Biosystems Engineering Blog (Posts about linux)

Getting Started with FreeCAD Development in Ubuntu 16.04

Kurt Kremitzki — Sun, 05 Jun 2016 11:17:51 GMT

FreeCAD is a multi-platform (Windows, Mac, Linux) open source parametric 3D CAD modeler, and can read and write many open file formats.

An explanation of the many virtues of open source software can be found at Open Source for America and elsewhere. To quote OSFA,

The Open Source model harnesses the power of distributed peer review and transparency to create high-quality, secure and easily integrated software at an accelerated pace and lower cost.

Commerical-grade CAD software, while incredibly useful, has several downsides including being locked behind 4 or 5 digit licensing costs, and its use in amateur projects or the developing world is often facilitated by piracy. FreeCAD, on the other hand, is free as in beer and free as in freedom, although it is currently under development. However, one of the benefits of the open source model is the ease with which interested people can contribute to the project and make better tools for all mankind.

While using FreeCAD, I noticed a few typos in the menus; although my first contribution to the project wasn't too significant, I documented the process of getting a development environment set up on my Ubuntu 16.04 desktop so that others could follow the same steps and begin contributing.

Pull down a copy of the code. (If you don't have a copy of git, run sudo apt-get install git.)

git clone https://github.com/FreeCAD/FreeCAD.git freecad-code
mkdir freecad-build

Install all dependencies.

sudo apt-get install build-essential cmake python python-matplotlib libtool libcoin80-dev \
  libsoqt4-dev libxerces-c-dev libboost-dev libboost-filesystem-dev libboost-regex-dev  \
  libboost-program-options-dev libboost-signals-dev libboost-thread-dev libboost-python-dev \
  libqt4-dev libqt4-opengl-dev qt4-dev-tools python-dev python-pyside pyside-tools 'liboce*-dev' \
  oce-draw libeigen3-dev libqtwebkit-dev libshiboken-dev libpyside-dev libode-dev swig libzipios++-dev \
  libfreetype6 libfreetype6-dev

# Install optional packages
sudo apt-get install libsimage-dev checkinstall python-pivy python-qt4 doxygen \
  libcoin80-doc libspnav-dev

Move into build folder, make and compile the software. Use the -j $(nproc) flag to use all N of your CPU cores when compiling; some recommend using N + 1 CPU cores, which can be done by instead running make -j$(( $(nproc) + 1 )) .. Don't forget the period at the end of the make command, which tells it to put the compiled software in the current freecad-build directory; it's good to keep the source code and build directories separate.

cd freecad-build
cmake ../freecad-code
make -j$(nproc) .

Fix Ubuntu 64-bit issue. If you are using a 64-bit version of Ubuntu (hopefully), you may run in to the following error message, which occurs because the expected libfreeimage.so file was moved into a subdirectory of /usr/lib/.

make[2]: *** No rule to make target '/usr/lib/libfreeimage.so', needed by 'lib/libSMDS.so'.  Stop.

# Fix with this line.
sudo ln -s /usr/lib/x86_64-linux-gnu/libfreeimage.so /usr/lib

Once the build is complete, a runnable copy of the FreeCAD executable will be in the freecad-build folder. Any changes made to the source code can be tested after re-compiling the executable.

Hopefully this post helps someone out there! Even if you are only contributing to the documentation as you learn FreeCAD, your contribution is valuable and can help tons of people across the globe.

Linux Console Caps/Escape Swap

Kurt Kremitzki — Wed, 18 May 2016 03:40:12 GMT

Full-fledged Linux desktop environments like GNOME or Ubuntu's Unity often have built-in keyboard mapping tools to meet user needs. At a lower level, xmodmap can be used to directly modify the X11 server's keyboard mapping. However, when working directly in the Linux console, things are a little more complicated without a display server.

My particular need is to swap the Caps Lock and Escape keys; as a vim user, I use Escape constantly to return to Normal mode. To be more efficient and avoid the possibility of repetitive strain injury from long-term pinky stretching to reach Escape, the following line can be added to the file /etc/rc.local, before the final line exit 0.

/usr/bin/dumpkeys | /bin/sed 's/CtrlL_Lock/Escape/' | /usr/bin/loadkeys

If you aren't familiar with Bash, a little explanation might be in order. First, note that this single-line command is actually three commands separated by the pipe character |. A detailed explanation can be found in the Advanced Bash Scripting Guide's chapter on I/O Redirection, but in short, piping cmd1 | cmd2 sends the output of cmd as input for cmd2.

The programs /usr/bin/dumpkeys and /usr/bin/loadkeys are fairly self-explanatory: they output keymaps for the console at the kernel level, and update that keymap if a valid file is input, respectively. The middle command, sed, is a powerful, general-purpose stream editor, and the source of much Linux wizardry. To understand what it's doing, take a look at its argument: the string '/s/CtrlL_Lock/Escape/'. This tells sed to s ubstitute the first instance of CtrlL_Lock with Escape on any matching line from its input (adding g after the last slash makes it a truly global substitution and not linewise.) The sed command then passes along the modified stream to loadkeys. Because this line is added to /etc/rc.local, it will be executed every boot, swapping Caps Lock and Escape in the Linux console.

Keeping zoom level when navigating PDF in Evince, GNOME's Document Viewer

Kurt Kremitzki — Sun, 24 Apr 2016 21:51:08 GMT

This one is short, sweet, and to the point. How often do you have your PDF set to a nice zoom level, only to have it reset when navigating via the Bookmarks/Index? If you use GNOME as a Linux DE (desktop environment), then you can fire up a terminal and use this gsettings one-liner to preserve zoom:

gsettings set org.gnome.Evince allow-links-change-zoom false

A great alternative PDF reader is the vim-key friendly zathura. I've had issues opening larger PDFs with it though, so your mileage may vary.

Connecting a Raspberry Pi to Texas A&M Wifi via Command Line

Kurt Kremitzki — Thu, 21 Apr 2016 23:46:17 GMT

The recommended flavor of Linux on the Raspberry Pi, Raspbian, uses the LXDE desktop environment, and using its GUI tools to set up wifi is not immediately successful. Command-line setup involves editing two files, /etc/network/interfaces and /etc/wpa_supplicant/wpa_supplicant.conf. Since these are system files, they won't be writable by a normal user. The command sudo -e <filename> can be used to edit system files with superuser privileges, using the default editor. Normally, this is the program nano, which is fairly self-explanatory; make your changes using the keyboard and save the file with Ctrl-X. For advanced users, this can be changed via something like export EDITOR=vi.

The first file, /etc/network/interfaces, needs to have the following: