gluUnProject
The gluUnProject function maps window coordinates to object coordinates.
int gluUnProject(
GLdouble winx,
GLdouble winy,
GLdouble winz,
const GLdouble modelMatrix[16],
const GLdouble projMatrix[16],
const GLint viewport[4],
GLdouble * objx,
GLdouble * objy,
GLdouble * objz
);
Parameters
winx, winy, winz
The window coordinates to be mapped.
modelMatrix
The modelview matrix (as from a glGetDoublev call).
projMatrix
The projection matrix (as from a glGetDoublev call).
viewport
The viewport (as from a glGetIntegerv call).
objx, objy, objz
The computed object coordinates.
Return Values
If the function succeeds, the return value is GL_TRUE.
If the function fails, the return value is GL_FALSE.
Remarks
The gluUnProject function maps the specified window coordinates into object coordinates using modelMatrix, projMatrix, and viewport. The result is stored in objx, objy, and objz.