A C++11-based class that performs curve fitting based on An algorithm for automatically fitting digitized curves by Philip J. Schneider which was published in Graphics gems, 1990. The algorithm is presented with minor modifications and improvements.
Although the algorithm is complete, the wrap-up project is still in development and may undergo some changes and improvements, e.g., an example of OpenGL-based visualization only will be added, as well as stl-based usage only (no Qt and OpenSceneGraph dependencies).
Currently the project requires installed OpenSceneGraph (>= 3.4.0) and C++11 compatible compiler.
Use the OsgPathFitter class or derive your own using the base PathFitter.
The PathFitter is a template abstract base class. Which means, you have to sub-class it and provide your own implementation for the pure virtual functions. The list of functions and their expected behaviour is described in the following sub-sections.
The constructor does not require any implementation, but it requires to provide a list of arguments for the used templates. In the case of OsgPathFitter, the template arguments are:
osg::Vec3Arrayis a vector of a 3D component. In the base class it has a template nameContainer.osg::Vec3fis a 3D/2D component of typefloat, i.e., given the aboveContainer = Vec3Array(Vec3f, Vec3f, ...). In the base class the template has a namePoint2D.floatis a real type of which thePoint2Dconsists of, i.e.,Vec3f(float, float, float). In the base class it has a nameReal.
It is the main loop method that launches the fitting algorithm. It is designed to be virtual and pure so that the user is able to manage the memory by smart pointers of their choice. In case of OsgPathFitter, we chose osg::ref_ptr<>.
The main steps that are needed to be in the method are:
- Allocate new
Containermemory (manage it by means of smart pointer of choice if you wish). - Calculate tangents of the extreme points as shown in the
OsgPathFitter::fit()example. - Launch method
PathFitter::fitCubic()provided a newly allocated container where the results will be saved, the tolerance error, the container's first and last point indexes, and the calculated tangent. - Return the pointer on the allocated container which will contain the result points.
Must return an Euclidean distance between two Point2Ds. Of course, depending on the dimension of your Points, the formula will vary. Refer to the provided OsgPathFitter example for more details.
Must return a Point2D with initialized values of NAN (from math.h).
In your custom class, it is necessary to provide template definitions. As it was mentioned above, you provide the definitions in the custom constructor. The full definitions must be provided at the end of your .cpp implementation file of the custom path fitter class.
The PathFitter class must also contain the full definition to avoid the LNK2019, Unresolved external symbol. For this purpose, we prepared a file called PathFitter-impl.cpp that is to contain such definitions. Note we use the separate file simple for convenience reasons so that do not add custom definitions into the PathFitter abstract class.
The PathFitter and its derivatives and compiled into a library libPathFitter so that to be easily used from an external project. In this case, you will only need to modify your project's corresponding CMakeLists.txt file. For example:
add_subdirectory(CurveFitting/libPathFitter)
link_directories(${CMAKE_BINARY_DIR}/src/libNumerics/CurveFitting/libPathFitter)
# ...
target_link_libraries( libExternal
libPathFitter
${QT_LIBRARIES}
${OPENSCENEGRAPH_LIBRARIES}
# ... any other libs
)
For a live example, feel free to refer to Cherish project and its corresponding CMakeLists.txt.
See the corresponding licence file.
On the image, 60 sampled curve (red color) is represented by a 1 cubic bezier curve (green color).
Another example that includes 3 curves representing 180 sampled path.
