Installing pbrt currently includes build binaries and the static library only. For compiling against pbrt library from other programs, we need the header files of pbrt.
Possible solution: change CMakeLists.txt s.t. all source header files located in ./src/ are copied to include/pbrt/ which preserves directory structure. This is done by appending
INSTALL ( DIRECTORY src/
FILES_MATCHING PATTERN "*.h"
to CMakeLists.txt. All relevant header files should be included. I locally extended it this way and it works. Further usage details: http://www.cmake.org/cmake/help/v3.2/command/install.html
Maybe I should add the following: unless I am mistaken, I think that establishing pbrt as a library to link to (from programs other than pbrt) first requires solving