid is on the reference solid at 0,0,0. This gives me a really good way to check the accuracy of the camera solution and an easy reference for placing other objects in AE's 3D world:

After everything is inserted I'll just turn off the layer. By the way. It took seven tries to get the origin and ground plane in the right spot so the grid stuck perfectly to the arena floor. Only one camera solve with detailed analysis turned on, but seven tries to find the right combination of trackers to define the surface.

Without seeing your comp it's pretty hard to give you any better advice.

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