Camera Calibration using Zhang's Method Slides: www.ipb.uni-bonn.de/html/teach... Cyrill Stachniss, Spring 2020
Пікірлер: 42
@eason_longleilei4 жыл бұрын
Thank you, Prof Stachniss. The entire course is clarity and the equation deduction is easy to understand. We like these series of online courses.
@letatanu3 жыл бұрын
Thank you, Prof. Stachniss. Your courses are enjoyable.
@MatyyRdk4 жыл бұрын
Thanks so much for that, it helped a lot!
@sathyanarayanankulasekaran16742 жыл бұрын
I went through Zhangs paper....without this explanation, it wud have taken months for me to understand...thanks a lot
@CyrillStachniss2 жыл бұрын
My pleasure - and I may say that it also took me a while when I first tried to dive into it…
@yanhairen72933 жыл бұрын
Thank you so much . You are are really good teacher
@rohanjoshi5233 жыл бұрын
Amazing series! This is extremely helpful for all students across the globe. If you are taking suggestions for future topics to make videos on, could you consider making a series on Visual SLAM? That would be very helpful. Thanks.
@adelsaleh57694 жыл бұрын
Your series are the best i ever watched.
@CyrillStachniss4 жыл бұрын
Thanks :-)
@sags4 жыл бұрын
couldn't agree more. Kudos 🤟
@hssensana16784 жыл бұрын
absolutly !!!!!!
@hssensana16784 жыл бұрын
thank you so much for this video and the one dealing with the DLT , it helped me a lot to understand the Zhang paper.
@mahmodsahal34143 жыл бұрын
Hi, hssen, please could we talk?
@lordstinson80953 жыл бұрын
@@mahmodsahal3414 WTF MAHMOD!?
@mayanksharma7354Ай бұрын
Thank you for this video.
@Labliequan3 жыл бұрын
I want to implement Zhang's Method and using your lecture to help with it. I noticed that on slide 40 the vij vector is not defined the same way as in Zhang's paper. The elements 3 and 4 are exchanged. So I'm asking myself: does the order of the elements matter? Is the exchange on purpose or just a mistake?
@stevea82013 жыл бұрын
Question, you go over how to obtain the intrinsic matrix (K), but is it also possible to get the extrinsic matrix using this approach?
@fransmulder93263 жыл бұрын
In an attempt to implement this, I used a single checkerboard image with known xy-coordinates of the crossings as well as the corresponding pixel coordinates. A gradient descent method based on least squares errors was computationally faster and gave me both the intrinsic as well as extrinsinc parameters for that picture. Is this coincidence? When taking computational effort and robustness into account how does zhangs compares to such a gradient descent m eethod?
@jj-ry8xv3 жыл бұрын
thanks for your video! question, what if I also want to find out the rotation matrix and transition vector? what should I do to calculate them after the K matrix is found? would DLT work for finding out R and t? thanks again!
@TheTacticalDood2 жыл бұрын
Yes, the direct linear transform method can be used to find the camera pose.
@sinaebrahimifarsangi45842 жыл бұрын
Hello Professor, The original paper on Zhang Calibration mentions that this calibration requires at least two images but you mentioned we need at least two. Is there something that I am missing ?
@wolftribe663 жыл бұрын
what kinda workouts you do?
@hermesingenui26533 жыл бұрын
Hello, thank you very much for your explanation, please i want to know if we can use camera calibration to measuer a size of an object without knowing the distance lens/object ?
@CyrillStachniss3 жыл бұрын
Not from a single image. Even if you have multiple images, you can only measure it if you know the length of the baseline vector.
@e-ausil5 ай бұрын
Hi! Thank you for the video! I have a doubt: what if we want to set zero-skew?
@trendz90412 жыл бұрын
I’m having trouble heat mapping to calibrate my checkerboard I don’t have enough sunlight. Any ideas how I solve this ?
@Hellbioy101 Жыл бұрын
How do we ensure the matrix B we obtain from the least squares solution is positive definite? The Cholesky decomposition will only work if it is positive (semi) definite
@pu239 Жыл бұрын
I got this exact problem :/ Did you figure anything out?
@yahiabammoune17162 жыл бұрын
thanks for your video! question, are you sure that K is invertible matrix? because si a projection matrix (from 3D to 2D)
@CyrillStachniss2 жыл бұрын
K itself covers only the (linear) intrinsic calibration parameters is a 3x3 matrix and yes, it is invertible.
@poojakabra14792 жыл бұрын
@@CyrillStachniss so if we multiplied pixel coordinates by inv(K) will we get 3D coordinates in camera coordinate system in the true scale?
@a1k0n4 жыл бұрын
I never realized a homography matrix was just a projection matrix with the Z column deleted.
@TyNguyen-hd2wm3 жыл бұрын
It's not 100% correct though. Homography matrix can be formed by removing either r1, r2, r3 or t in the homogeneous transformation matrix. [R|t].
@rohanjoshi5233 жыл бұрын
Any NxN non-singular matrix is a homography. Since we deal with a 2 dimensional projective space, we represent homographies as a 3x3 matrix that can transform points on one plane to another. Hence any non-singular 3x3 matrix is a homography.
@andrekestler82563 жыл бұрын
Short question for the matrix B: Why is B a symmetric Matrix?
@rohanjoshi5233 жыл бұрын
Write down the expanded form of( K^-T * K^-1). Since K is upper triangular, the product will be symmetric.
@javocremona3 жыл бұрын
@@rohanjoshi523 and why B is positive definite?
@rohanjoshi5233 жыл бұрын
@@javocremona Try performing elimination and see the signs of the pivots. All the pivots should turn out to be positive. The sign of the pivots are the sign of the eigen values.
@javocremona3 жыл бұрын
@@rohanjoshi523 Thanks!
@Theproaff3 жыл бұрын
Shouldn't the matrix H have 9 degrees of freedom? 5 intrinsics and 4 extrinsics
@TyNguyen-hd2wm3 жыл бұрын
it's up to the scale so we can normalize all by element H_{33}, making it 8 Dof.