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Can I do a projector effect in after effects?

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ryan elder
Can I do a projector effect in after effects?
on Sep 9, 2018 at 2:50:27 am

Basically I shot a short film where a guy is in front a project and gives a presentation, while a video is being projected on to his face.

However, because of emergency rescheduling, I was not able to shoot the video that is being projected before being able to shoot the projector scene.

Is it possible to do something in after effects to make it look like the video is being projected onto the screen, and onto the actor in the process?


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Andrew Somers
Re: Can I do a projector effect in after effects?
on Sep 9, 2018 at 5:28:28 pm
Last Edited By Andrew Somers on Sep 9, 2018 at 6:41:30 pm

YIKES

The biggest problem is the geometry of the guys face, so that the video is naturally distorted on his body and face.

What you need is a way to make a mesh (i.e. 3D model) of the actor including his movement that can be projected on.

PF Track, a tracking system, has a way to make meshes like that a as I recall, though I've never done it for a projected image. I discuss some related techniques in THIS ARTICLE though I don't know if it can help you.


A possible solution for you:

Using the RAY TRACED render engine:

If you are never that close to the actor, if might work "well enough" to create a tracked mask of the actor using Mocha, then apply that to a WHITE SOLID and precompose. Then set the precomposed composition to 3D layer and portion it so it is exactly over the actor. Set the materials options TRANSPARENCY too as much as 100% (note do this in Materials and NOT in the regular transform, which should probably remain at Opacity 100%). Then project onto that and your BG. Call this layers "Projection Catcher".

Create a duplicate of this layer slightly behind in Z space and set its materials transparency to 0%, and set it to CAST SHADOWS ONLY so that it shadows the BG projection. Call this layer "Shadow Caster".

If the camera moves then you will need to create a 3D camera track so that the projection catcher and shadow caster remain in the correct relative position. I might mention you *could* try and cheat the body and face geometry by using multiple projection catchers slightly moved in Z space to emulate the geometry. This might be more trouble than it's worth, and depends on the shot and how much Z depth there is in the subject.


The projection by the way is created by using a point or spotlight, and shining it through the image you want projected. The image here again is set to 3D space and materials set to Transparency 100%, cast shadows OFF (as I recall).


At any rate, it may sound a little complicated but not too difficult to do.


EDIT TO ADD: A few weeks ago we were discussing projection in AE, in THIS THREAD and I'll mentioned that based on some experiments you want to keep the image to be projected no less than 50% scale, and not too close to the light source (see thread for more).



Andrew Somers
VFX & Title Supervisor
http://www.GeneralTitles.com


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Eric Santiago
Re: Can I do a projector effect in after effects?
on Sep 10, 2018 at 4:33:49 am

I would honestly reshoot it.
As much fun as doing it with mesh and compositing, I would just bring the actor back for a reshoot.


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ryan elder
Re: Can I do a projector effect in after effects?
on Sep 10, 2018 at 4:48:27 am

Actually I might be able to edit it as is, and it will still make sense. Sure the guy is in a room where I meant to have a projector, but perhaps he can explain things in a way, in which he doesn't need a projector to tell the plot, so to speak. I will try cutting it that way first maybe.

If not then reshoot :)


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Steve Bentley
Re: Can I do a projector effect in after effects?
on Sep 10, 2018 at 6:03:56 pm

You could also just cheat it.
Try using a combination of bezier warp and displacement mapping and some precomposing.
Set up a bezier warp (depending on the shot a mesh warp can work too or the reshape effect - what you are trying to do is simulate the big curves the face that would distort any imagery projected on it). The bezier warp would be applied to the footage you want projected, but the beziers would be shaped to match the face. You can animate this warper but you might also need to track it. The easiest way is to track the mans face, then precompose the warped projected footage and have that precomp linked to the track of the face. The trick is to move the nested footage in the opposite direction of the track (use expressions to do this). That way the footage wont move with the mans head - the head moves within the projected beam - but the warp will. You may need to open two comp windows so you can animate the warp in the precomp while the track keeps it moving to match the face in the outer comp (it's easier than jumping back and forth between comps).
You can also use some displacement to help sell the illusion too. Use the brightness of the face (you may have to crush the levels a bit to get enough contrast) to shift the precomped warp around a bit so that subtle distortions are shifted on every frame.
Projected imagery on an uneven surface can be so wacky that you can get something that looks right even though it might not be optically/mathematically correct.
You may need to roto the head so that the projected footage is masked and doesn't extend beyond the face. You can also use this roto as a blurred element to help smear the projected footage at the edges (use another displacement map or a radial blur set to zoom and the center of the zoom linked to the track point of the head). If you had shot this, the projected footage would have hit the edge of the face and the imagery would have distorted into a smear - 100 pixels might have been on the front-facing cheek, but it might only take 5 pixels to span the side-facing cheek to ear distance.



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Andrew Somers
Re: Can I do a projector effect in after effects?
on Sep 10, 2018 at 8:01:55 pm

That's a good idea Steve, I didn't even think about the mesh warp to cheat the image into position on the face.

Andrew Somers
VFX & Title Supervisor
https://www.GeneralTitles.com


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