Modify CMakeLists to use openMVG on other project

[aiqu]

1. Fix stlplus3 CMakeLists to generate proper include paths
2. Add & export dependencies/cereal to openMVG-targets
3. Add & export header only third_party folders to openMVG-targets

While I'm using openMVG in my project, I suffered a lot of troubles especially related to include paths.
This pr mainly focused on proper include path configuration.

Also, it should update dependencies/cereal submodule, too.
So, I'll create the corresponding pr to that repo.

Since I just learned about modern CMake, let me know if I misunderstood your intention.

[aiqu]

This pr requires below.

Related pr on cereal.
openMVG-thirdparty/cereal#1

[pmoulon]

ceresl is already linked in openMVG_camera so you do need to add it there.

[aiqu]

Got it, I'll remove cereal from openMVG_camera_test

[pmoulon]

Can you explain why you need this?

[aiqu]

At first, I want to declare every third-party utility explicitly so it gives more modularity.
However, just adding 'include/openMVG' to OPENMVG_INCLUDE_DIRS would be enough.

[pmoulon]

We need to do this only if we use the internal cereal. Please note that OpenMVG can use an external cereal library.
Can you check that your modification will work even you are using an external cereal library.

[aiqu]

Got it.

[pmoulon]

Thx you.
Can you give you a typical main.cpp and CMakeLists.txt that you are using to check and show that the existing CMake code was not working for your purpose.

[pmoulon]

FYI, your changes are not working on VisualStudio CI: https://ci.appveyor.com/project/pmoulon/openmvg/build/1.0.861
Neither on GCC, Clang and XCode CI:
https://travis-ci.org/openMVG/openMVG/builds/350919601

[aiqu]

Example

• CMakeLists.txt

CMAKE_MINIMUM_REQUIRED(VERSION 3.0)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

find_package(OpenMVG REQUIRED)
find_package(Eigen3 REQUIRED)

add_executable(main main.cpp)
target_include_directories(main PUBLIC
  ${OPENMVG_INCLUDE_DIRS}
  ${EIGEN3_INCLUDE_DIRS}
)
target_link_libraries(main PUBLIC
  ${OPENMVG_LIBRARIES}
)

• main.cpp

// To use cereal input/output function
#include <cereal/archives/json.hpp>
// No use case in this example, but requires in particular cases.
// Moreover, since this header is exposed to user, I think it should be included properly
#include <openMVG/graph/graph.hpp>
// It uses progress utility.
#include <openMVG/sfm/pipelines/sfm_features_provider.hpp>
#include <openMVG/features/image_describer.hpp>
#include <memory>

int main() {
  std::ifstream file("test.json");
  std::shared_ptr<openMVG::features::Image_describer> desc;
  cereal::JSONInputArchive archive(file);

  return 0;
}

• Encountered errors on branch develop
  1. fatal error: cereal/archives/json.hpp: No such file or directory
  2. fatal error: lemon/connectivity.h: No such file or directory
  3. fatal error: third_party/progress/progress_display.hpp: No such file or directory

[pmoulon]

I will look to your PR.
Happy to see that the Travis CI is ok.

FYI: According the last change those lines should not be required:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
find_package(OpenMVG REQUIRED)
find_package(Eigen3 REQUIRED)
target_include_directories(main PUBLIC
  ${OPENMVG_INCLUDE_DIRS}
  ${EIGEN3_INCLUDE_DIRS}
)

All the includes and compilation flags should be added by:

target_link_libraries(main PUBLIC
  ${OPENMVG_LIBRARIES}
)