12.1. Projections

Once we have calibrated the camera (see Chapter 11), it is possible to unambiguously project points in the physical world to points in the image. This means that, given a location in the three-dimensional physical coordinate frame attached to the camera, we can compute where on the imager, in pixel coordinates, an external 3D point should appear. This transformation is accomplished by the OpenCV routine cvProjectPoints2().

void cvProjectPoints2(
    const CvMat* object_points,
    const CvMat* rotation_vector,
    const CvMat* translation_vector,
    const CvMat* intrinsic_matrix,
    const CvMat* distortion_coeffs,
    CvMat*       image_points,
    CvMat*       dpdrot          = NULL,
    CvMat*       dpdt            = NULL,
    CvMat*       dpdf            = NULL,
    CvMat*       dpdc            = NULL,
    CvMat*       dpddist         = NULL,
    double       aspectRatio     = 0
);