Conversion of 3x1 or 1x3 cv::Mat to cv::Point3d?

Question

I\'m dealing with some code in which a do a lot of 3x3 matrix multiplications an also some translation of 3d points using rotation matrices, etc. I decided to use OpenCV core fu

Answer 1

cv::Point3d has a constructor which allows direct creation from cv::Mat:

cv::Mat mat(3,1,CV_64FC1);
cv::Point3d p(mat);

Another possibility you may not have considered is using cv::Matx instead of cv::Mat for your mathematical operations. I find it is easier to use, and offers more functionality, like multiplication of Point types without needing a conversion:

cv::Point3d p(1,2,3);
cv::Matx33d m = cv::Matx33d::eye();
cv::Point3d p2 = m * p;

cv::Matx is also statically allocated, rather than dynamically (like cv::Mat), in case you really need that extra little bit of performance. However, as in all performance-related advice: make sure what you're optimizing is actually a bottleneck by profiling.