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# Reconstruction of 3D curves from two 2D projections ...

Posted on 1998-12-16
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Hi..

If I got two projections of a 3D curve on two image planes how to reconstruct the curve.Assuming we know the position and orientaion of those two iamge planes....

vijay
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Question by:vijaybrd_99

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Expert Comment

ID: 1013722
that's indeed very general.. with what program? or language do you want to do that?
it's likely that the picture format will affect the "how to do it"... give more precision please.
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Expert Comment

ID: 1013723
if you want this answered youi will have to provide all information.

to create the "Z" co-ordinate for 3d with only 2 2d sources available would not be to hard but it will have to intersect at some point and you will have to work out a grid for this.

Perspective will be another problem.
Try to convert you calculations so that you correct one view to being 90 degrees from reference to the other image.
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Author Comment

ID: 1013724
OeilNoir....!  & netmage ...!

Thanq for ur response..

The problem is that  we will be given 2d points on two image planes which are taken from two different views( may not be 90 degrees)i.e. two diffrent positions and orientaions.We will be given the position and orientation of two image planes and two sets of 2d points( no of points in each set may not the same... meansthere may not be synchronization of cameras on two image planes) of the curve on two image planes.So,how to construct the 3D curve from these 2D points. Focal lengths of two cameras also assumed to be known.

I want to solve this problem in "C"language on "Unix" operating system.Ofcourse,Language is not the main criterion.U please give good algorithm or mathematical background..
And also suggest me web sites and books that I have to reffer.

I think U got my point....

Thanq once again.
vijay
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Accepted Solution

rbr earned 400 total points
ID: 1013725
Assume that the first camera has the right coordinates for x and z
and the second camera is rotated with angular a if a is 90 degrees all will be ok. Then the second camera has the coordinates for y and z. If not you must project
(x1,z1) position of point for camera 1
(y1;z1) position of point for camera 2
(x,y,z)=(x1,y1*cos(90-a),z1)
This should be true id the camera 2 is just rotated around the z-axis and no further rotation around ony other axes. Otherwise it will be a bit more compilcated.
An other problem will be the perspective errors of the camera, but I think they could be neclegted.
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LVL 8

Expert Comment

ID: 1013726
Just thought of a program that was being used at job i was at.

There must be CAD programs out there for unix.

For what you want, it would just be a matter of creating an intersecting grid and just enter the numbers to scale.
After that it is easy to correct the 3d perspective.

If you really want to do the maths, it sounds like you'll have a hell of a matrix to construct.

Netmage
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