Parenting the Separate Ends of a 3D Object to Two Different Nulls?

[Steve Bentley]

Hey Rikk,
You have to think about it the other way round.
Element lives inside of AE is just a flat layer. So its best to send the values of the 3D AE null layers into the values of the objects (or “particle replicator positions” as Element calls them – under each “Group”). The position and rotation of those particles shows up in the effect dialogue for element. This wont be a simple pick whip thing for a number of reasons:

1) the position of objects in Element don’t always relate as one might think to the outside world of your AE comp. So there’s usually an offset that’s required where you will add a constant value to the expression math you get from the null’s position (which you could pick whip, but only to get the initial raw value of where the null is) to feed into the object’s position in the Element effect dialogue.
2) for this kind of animation you can either use the cloning tool inside Element or as Michael pointed out (all refreshed with his new avatar – so that’s why he’s thinking so far ahead of the rest of us aging fx artists: he’s soo young!), you can make what amounts to an IK chain with a set number of objects in Element – each would be in its own group. (the key to Ik chains is what the objects “look at” as they move around.) Again these are calculations you have to add into the expression that drives where the “particles” are positioned.

So while this is doable in AE, I think its’ going to be easier in C4D for a bunch of reasons.
1) You can have C4D set up the IK for you and it just kinda works.
2) you can impart dynamics and self collision math with just a few buttons pushes – this is perfect for chains.
3) the data from the nulls and the camera and the lights in AE can be sent into C4D (and visa versa) so that everything lines up and you have targets to play with in your IK chain.
4) you’ll probably have better luck with any depth effects (including penetration) like haze or blur.
5) you might also have better luck with the motion blur in C4d. When you get into expressions often the thing you want to blur isn’t moving as far as ti appears to be so AE blurs it minimally.

Then the only decision is whether to have C4D render the chain and you comp the resultant frames in AE or you have AE do the C4D render for you and bring in the C4D project in as a layer in AE. Keep in mind that while you are getting the image of true 3D geometry in the C4D layer inside of AE, it’s only a layer at that point and as such is flat. So if the chain goes into the distance, and there are other objects near the chain, the c4d layer will only overlap those AE objects that: are below it in the layer stack, or if the chain’s layer (assuming a 3D layer) is above the zdepth assigned to the 2d “cards” of all the other 3d AE layers

I’m not sure if packages like DUIK (free by the way, but there are others) can do IK chains in depth or not but you could use them to animate dummies or nulls in AE and then get the data from those and pass the position and rotation data of each to element3D objects.

[Rikk Wolf]

Hey Steve,

Thank you for the in-depth outline! I hope I’ve said how much I appreciate your time.

Alrighty, you’ve sold me on Cinema 4D. I’ve spent the last several hours watching tutorials to get the basics. I really like the simplistic interface.

I’ve built a chain with individual links each as their own objects in Cinema 4D Lite but I’m uncertain of how to proceed from here. I’ve searched for about 15 mins. on how to import my two null objects (one tracked from the actor’s fist, one from the saw blade I need to attach the other end of the chain to) into C4D but everything I find online is centered around taking data from C4D into After Effects, not the other way around.

I’ll keep searching for tutorials that apply to my situation. I’m really anxious to see this IK system at work.

[Steve Bentley]

There’s now an export function in AE. (file/export/C4D (different versions have the list menu item listed differently).The objects have to be 3D solids or nulls or lights or cameras. Make sure to label them and having different colored solids helps you see them in C4D too.
That creates a project that you can open in C4D and the exported objects will dance around in time inside C4D.
One thing of note. For things like expressions you sometimes have to collapse the expression into keyframes to get the export to give out the animation info to C4D.
Make sure to use the camera from AE in C4D too so you are looking through the same lens. And the AE comp size has to match render size in C4D.

[Steve Bentley]

Once you have everything working in C4D you can either import the C4D file as a layer into AE and have AE render the whole thing for you or render out the C4D file (through the imported camera from AE) and bring those frames in as a layer into AE.

You can also bring the C4D project (via the render settings Compositing Project File under Save) into AE as you work to check progress and how things are lining up inside AE You must put an external compositing tag on any object in C4D that you want to export and these will show up as nulls in AE (assuming you just want to check animation and position and not actually render) only cameras and lights will come in as actual 3D objects. You can color each exported object in C4D with the external compositing tag so you know what object is what in AE. With this you are just checking the anchor points and how they move, no objects actually get exported.
The “project” you open in AE from this process shows up as a comp and you have to dive into the comp, pull the items out of the comp and place them in your master comp so everything lives together in the same “space” You won’t need the camera or lights.

[Rikk Wolf]

Hey Steve,

I’ve had some luck getting things into C4D from After Effects and while my nulls transfer over, unfortunately, their motion or “position” data is not showing up in C4D.

To try an’ fast track this and wrap things up, I decided to shoot a quick video showing preciously the issue. Should be faster and more accurate than describing things in text.

Here’s the link: https://youtu.be/iA1hTG1G0vw

In the meantime, I’ll read over your previous instructions to see if I missed something. Thanks again!

[Steve Bentley]

hard to see which null is the tracker null but it looks like it might be 2D only? If that’s the case thats why they aren’t showing up. You can only export 3D nulls and solids to cinema.
Could that be it?? We can make that null 3D and not loose the data which would fit it. But it still is not moving in depth, just in x and y.
Just thought I’d blast that off quick and it might help – going to watch the rest of the vid now

[Steve Bentley]

Wanna upload the AE project? (I don’t need the footage) and I’ll see if there is something obvious that’s not working right. Depending on the version of AE and C4D the export and import can work a little different. For some stuff I even have to import files into AE5.5 and then convert it to 2019. I currently have 3 different exporters for C4D inside of AE that I use depending on the case.
See if there’s a version of C4D under help ( i know its lite but I don’t want to send back a file thats too new for your version. )

[Rikk Wolf]

Yeah, my nulls were given motion track data from only X and Y movement. To be honest, I don’t know how you even track movement in Z space. By tracking “scale” from the motion tracker?

I am totally willing to share the .aep file with you but I’ll need to give you the download link privately. Hit me up at wolf.rikk@gmail.com and I’ll send you the file.

Super cool of you to offer, I can’t thank you enough. I would’ve never thought something like this would be so complicated. Cheers!