Updating orbslam3 v1 support

[matlabbe]

Address #886

Current issues when enabling IMU (tested with Realsense2 D435i):

• Seg fault here when ORB_SLAM3 is built in Release mode: https://github.com/UZ-SLAMLab/ORB_SLAM3/blob/4452a3c4ab75b1cde34e5505a36ec3f9edcdc4c4/src/Optimizer.cc#L831
  • Workaround: build ORB_SLAM3 in Debug mode.
• Got Solving Sophus -nan error UZ-SLAMLab/ORB_SLAM3#608, tried Solving Sophus -nan error UZ-SLAMLab/ORB_SLAM3#608 (comment) but ORB_SLAM3 is always resetting...

TODO:

• Expose IMU parameters
• Make sure ORB_SLAM2 version still work after refactoring

Changes made upstream (ORB_SLAM3) to work on Ubuntu 20.04:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 016e743..5321227 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,9 +14,15 @@ set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -march=native")
 
 # Check C++11 or C++0x support
 include(CheckCXXCompilerFlag)
+CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
 CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
 CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
-if(COMPILER_SUPPORTS_CXX11)
+if(COMPILER_SUPPORTS_CXX14)
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
+   add_definitions(-DCOMPILEDWITHC14)
+   add_definitions(-DCOMPILEDWITHC11)
+   message(STATUS "Using flag -std=c++14.")
+elseif(COMPILER_SUPPORTS_CXX11)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
    add_definitions(-DCOMPILEDWITHC11)
    message(STATUS "Using flag -std=c++11.")
@@ -30,9 +36,9 @@ endif()
 
 LIST(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake_modules)
 
-find_package(OpenCV 4.4)
+find_package(OpenCV 4.2)
    if(NOT OpenCV_FOUND)
-      message(FATAL_ERROR "OpenCV > 4.4 not found.")
+      message(FATAL_ERROR "OpenCV >= 4.2 not found.")
    endif()
 
 MESSAGE("OPENCV VERSION:")

[matlabbe]

Related issues:
#655
#1104