Going VR – What to expect next on this Blog

During the ongoing year, this blog will present some of my private projects and research in the area of computer vision and virtual reality. My private interests and research activity are currently in the area of computer vision including photogrammetry and visual odometry (as part of my phd thesis). Besides some off-topic posts, my blog will also reflect this personal development.
From time to time, I will post some news on my private projects on this website. You are invited to comment and share your thoughts. Some project ideas for the coming months are:

  • Experiments for inside out tracking of cardboard based VR-devices
  • An IMU-Mocap Suite
  • and maybe some haptic devices like a VR windmachine.

My main focus lies on the research for my phd thesis, even though updates will be more regular than during the past months (but will not be postet on a predefined schedule).

Looking forward to get in touch with you again,

Most used GIT commands (at least for me :) )

git log
Shows the log of all previous commits of the selected branch

git log –stat
Shows some statistics about the commits of the active branch

git log –graph
Shows information about the branch history of a branch or commit

checkout COMMITID
Jumps to the selected commit with the given ID

Jumps to the selected commit with the given ID

Compares commit with ID COMMITID1 against commit with ID COMMITID2

git add FILENAME
Stages the named file

git commit
Commits the staged files to the repository

git commit -m “MESSAGE

Adds the message to the staged commit

git show COMMITID
Compares a commit against its parent

git branch
Shows all branches of the current repository

git branch BRANCHNAME
Created new branch in the repository with the given name

git branch -d BRANCHNAME
Deletes the branch with name BRANCHNAME from the repository

Merges the branches with name BRANCHNAME1 and BRANCHNAME2

git reset –hard
Throws all uncomitted changes away

git remote add REMOTENAME GITURL

git remote -v
Outputs additional information to the remotes

Pushed the changes to the remote

Pulls the changes from the remote

git fetch
Updates the origin/master branch from the remote repository

git pull origin master
Same as: 1. git fetch origin 2. git merge master master/origin

NVIDIA driver and Ubuntu: How to fix blackscreen after kernel update!

If you use the Nvidia driver and updated your kernel, it’s possible that you run into a blackscreen after boot.
There are two solutions to solve this issue:

Solution 1:
1. Boot into GRUB by pressing “shift” during boot.
2. Edit the starting command by pressing “e“.
3. Add “nomodeset” before “quiet splash“.
4. Press “Ctrl-x” to boot.
You should now see the GUI and be able to reinstall the Nvidia driver correctly.
5. Disable lightdm and reinstall the Nvidia driver.

Solution 2:
If the solution above didn’t work for you, try these steps:
1. Boot into GRUB by pressing shift during boot.
2. Chose the recovery mode.
3. Choose “root” to go into the root shell
4. To leave read only mode enter “mount -o remount,rw /”
5. Remove all installed nvidia packages using “sudo apt-get remove –purge nvidia-*”
6. Continue following the stept mentioned at solution 1.

NVIDIA and libfreenect2: How to fix undefined reference to ‘clReleaseDevice’ and ‘clRetainDevice’

Because AMD and Nvidia provide different versions of the OpenCL header, the following error can occur compiling a program using libfreenect2 and a Nvidia GPU.

/usr/local/lib/libfreenect2.so: undefined reference to `clReleaseDevice'
/usr/local/lib/libfreenect2.so: undefined reference to `clRetainDevice'

This error can be fixed by installing:

sudo apt-get install ocl-icd-opencl-dev

After the installation, the undefined reference should be fixed.

Update: If the problem occurs compiling a catkin package, it might be solved by reinitializing the catkin workspace.