C/C++ : Adding Searching Include Directory

I have compiled a source code (Opendtect) using CMake. When I compile this program, the required include directory is not exist in the C/C++ searching path. Modified the Makefile is very hard, because this is the other people code.

We can copy all the include library to default C/C++ include directory (/usr/include). But, I dont recomended this. The other good method is adding searching include directory for my compiler. I get a documentation from gnu website about this :

CPATH
C_INCLUDE_PATH
CPLUS_INCLUDE_PATH
OBJC_INCLUDE_PATH
    Each variable's value is a list of directories separated by a special character, much like PATH, in which to look for header files. The special character, PATH_SEPARATOR, is target-dependent and determined at GCC build time. For Microsoft Windows-based targets it is a semicolon, and for almost all other targets it is a colon.
    CPATH specifies a list of directories to be searched as if specified with -I, but after any paths given with -I options on the command line. This environment variable is used regardless of which language is being preprocessed.
    The remaining environment variables apply only when preprocessing the particular language indicated. Each specifies a list of directories to be searched as if specified with -isystem, but after any paths given with -isystem options on the command line.
    In all these variables, an empty element instructs the compiler to search its current working directory. Empty elements can appear at the beginning or end of a path. For instance, if the value of CPATH is :/special/include, that has the same effect as ‘-I. -I/special/include’.

The GNU have some of variable to adding new Include path directory to our program. Example, if we want to add new path include directory to our C++ code, we can use a command like this :

export CPLUS_INCLUDE_PATH=$CPLUS_INCLUDE_PATH:/data/SIMVoleon/include/

We can add this command to our user path (/home/username/.bashrc) to make permanent or only use this command in current console.