Different ways to estimate relative pose during visual servoing

In order to obtain relative pose (pdHp) between current and desired pattern pose (cHp and cHpd) in camera frame, we can:

Method 1: Find rigid transformation between two set of pattern points (X_p and X_pd) in camera frame directly using a findRigidTransform() function described here.

Method 2: Calculate cHp and cHpd using the findRigidTransform() as the pattern points in local coordinate is known. The relative pose pdHp is calculated as:

pdHp = inv(cHpd) * cHp

Method 3: Calculate cHp and cHpd using the cv::solvePnP() function which finds an object pose from 3D-2D point correspondence. The relative pose is then calculated same as method 2.

According to the results, Method 1 is least stable and accurate as the estimated relative pose varies a lot and very different from the other two methods.
Method 2 and 3 have similar results in which Method 3 seems better since the rotation part is closer to Identity when the relative pose should be the same.

Summary: Method 3 is the best for the time being.

Relative trajectory playback from different starting pose

1. Given a trajectory in the global frame, a relative trajectory (H_rela) can be generated as:

H_rela = inv(H_1) * H_i

Since the relative transformation is regard to local frame (first pose in the trajectory). H_rela(1) is Identity

2. For a new starting pose in the global frame H_start, a new trajectory begins at the starting pose is generated as:

H_new = H_start * H_rela

where H_new is in the global frame.

Git - update submodule

Update and merge/rebase local submodule with upstream:

git submodule update --remote --merge

git submodule update --remote --rebase

Under main project directory, see difference of submodule:

git diff --submodule

3 cases:

• Same commit but submodule has dirty suffix

-Subproject commit c5c6bbaf616d64fbd873df7b7feecebb81b5aee7
+Subproject commit c5c6bbaf616d64fbd873df7b7feecebb81b5aee7-dirty

It means that git status in the submodule isn't clean. cd into the submodule and see what's going on.

• Different commit, former one is correct (the one in main project)

-Subproject commit c4478af032e604bed605e82d04a248d75fa513f7
+Subproject commit c79d9c83c2864665ca3fd0b11e20a53716d0cbb0

If the former is right, add and commit the new version of the submodule in main project

• Different commit, latter one is correct (the one in submodule)

If the latter is right, change the version that the submodule is at with:

git submodule update $submodule_name$

Reference:
[1] http://git-scm.com/book/en/v2/Git-Tools-Submodules
[2] http://stackoverflow.com/questions/6006494/git-submodule-modified-files-status