6 votes
Accepted

Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

It is because in the case of fundamental matrix, each correspondence point relates to only one constraint(i.e it maps a point to a line in other image). Hence 8 correspondence points are required. ...
harshkn's user avatar
  • 241
2 votes

Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

consider the number of DOFs and number of constraints. On the one hand, the matrix H contains 9 entries, but is defined only up to scale. Thus, the total number ...
doplano's user avatar
  • 143
1 vote

Should we use all $N$ correspondence points to compute Homography or just $4$ points?

It's generally better to use all the points you have, since often, errors are independent per point. given my correspondence points are good, shouldn't there be an exact solution Sure, but in ...
bogovicj's user avatar
  • 111
1 vote

3D world homography matrix calculation

Check out my answer to a somewhat similar problem here. You will need to generalize $$ x = A_x m^2 + B_x mn + C_x n^2 + D_x m + E_x n + F_x $$ to $$ x_{new} = A_x x^2 + B_x y^2 + C_x z^2 + D_x x ...
Cedron Dawg's user avatar
  • 7,520
1 vote

Homography Matrix Correlations

Consider three points $A$ in image 1,$B$ in image 2 and $C$ in image 3.$H1$ is the homography matrix from $A$ to $B$ and $H2$ is the homography matrix from $B$ to $C$. Then, $$B = H1A$$ $$C = H2B$$ ...
Navin Prashath's user avatar
1 vote
Accepted

How are the scaling parameters included (extracted from) an essential matrix?

The Essential matrix is defined only up to scale, so you cannot extract scale from it. In other words, if you multiply $t$ and all the 3D world points in your scene by a constant factor, the essential ...
Dima's user avatar
  • 5,091
1 vote

Obtain motion between image features by means of the homography matrix

First, calibrate your intrinsics: The focal lengths and the principal point. Homography is not really a rigid transformation and rather a mapping of a plane onto another one. What you really need is a ...
Tolga Birdal's user avatar
  • 5,465

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