execute_context(CONTEXT_TERRAIN); //draw some things

        get_backbuffer(&backbuffer);
        backbuffer.writeToTIFF("terrain.tif"); //write backbuffer to a file

        glClearColor(0.0,0.0,0.0,0.0);
        glClear(GL_COLOR_BUFFER_BIT);
        glFlush();

        execute_context(CONTEXT_SYMBOLS); //draw some other things

        get_backbuffer(&backbuffer);
        backbuffer.writeToTIFF("annotaions.tif"); //write backbuffer to a file