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Compositing actor to 3D virtual set

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Evan Robinson
Compositing actor to 3D virtual set
on Aug 6, 2012 at 8:36:21 pm

Hi,

I am having a hard time compositing a 3d actor in a 3d virtual set. I tracked the shot using AE's built in 3d tracker.(I am trying to motion track a actor into a 3d virtual set that has camera movement) Now, i am trying to the actor on top of the ground, but no matter what i do, it does not work. The ground always slips, and does not stay under the actor. Is this possible to do in After effects and its tracker, or do i need to do it in a 3d program like blender?

Any help would be appreciated


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 6, 2012 at 8:38:00 pm

I probably did not give you enough info to answer the question, so ask as many as you need.


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Jeff Brown
Re: Compositing actor to 3D virtual set
on Aug 6, 2012 at 9:45:50 pm

One thing you could clear up, Evan (can't tell from your wording):
You are tracking the actor footage, which has the moving camera? Or you are tracking the virtual set footage?

2 big things to prevent slipping:

Make sure the track solves for the proper field of view (lens), then duplicate that in the 3D set. I've only used SynthEyes for 3D tracking, not sure if AE gives you this info.

Also, make sure the scale of everything is correct; you actually need to use "real" units.

-Jeff


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 6, 2012 at 10:00:45 pm

I am tracking the live footage. Is it better the track the virtual set?? Also the virtual set is some thing that i made. You said

Make sure the track solves for the proper field of view (lens), then duplicate that in the 3D set

Can you please explain that better, Thanks


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Darby Edelen
Re: Compositing actor to 3D virtual set
on Aug 6, 2012 at 11:47:30 pm

[Evan Robinson] "I am tracking the live footage."

What does the live footage look like? How is the camera moving? Do you have tracker markers/parallax stands on a green screen? If your talent is moving in the shot, do you have them matted out from the tracking?

Darby Edelen


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 6, 2012 at 11:53:00 pm

The actor nor the green screen is moving, There is not much parallax, and even if there were 3d camera tracker built in can not manually add user features


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Darby Edelen
Re: Compositing actor to 3D virtual set
on Aug 6, 2012 at 11:56:43 pm

[Evan Robinson] "The actor nor the green screen is moving"

You really shouldn't need to track in that case. Ideally you would have information from the day of the shoot such as camera height, distance from subject and focal length. With those variables nailed down it shouldn't be too hard to orient a virtual camera in such a way as to match the perspective in the shot.

If there's no camera movement in the shot I'm not sure how any camera tracker would be able to produce a usable solve.

Darby Edelen


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 12:42:28 am

You must have misunderstood me, there is camera movement, but the actor is not moving.


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Darby Edelen
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 2:25:22 am

Okay then, back to the drawing board.

The built-in 3D Camera Tracker in AE doesn't have as many ways to adjust the track/solve as other tools so you may be pretty much stuck. You might try specifying a field of view for the solve or masking out some portions of the frame if the tracks are bad there, but there's not much else you can do.

Darby Edelen


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 3:29:01 am

The track is fine, in fact, the shot tracks really well. l just don't understand how to get this 2d layer of my actor in the 3d virtual set with the actors feet touching the ground of my virtual set. I can position the floor correctly, it seems to work, but when i go the the custom view 3, i see that the actors feet are not really touching the floor. So if i add a 3d light, the actors seems to be on the ground till you see the shadow, and you can tell that the actor is actually floating above the ground. What i did was make my actor's layer 3d, which moves it out of position. I then position the 3d layer of my actor to to fill the entire camera like its 2d equivalent layer. Then i parent the 3d layer of the actor to the camera, so it is always in front of camera. Is that correct?


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Roland R. Kahlenberg
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 9:23:12 am

It sounds like you're confident that you've tracked the backing plate well enough to do the job. I assume that your confidence is based on trying out the solve by actually placing solids or some other layer into the scene. If this is the case, then re-position the actor's Anchor Point to his feet. Then Shift+Parent (new feature in CS6) the actor to the solid.

Shift+Parent forces the child layer to adopt the parent layer's (the solid) transform properties. IOW, ensure that a solid can be placed into the solved scene to test for the accuracy.

If this doesn't help then post a result to show what the composite looks like. And do let us know the solve stats.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 11:54:52 am

That is not possible, since the actor layer is parented to the camera. It cant be parented to both.


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Roland R. Kahlenberg
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 12:36:37 pm

[Evan Robinson] "since the actor layer is parented to the camera. It cant be parented to both."

WHy are you Parenting the actor to the camera??????????????

This is likely the cause of your issue!!!!!!!!!!!!!!!!!!!!!

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 12:48:25 pm

Im parenting it so that the actor layer always fills the screen. Because it is a 3d layer, it moves around like everything else


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 12:52:34 pm

That layer needs to be filling the 3d camera, so i parented it to the camera. If i don't, since the camera is animated, it moves around like the other 3d layers, but it does not need to since it already has real camera movement in real life.


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Darby Edelen
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 2:57:50 pm

Well, either the track isn't as good as you think it is or the location and orientation of the solid doesn't quite match the floor.

Also the actor layer being 3D and parented to the camera may cause strange results in some cases. I recommend leaving the actor layer 2D.

Darby Edelen


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Tudor "Ted" Jelescu
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 4:04:51 pm

After reading the whole thread it seems to me that there is one major issue- why are you making the actor layer 3d?! You have a Camera moving in the "real world" shooting the actor- right? You are trying to match a virtual camera to "shoot" a virtual set with the same move and that is why you track with the 3d tracker and apply data to the virtual camera - this way the virtual move in the virtual set matches the one in the real world. So you do not need to make the actor layer 3d, parent that to the camera or anything else- it just needs to stay put as a 2d layer with a matte. If the track is good and the virtual set is correctly positioned in front of the camera, then your actor should "stick" to the floor.

Tudor "Ted" Jelescu
Senior VFX Artist


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 4:17:36 pm

That's exactly what i though, I decided that if i made it 3d,then parented it to the camera, I could easily shine a light off that layer and have the shadow cast on the ground. How do i get the shadow then? Here
http://www.hollywoodcamerawork.us/vfx_sampleclips.html on the second clip, they talk about this topic. When they do that, is the actor layer 2d, Or is it 3d, and actually touching the virtual set?


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Tudor "Ted" Jelescu
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 6:39:06 pm

There are several ways of getting a shadow:
one is to actually get it from your chroma, the actual shadow of your talent- but that involves some good keying skills and patience.

The second is to fake it using a third party plugin (Shadow from RedGiant Wrap, Boris...) or by duplicating your layer, making it 3d, changing the anchor point to the bottom, crushing all grey values to black, blurring the image, cutting a mask at the top with a feathered edge to create the illusion of the shadow losing intensity as it goes away from the subject and then positioning the layer in 3d to match the perspective of the floor and the bottom edge of the subject.

The third would be to make the actual layer of the actor 3d, position it correctly in 3d space inside the virtual set and shining a light on it to have it cast a shadow. In this situation though there should be no camera move to match - the only move should be the virtual one.

Tudor "Ted" Jelescu
Senior VFX Artist


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 7:08:44 pm

I dont think you second solution would work. I think this would require a render of the shadow 2d motion tracked to the ground


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Tudor "Ted" Jelescu
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 7:46:15 pm

If you use a Shadow plugin like Wrap/Shadow, you need to animate the shadow end to change perspective with the scene. If you use a 3d duplicate of the 2d actor layer, once it's positioned correctly it will move with the floor as the camera moves.

Tudor "Ted" Jelescu
Senior VFX Artist


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Darby Edelen
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 7:10:10 pm

The problem with only parenting to the camera is that your actor layer will always be the same distance from the camera, which will not place it in the 3D scene properly.

You might be able to more accurately place the 3D actor layer using some of the track points, but in order to eliminate doubling up on the real camera move you'd have to use some heavy duty trickery, it may not even work. I'd start by trying to auto-orient the 3D layer to the camera, then I'd add an expression to scale the 3D layer to keep it the correct size. I haven't tried this, and it's likely that it won't look entirely correct.

I'd probably use the 2D actor layer and create a 3D actor layer to cast shadows only. Of course, as described above, you'd have to figure out how to get this 3D actor layer to occupy the right space and orient/scale itself properly.

Darby Edelen


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 8:18:50 pm

How to professional companies do this? Do they use something like the red giant plugin? I don't think it is possible to get the shadow correct if the layer is 3d. I think that the shadow layer must be 2d, and 2d motion tracked to the feet, would this work?


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 7, 2012 at 8:19:25 pm

You helped me with the previous problem, but the new problem, as describe is the shadow


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Conrad Olson
Re: Compositing actor to 3D virtual set
on Aug 8, 2012 at 12:00:09 am

Shadows in 2.5D situations are never as straight forward as you would like.

I don't know if you can use the same projection techniques in After Effects that you can do in Nuke but if you can here is what I would try:

Work out where in the 3D space the actor should be standing and position a 3D layer at that point.

Key they actor so he has an alpha channel.

Then project him from the tracked camera, onto the card. This will give you the actor in the correct position in the 3D space and at the correct scale. This is that part that I could do in Nuke easily but I don't know how you would go about it in AE so someone else on here will need to chime in. I'd like to learn if this can be done in After Effects.

Once you have the actor on the card you can use a light and that card to cast a shadow onto the other geometry in the scene. You could either use this as part of your render, or render it separately and use it as a mask to grade your BG through. This is where AE wins over Nuke at the moment. You can't cast shadows in Nuke so this doesn't work.

The short coming of this technique is that that card is only 2D in a 3D space. The shadow will look great if the light is from the front or the back, but it won't work at all if the light is 90 degrees to the card because there is no volume.

I most cases we use 2D tricks to create these kind of shadows. If we need a more accurate version we would get a match moved digi double of the actor, place it in the 3D scene, and render a shadow matte from the 3D package.

---

conradolson.com


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Evan Robinson
Re: Compositing actor to 3D virtual set
on Aug 8, 2012 at 1:40:31 am

I will consider all these option, and thanks to all for helping me one step closer to the solution


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Darby Edelen
Re: Compositing actor to 3D virtual set
on Aug 8, 2012 at 9:03:58 pm

[Evan Robinson] "How to professional companies do this? Do they use something like the red giant plugin? I don't think it is possible to get the shadow correct if the layer is 3d. I think that the shadow layer must be 2d, and 2d motion tracked to the feet, would this work?"

Generally I'd expect high end productions to do a separate key to pull the shadows from the green screen.

Darby Edelen


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