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matching an AE 3D camera and 3D comp to the perspective of an existing photo
I searched the forums for “3D,” “camera,” “match,” and “perspective,” but I didn’t find the answer I’m looking for.
I have a 3D comp I have created in AE. Animation is all done of layers moving in 3D. I have a still photograph that I want to composite my 3D comp into, and I need to get the perspective to match as precisely as possible. What technique should I use to get these elements to line up? I tried to “eyeball” it by just pushing the 3D comp around in 3D space and rotating it and the camera, but I don’t think I was ever going to get it right. Too many variables. Seems like there should be some way to do this “properly.” I’m using AE 7.0 and Photoshop CS2.
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6 Replies
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do you have any reference in the photograph that you know the height and width of like a wall or window. If so, you can recreate this element in AE and then align the element to the picture. That is the easiest way in my opinion.
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Let’s say I don’t…
😉
However, even if I did know specific dimensions, this still wouldn’t help me match the perspective since I would still need to play with 3D camera position, orientation, focal length, etc. etc. etc. I’m basically trying to match a square to a square. So the trick is getting the camera in the right spot to look at my 3D comp square so that it perfectly matches the square in my still photo (background plate).
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> I have a 3D comp I have created in AE. Animation is all done of layers moving in 3D.
Then you have a 2d movie, yes? The source is now irrelevant.
> I have a still photograph that I want to composite my 3D comp into, and I need to get the perspective to match as precisely as possible. What technique should I use to get these elements to line up? I tried to “eyeball” it by just pushing the 3D comp around in 3D space and rotating it and the camera, but I don’t think I was ever going to get it right. Too many variables. Seems like there should be some way to do this “properly.”
Draw some lines on your photo that indicate the vanishing point on the horizon. Locate the horizon. You don’t need to be working in 3d space in AE, all you’re doing is compensating for apparent perspective. That is a simple application of distortion effects. You cannot use 3d space since you have no absolute and measurable references, as Mark has pointed out. the photo is not 3d.
What you’re doing is no more complicated than perspective corner pinning. You may be confusing the fact that your original animation was 3d but now it’s 2d.
bogiesan
This is my standard sigfile so do not take it personally: “For crying out loud, read the freakin’ manual.”
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Hi bogiesan,
I wish it was that simple. My 3D comp has layers that rotate and stuff, so it is not just a 2D movie now. I’ll try to explain more clearly what I’m doing. I’m recreating one of those tri-sided rotating billboards. The billboard is made up of a bunch of vertical “stripes” that are actually triangular prisms. Different imagery on the three sides. When the panels rotate, I want to be able to see the dimensionality of them that is retained in a 3D comp. I’ve basically built one of these in AE’s 3D space by how I’ve positioned my 3D layers. I’m compositing this synthetic, 3-dimensional billboard on top of a static background plate. I totally need to maintain the 3D nature of my 3D comp, so basic corner pinning will not cut it.
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It sounds like it should be a slam-dunk, but it isn’t yet. One trick is to pick a lens that is a likely match for the original lens (guess by eye), then make a grid of solids. These solids are in different positions, but all the same angle, as if they are all auditioning for the part of the billboard in the shot. Move your camera around until one of them matches the perspective and position of the original shot. Scale it up until it matches the size of the billboard in the shot.
This is where your fancy 3D billboard should go. Leave the camera alone now, and move the billboard to that position.
It just might work …
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> I’m recreating one of those tri-sided rotating billboards.
ah, that’s totally different. So easy to misinterpret this stuff, eh?
Interesting challenge, the others have provided some interesting ideas. I’m trying to envision doing it in real space with a real billboard.
You must use a 3d comp.
But you don’t really need the photograph to be a 3d object. You just need to see your 3d precomp through a hole you could mask off out of the 2d photo. Or, if you’ve got the alpha properly set, just drop the 3d precomp of the periaktoids on top of the 2d photo. and start trying to match the lens.Tough challenge, aye.
bogiesan
This is my standard sigfile so do not take it personally: “For crying out loud, read the freakin’ manual.”
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