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copied!<p>We finally got this to work. We've tried several different methods, but most were failing. And some were even retrieving a non identity matrix when giving the same points as input and outputs (for example, the one from KennyTM… we must have been missing something there).</p> <p>Using <a href="http://opencv.willowgarage.com/wiki/" rel="nofollow noreferrer">OpenCV</a> as following, we get a <code>CATransform3D</code> ready to be used on a CAAnimation layer:</p> <pre><code>+ (CATransform3D)transformQuadrilateral:(Quadrilateral)origin toQuadrilateral:(Quadrilateral)destination { CvPoint2D32f *cvsrc = [self openCVMatrixWithQuadrilateral:origin]; CvMat *src_mat = cvCreateMat( 4, 2, CV_32FC1 ); cvSetData(src_mat, cvsrc, sizeof(CvPoint2D32f)); CvPoint2D32f *cvdst = [self openCVMatrixWithQuadrilateral:destination]; CvMat *dst_mat = cvCreateMat( 4, 2, CV_32FC1 ); cvSetData(dst_mat, cvdst, sizeof(CvPoint2D32f)); CvMat *H = cvCreateMat(3,3,CV_32FC1); cvFindHomography(src_mat, dst_mat, H); cvReleaseMat(&src_mat); cvReleaseMat(&dst_mat); CATransform3D transform = [self transform3DWithCMatrix:H->data.fl]; cvReleaseMat(&H); return transform; } + (CvPoint2D32f *)openCVMatrixWithQuadrilateral:(Quadrilateral)origin { CvPoint2D32f *cvsrc = (CvPoint2D32f *)malloc(4*sizeof(CvPoint2D32f)); cvsrc[0].x = origin.upperLeft.x; cvsrc[0].y = origin.upperLeft.y; cvsrc[1].x = origin.upperRight.x; cvsrc[1].y = origin.upperRight.y; cvsrc[2].x = origin.lowerRight.x; cvsrc[2].y = origin.lowerRight.y; cvsrc[3].x = origin.lowerLeft.x; cvsrc[3].y = origin.lowerLeft.y; return cvsrc; } + (CATransform3D)transform3DWithCMatrix:(float *)matrix { CATransform3D transform = CATransform3DIdentity; transform.m11 = matrix[0]; transform.m21 = matrix[1]; transform.m41 = matrix[2]; transform.m12 = matrix[3]; transform.m22 = matrix[4]; transform.m42 = matrix[5]; transform.m14 = matrix[6]; transform.m24 = matrix[7]; transform.m44 = matrix[8]; return transform; } </code></pre>

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