geometric_shapes package fails to process, assimp/aiScene.h not found

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I'm running OS X 10.9.4 on the latest MacBook Pro, with gcc 4.9.1 installed via homebrew. Currently trying to set up the full Indigo installation. I've followed the official instructions to do this (Installation/OSX/Homebrew/Source), but have hit something of a roadblock with the following:

$ ./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release

I've had a poke around on the internet but can't seem to work out what the problem is - the last time a similar issue came up here (question 156916) it appears to have been solved by updating to the newest version of geometric_shapes, but I have never had ROS on this machine before, so I don't see how this could be caused by the same thing.

Here's the terminal output showing what happened with geometric_shapes:

==> Processing catkin package: 'geometric_shapes'
==> Building with env: '/Users/Thomas/ros_catkin_ws/install_isolated/env.sh'
Makefile exists, skipping explicit cmake invocation...
==> make cmake_check_build_system in '/Users/Thomas/ros_catkin_ws/build_isolated/geometric_shapes'
==> make -j8 -l8 in '/Users/Thomas/ros_catkin_ws/build_isolated/geometric_shapes'
[ 20%] Building CXX object CMakeFiles/geometric_shapes.dir/src/mesh_operations.cpp.o
/Users/Thomas/ros_catkin_ws/src/geometric_shapes/src/mesh_operations.cpp:54:10: fatal error: 
  'assimp/aiScene.h' file not found
#include <assimp/aiScene.h>
         ^
1 error generated.
make[2]: *** [CMakeFiles/geometric_shapes.dir/src/mesh_operations.cpp.o] Error 1
make[1]: *** [CMakeFiles/geometric_shapes.dir/all] Error 2
make: *** [all] Error 2
<== Failed to process package 'geometric_shapes': 
Command '/Users/Thomas/ros_catkin_ws/install_isolated/env.sh make -j8 -l8' returned non-zero exit status 2

Reproduce this error by running:
==> cd /Users/Thomas/ros_catkin_ws/build_isolated/geometric_shapes && /Users/Thomas/ros_catkin_ws/install_isolated/env.sh make -j8 -l8

Command failed, exiting.

I would be grateful for any help, thanks in advance :)