CODEWITHSUNDEEP
computer-vision
Lunny
Lunny

Reputation: 852

ransac with homography vs 8/5 point algorithms

Im beginning to learn computer vision and I'm confused on the difference between the two.

I know that the 8 point algorithm is used to compute the fundamental matrix and the 5 point algorithm is used to compute the essential matrix. Both of which can be used to determine the relative camera pose.

I also found that the relative camera pose can be determined using ransac with homography https://inspirit.github.io/jsfeat/#multiview in the ransac method

Is there a difference between using ransac with homography as opposed to using the algorithms?

Upvotes: 0

Views: 1808

Answers (1)

Ash
Ash

Reputation: 4718

First of all, note that you still need RANSAC with the 8-point or 5-point algorithms, since in practice outliers are to be expected in the matching process.

I think the main downside of pose from homography is that the point matches you use need to be coplanar. Additionaly, if I'm not mistaken, in a scene with more than one plane, you might get different homographies depending on which planes you select in the scene. That is why applying a homography to correct perspective adds distortion to some other parts of the image (see the example in this video). So in complex scenes (e.g. urban environements) where matching is more difficult, I'd use one of the 8-point or the 5-point algorithms.

Note that you can also recover the relative pose directly (up to scale, obviously), and compute the essential from that (see this paper). It's easier than computing the fundamental/essential and then extracting relative pose.

Upvotes: 1

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