Quick notes on installing Gazebo classic on MacOS. There are some instructions here for installing from source, however there are only extensive instructions for installing from source for Ubuntu and MacOS users are pointed towards brew formulas. These instructions are based on the brew formula which is linked to.
Install dependencies
brew install cmake pkg-config boost bullet dartsim doxygen ffmpeg freeimage graphviz gts ignition-common3 ignition-fuel-tools4 ignition-math6 ignition-msgs5 ignition-transport8 libtar ogre1.9 protobuf qt@5 qwt-qt5 sdformat9 simbody tbb tinyxml1 tinyxml2 urdfdom zeromq