create_deformable_surface_model — Create the data structure needed to perform deformable surface-based matching.
The operator create_deformable_surface_model creates a model for deformable surface-based matching for the 3D object stored in the 3D object model ObjectModel3D. The 3D object model can, for example, have been read previously from a file by using read_object_model_3d or it can have been created by using xyz_to_object_model_3d. The created surface model is returned in DeformableSurfaceModel.
The creation of the deformable surface model requires that the 3D object model contains points and normals. The following combinations are possible:
points and point normals, e.g., from a call to surface_normals_object_model_3d
points and a triangular or polygon mesh, e.g., from a CAD file
points and a 2D-Mapping, e.g., from an XYZ image triple converted with xyz_to_object_model_3d
Note that the direction and orientation (inward or outward) of the normals of the model are important for matching.
The deformable surface model is created by sampling the 3D object model with a certain distance. The sampling distance must be specified in the parameter RelSamplingDistance and is parametrized relative to the diameter of the axis-parallel bounding box of the 3D object model. For example, if RelSamplingDistance is set to 0.05 and the diameter of ObjectModel3D is 10 cm, the points sampled from the object's surface will be approximately 5 mm apart. The sampled points can be obtained with the operator get_deformable_surface_model_param using the value 'sampled_model'. Note that outlier points in the object model should be avoided, as they would corrupt the diameter. Reducing RelSamplingDistance leads to more points, and in turn to a more stable but slower matching. Increasing RelSamplingDistance leads to less points, and in turn to a less stable but faster matching.
By default, deformable surface models created with create_deformable_surface_model can handle a moderate amount of deformation. The operator add_deformable_surface_model_sample can be used to add additional training samples, thus expanding the range of possible deformations. The amount of deformation that can be found can also be controlled with the generic parameters 'scale_min', 'scale_max' and 'bending_max' (see below).
The generic parameter pair GenParamName and GenParamValue is used to set additional parameters for the model generation. GenParamName contains the tuple of parameter names that shall be set and GenParamValue contains the corresponding values. The following values are possible for GenParamName:
Invert the orientation of the surface normals of the model. The normal orientation needs to be known for the model generation. If both the model and the scene are aquired with the same setup, the normals will already point in the same direction. If the model was loaded from a CAD file, the normals might point into the opposite direction. If you experience the effect that the model is found on the 'outside' of the scene surface and the model was created from a CAD file, try to set this parameter to 'true'. Also, make sure that the normals in the CAD file all point either outward or inward, i.e., are oriented consistently.
Possible values: 'false', 'true'
Default value: 'false'
The minimum and maximum allowed scaling of the model. Note that if you set one of the two parameters, the other one must be set too.
Suggested values: 0.8, 1, 1.2
Default value: No scaling
Assertion: 0 < 'scale_min' < 'scale_max'
Controls the maximum automatic deformation of the model. The model is deformed automatically by bending it with an angle up to the value of 'bending_max'. This allows for deformations to be found that are within this bending range. The angle is passed in degrees.
Suggested values: 5, 10, 30
Default value: 20
Assertion: 0 <= 'bending_max' < 90
Control the stiffness of the model when performing the refinement. Larger values of this parameter lead to a more stiff model that can be less deformed. Smaller values lead to a less stiff model that allows more deformation.
Suggested values: 0.2, 0.5, 0.8
Default value: 0.5
Assertion: 0 < 'stiffness' <= 1
This operator returns a handle. Note that the state of an instance of this handle type may be changed by specific operators even though the handle is used as an input parameter by those operators.
Handle of the 3D object model.
Sampling distance relative to the object's diameter
Default value: 0.05
Suggested values: 0.1, 0.05, 0.03, 0.02, 0.01
Restriction: 0 < RelSamplingDistance < 1
Names of the generic parameters.
Default value: 
Suggested values: 'model_invert_normals', 'scale_min', 'scale_max', 'bending_max', 'stiffness'
Values of the generic parameters.
Default value: 
Suggested values: 'true', 'false', 1, 0.9, 1.1, 5, 10, 20, 30, 0.05, 0.1, 0.2
Handle of the deformable surface model.
create_deformable_surface_model returns 2 (H_MSG_TRUE) if all parameters are correct. If necessary, an exception is raised.
read_object_model_3d, xyz_to_object_model_3d, get_object_model_3d_params
add_deformable_surface_model_sample, add_deformable_surface_model_reference_point, find_deformable_surface_model, refine_deformable_surface_model, get_deformable_surface_model_param, write_deformable_surface_model, clear_deformable_surface_model
find_deformable_surface_model, refine_deformable_surface_model, read_deformable_surface_model, add_deformable_surface_model_sample, add_deformable_surface_model_reference_point, write_deformable_surface_model, clear_deformable_surface_model
Bertram Drost, Slobodan Ilic: “Graph-Based Deformable 3D Object Matching.” Proceedings of the 37th German Conference on Pattern Recognition, pp. 222-233, 2015.