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    <p>If I understand you well, you have 4 points in the image and you know their world coordinates (you have 4 2D-3D correspondences) to find the rotation matrix and translation vector (known as the <a href="http://en.wikipedia.org/wiki/Pose_%28computer_vision%29" rel="nofollow" title="camera pose">camera pose</a>), you can use the <a href="http://docs.opencv.org/java/org/opencv/calib3d/Calib3d.html#solvePnP%28org.opencv.core.MatOfPoint3f,%20org.opencv.core.MatOfPoint2f,%20org.opencv.core.Mat,%20org.opencv.core.MatOfDouble,%20org.opencv.core.Mat,%20org.opencv.core.Mat%29" rel="nofollow" title="solvePnP">solvePnP</a> function.</p> <p>This function takes as inputs the 3D coordinates, 2D coordinates, the camera matrix (focal distance and center of projection) and the distortion coefficients, which you should have obtained by an intrinsic calibration process. The output is the rotation and translation vectors. The obtained rotation vector can be transformed in to a rotation matrix with the function <a href="http://docs.opencv.org/java/org/opencv/calib3d/Calib3d.html#Rodrigues%28org.opencv.core.Mat,%20org.opencv.core.Mat%29" rel="nofollow" title="Rodrigues">Rodrigues</a>.</p> <p>There is also <a href="http://docs.opencv.org/java/org/opencv/calib3d/Calib3d.html#solvePnPRansac%28org.opencv.core.MatOfPoint3f,%20org.opencv.core.MatOfPoint2f,%20org.opencv.core.Mat,%20org.opencv.core.MatOfDouble,%20org.opencv.core.Mat,%20org.opencv.core.Mat%29" rel="nofollow">a version of solvePnP</a> that uses a RANSAC algorithm to discard outliers.</p> <p>You can find <a href="http://projekter.aau.dk/projekter/files/14427578/A_Comparison_of_2D-3D_Pose_Estimation_Methods.pdf" rel="nofollow" title="here">here</a> a document with some theory on pose estimation.</p> <p><strong>Edit</strong></p> <p>Obtaining camera intrinsic parameters is known as <em>camera calibration</em>, you can find instructions on how to do so in this <a href="http://docs.opencv.org/doc/tutorials/calib3d/camera_calibration/camera_calibration.html" rel="nofollow">OpenCV document</a>. There is also an older tutorial with source code <a href="http://dasl.mem.drexel.edu/~noahKuntz/openCVTut10.html" rel="nofollow">here</a>.</p>
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    1. POcalling OpenCV calibration functions to calculate rotation vector and translation vector
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    1. USMilo
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    1. COhi Mr Milo ,thanks alot for your answer,but i have 2D coordinate of image only :( ,i dont have the camera parametrs too,i am beginner in opencv .i think you can help me alot.can you help me ?how i must get these matrices by 2D coordinates of image?
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    2. COthanks alot Mr Milo,I could calculate camera matrix and distortion coefficients by using circle pattern.I use barcode instead of marker.I get 2d coordinate of four corners of marker by using zxing .now how I get 3d coordinates of these corners? how use opengl to augment the obj on the barcode? does opengl need rotation and translation matrices?
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