# warpPerspective With two cams

Hello to all, I'm here to ask for advice. I have two cams that resume the same thing. A cam has a filter that only passes light ir. The other cam is a normal cam that does not pass the light ir. I use this last cam (normal cam) to detect four balls (The four balls are projected onto a wall). These four balls are the vertices of a rectangle. When I find these four points I calculate the matrix H and apply findHomography() to fix the perspective. I would like to calculate this matrix H also for the IR cam but it cant see these 4 balls. How can I calculate matrix H for this new cam? I know the distance to which the two cams are placed Can anybody give me some advice?

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You will need to estimate first the geometric transformation between the IR and normal cameras. Then, you should be able to use the estimated transformation matrix (rotation + translation) to compute the homography matrix for the other camera. See here or here for some experimentations.

( 2017-06-23 11:11:09 -0500 )edit

My problem is just one step ""estimate first the geometric transformation between the IR and normal cameras" The two cams see the screen of a video projector. A cam see what is projected on the screen from the video projector. The second cam ( that works with ir) not see the projected image. They look the same way but they do not see the same thing. I could use the video projector as a reference but I do not get the accuracy

( 2017-06-23 12:47:35 -0500 )edit

What I would do:

• calibrate the IR and normal cameras using a chessboard pattern, maybe using an infrared light to be able to see the pattern for the IR cam
• after this, the intrinsic parameters for both cameras should be known as well as the extrinsic parameters
( 2017-06-23 16:20:48 -0500 )edit