Hatrack River Forum: Math folks, here's a question

This is topic Math folks, here's a question in forum Books, Films, Food and Culture at Hatrack River Forum.

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Posted by Earendil18 (Member # 3180) on :

I have a picture of an SR-71 taken from a certain height and POV. I need to find out how to orient my OWN video camera so that when I composite my actor walking up towards it he's in the correct perspective and meshes with the background correctly.

My camera isn't going to be as high up as what was used for the shot, but it needs to be in the correct orientation.

Is there anyway to derive the proper angles etc from a 2d picture using some kind of...higher-than-me math?

Here's the pic.
http://rapidshare.com/files/331073/EC90-105-3.jpg.html

Posted by MightyCow (Member # 9253) on :

I'm no math expert, but I can tell you that the horizon on that picture isn't square, so if you're going to fix that, you'll have to keep that in mind when you figure out the rest of your problem [Smile]

Posted by James Tiberius Kirk (Member # 2832) on :

You could obtain a simple 3D model of a Blackbird and overlay it on the photo. If you adjust the camera so the render matches up with the the picture, you could use the vector between your camera and the orgin (where your SR71 model would be) as to obtain your camera angles.

Of course, that's all theoretical ... I've never tried it before.

--j_k

Posted by Nighthawk (Member # 4176) on :

There's a lot involved. We need the dimensions of the plane itself, which I'm guessing could be gotten from any number of military sites.

That, in conjunction with the camera's FOV and, with an absurd amount of work, I'm guessing approximations can be made. Right now I can't even begin to think about where to begin, but it sounds possible.

Easiest way would be the recommended way: find an SR71 model (I'm sure they're around), or at least create a boxy version of it using the plane's dimensions inside of 3DSMax (or equivalent). Then take the picture and set it as the background to the image, then move the camera so that the wireframe of the model matches the background.

Posted by Earendil18 (Member # 3180) on :

If someone could point me to an SR-71 model that would be awesome. The only one I've found is a high res 3dsmax model that costs 179-199 to download. [Big Grin]

I guess there's the hit and miss approach. [Wink]

Posted by Nighthawk (Member # 4176) on :

Well, you don't need an exact model. If you're familiar with 3DSMax, all you need is to create points, blocks, etc... at the right dimensions.

Look at the way movie CGI is done. They don't usually park a full-size plane on set, but instead have tennis balls or the like positioned so that the actors have a spatial point of reference.