在PnP后进行BA优化和使用G2O中所遇到的问题总结

1. 问题：target_compile_features specified unknown feature “cxx_std_14” for target "core"
解决方案：cmake版本需要3.3以上，我选择3.3.15cmake通过

cmake地址：https://cmake.org/files(找到最新版)

执行 :
tar xvf  cmake-3.15.0.tar.gz


找到cmake文件并卸载
不能直接sudo apt remove --purge cmake
locate cmake //在usr路径下删除cmake的文件

之后进行:
./configure
make -j8
sudo make install
cmake --version//查看安装版本

2.问题：error: ‘index_sequence’ is not a member of 'std’
解决方法：所以需要把CMakeLists.txt文件中改为C++14编译。

将
set( CMAKE_CXX_FLAGS "-std=c++11" )
改成
set( CMAKE_CXX_FLAGS "-std=c++14" )

3.问题 error: ‘VertexSBAPointXYZ’ is not a member of ‘g2o’
解决方案：

新版g2o库中不再存在原先的VertexSBAPointXYZ，将所有报错的地方改为VertexPointXYZ即可：

或者是

g2o 20200410_git版本也可以解决，该版本使用VertexSBAPointXYZ这个
https://github.com/RainerKuemmerle/g2o/archive/refs/tags/20200410_git.zip

4.问题 usr/local/include/g2o/core/base_fixed_sized_edge.hpp:166:14: error: ‘FixedArray {aka class ceres::internal::FixedArray}’ has no member named ‘fill’ add_vertex.fill(0.); /usr/local/include/g2o/core/base_fixed_sized_edge.hpp:173:30: error: ‘FixedArray {aka class ceres::internal::FixedArray}’ has no member named ‘data’ vertex->oplus(add_vertex.data());

解决方案：因为新版本不兼容问题，需要将g2o版本换成 20200410_git版本， 
https://github.com/RainerKuemmerle/g2o/archive/refs/tags/20200410_git.zip

5. 问题 DSO missing的原因基本上是因为有库没有连接上，导致未识别。最保险的方法是在最前端将所有库设置为G2O_LIBS：还有所用到的头文件名称

头名称：

#include  
#include 
// #include 
#include 
#include 
#include 
// #include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include  

cmakelist.txt

include(cmake/FindG2O.cmake)
include(cmake/FindCSparse.cmake) 

include_directories(
  cmake
 
  ${OpenCV_INCLUDE_DIRS}
  ${EIGEN3_INCLUDE_DIR} 
 
  ${Sophus_INCLUDE_DIRS} 
  ${CSPARSE_INCLUDE_DIR} 
)


target_link_libraries(project_name  #工程名称
 
  ${catkin_LIBRARIES}
  ${OpenCV_LIBS} fmt
  ${EIGEN3_LIBS}
  ${EIGEN_DEFINITIONS}
  ${Sophus_LIBRARIES}
  g2o_core g2o_stuff g2o_types_sba g2o_csparse_extension g2o_types_slam3d
  ${CSPARSE_LIB}
)