Linear Algebra Tools

Wednesday | Friday
Fall 2018

Linear Algebra Tools

For additional reading on this topic in the context of computer graphics, I recommend Immersive Linear Algebra, particularly the first four chapters. Some content covered at the site we will not be using now, but will likely revisit later when we move to 3D. For now, it is sufficient to review the topics we cover in class and skip the rest.

You should also read the sections in the learn OpenGL tutorial on Vector and Matrix prelims, and Coordinate Systems. Again, the tutorial uses slightly different syntax since it uses GLM, an OpenGL math library similar to GLSL for C++ (GLSL runs on the GPU, not the CPU), while we will primarily be using the Qt5 classes QVector3D and QMatrix4x4. However, the coordinate frames, ideas, and transformations discussed are identical.

Adding Git Remotes

Let's try this again.

The examples repo should have two remotes. The first, origin, refers to your personal copy on the github server. The second, upstream, refers to a read-only copy that I will update throughout the semester. Let's check the status of our remotes and get some updates

$ cd ~/cs40/examples
$ git remote show

If you do not have an upstream remote, you can add it now.

git remote add upstream
git fetch upstream

$ git remote show origin
X11 forwarding request failed on channel 0
* remote origin
  Fetch URL:
  Push  URL:
  HEAD branch: master
  Remote branches:
    master tracked
  Local branches configured for 'git pull':
    master merges with remote master
  Local refs configured for 'git push':
    master pushes to master (up to date)

$ git remote show upstream
X11 forwarding request failed on channel 0
* remote origin
  Fetch URL:
  Push  URL:
  HEAD branch: master
  Remote branches:
    master tracked

$ git branch -avv

 master                  ddee7fe [origin/master] Last commit message
 remotes/origin/HEAD     -> origin/master
 remotes/origin/master   ddee7fe Last commit message
 remotes/upstream/master 19169f2 upstream commit message

Try to get the latest changes from upstream
git fetch upstream
git merge upstream/master
fatal: refusing to merge unrelated histories

Let's fix the issue of unrelated histories by forcing the merge, but keeping any of our local changes.

git merge -X ours --allow-unrelated-histories upstream/master

After this step, you will need to manually edit the top level CMakeLists.txt to add the new subdirectories.

$ tail ~/cs40/examples-adanner1/CMakeLists.txt

# add these two lines

If everything went well, you should be able to go into your build directory and run make -j8 to compile the week 02 and 03 samples.

cd build
make -j8
cd w03-cube

The x,y, and z keys allow you to rotate the cube. It's kind of hard to tell it's a 3D cube at this point. We'll be working on that in the next few weeks.

Configuring your git editor

Often after a merge, git will drop you into an editor to edit the commit message. For some of you the default editor may be the dreaded vim. To accept the default message and quit vim, type <ESC> :wq. To change your editor, you can use git config --global core.editor and some editor. For atom users, you can use, e.g.,

git config --global core.editor "atom --wait"