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External Compositing tag from C4D

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Marc Lucas
External Compositing tag from C4D
on Feb 15, 2012 at 11:13:10 am

Setting up an External Compositing tag (and selecting solid as the option) from C4D on a single plane which is the front of an iPad screen. I've set the dimensions so that the solid is the same as the plane so a simple replace in AE. When I bring it into AE the solid isn't flush with the rest of the 3D odject is about 90degrees off. Why doesn't it come in the right place, what have I got to look out for?


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Marc Lucas
Re: External Compositing tag from C4D
on Feb 15, 2012 at 11:43:42 am

After digging in AE I've found that one of the main problems has been that the solid orientation setting on the X axis was set to 0 but a small adjust to 90degrees sorted the problem. However I still had to change the size of the solid to fit where it should of on the solid. Any thoughts on why this is?


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Marc Lucas
Re: External Compositing tag from C4D
on Feb 15, 2012 at 12:37:43 pm

Also whilst successfully getting my solid to sit on the right place on the 3D object in AE I now see the solid on the front (which I wanted) but when the object spins round I see the solid on the back as well but I don't want that because it obscures the back.


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Walter Soyka
Re: External Compositing tag from C4D
on Feb 15, 2012 at 12:54:13 pm

[Marc Lucas] "Also whilst successfully getting my solid to sit on the right place on the 3D object in AE I now see the solid on the front (which I wanted) but when the object spins round I see the solid on the back as well but I don't want that because it obscures the back."

You need to assign an object buffer to your plane in C4D (via the compositing tag), then add an object buffer pass (under Multi-pass in render settings). Once you've rendered out the object buffer pass, you can use it a matte in AE to occlude your screen layer.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Marc Lucas
Re: External Compositing tag from C4D
on Feb 15, 2012 at 1:00:44 pm

I have used an External Compositing tag as per this tut http://greyscalegorilla.com/blog/2011/12/cinema-4d-to-after-effects-tutoria...

The is rotation movement of the object which goes full 360


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Walter Soyka
Re: External Compositing tag from C4D
on Feb 15, 2012 at 1:13:33 pm

[Marc Lucas] "I have used an External Compositing tag as per this tut... The is rotation movement of the object which goes full 360"

Right. The External Compositing tag tells C4D to make the coordinates of the object available to AE when C4D sets up your project.

One of the things the Compositing tag allows you to do is create object buffers, which are mattes meant to reveal and occlude the selected object when you composite it in 2D.

It's important to understand what's going from C4D to AE and what is not. C4D is passing AE a series of flattened, two-dimensional renders of your 3D scene, as well as 3D information about the camera, lights, and External Compositing object anchror points. It is not passing 3D geometry. (This is also why you shouldn't change the camera or lighting in AE from a C4D project; it won't affect the material you've already rendered from C4D, and you'll get all kinds of weird perspective mismatching.)

Since it's not passing geometry, your screen layer is a 2.5D AE object (a flat plane in 3D space) that's being composited over the flat 2D renders of your 3D scene. They do not interact -- because there's no geometry, there's nothing to occlude your screen from the camera when it's flipped around. Rendering the object buffer and using it as a matte will tell AE when to to hide that layer and when to show it, just as if it were really being occluded by other geometry in 3D.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Marc Lucas
Re: External Compositing tag from C4D
on Feb 15, 2012 at 2:04:17 pm

I do understand that but why did Nick use the External Compositing tag in his tut and it worked and synced instantly? I have used the same method and the solid doesn't come in anywhere near where it should. Also I have noticed that the solid that has been created in AE kind of flips 180 degrees on the X axis halfway through the 360 spin. Kind of getting a bit confusing:-)


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Marc Lucas
Re: External Compositing tag from C4D
on Feb 15, 2012 at 3:23:38 pm

OK this is where I'm at. I had a go using the plain Compositing tag and I successfully did that because I've done that before I could use the object buffer as a luma matte to project a video clip onto my screen. The problem is however I haven't got any position data from C4D so that the imported clip could rotate and move with the rotation object.


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Darby Edelen
Re: External Compositing tag from C4D
on Feb 18, 2012 at 2:28:56 am

You need to use the Compositing tag to create an Object Buffer and render that pass AND you also need the External Compositing tag in order to pass 3D location data from C4D to AE.

In addition, the only data that C4D passes to AE is the Axis of the object to which you applied the External Compositing tag. This means that the center of your solid will be located at that object's axis. If your object has any depth to it (e.g. it is a cube) and the axis is not located on one of its surfaces, then your AE solid's anchor point will be located inside the object.

Furthermore, your AE solid will be oriented relative to the orientation of the C4D object's axis. The X and Y axes of the AE solid will match those of the C4D axis, but since the axis systems are different the Z axis is flipped (the 180° rotation you mentioned).

To fix your issues you can either move the axis of the screen in C4D or place a Null as a child of the screen and use that to define the location/orientation of your solid's center (If you use a Null object then you need to apply the External Compositing tag to it).

Also, I don't like to use the "Solid" option in the External Compositing tag. It's unlikely that you'll get a solid of the correct size anyway. If you leave that disabled you'll get a Null object in AE instead, to which you can parent your screen footage and then transform it relative to the Null's location.

Darby Edelen


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Marc Lucas
Re: External Compositing tag from C4D
on Feb 21, 2012 at 3:51:15 pm

Thanks for the clear and concise reply. The axis issue was really confusing me so thanks for explaining that. I will now be able to move forward with less head scratching.
Really appreciate this!


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Ken Mendes
Re: External Compositing tag from C4D
on May 24, 2016 at 7:01:20 am

SOLUTION:
Bake camera and all animated elements.
Watch this,


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Dean Mellis
Re: External Compositing tag from C4D
on May 15, 2017 at 6:36:17 pm

This is a great tutorial. I will review it again once I'm home. I'm convinced my copy of R17 has a bug. I can't get a null or solid from Cineware no matter how simple a setup I make.


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