sample_object_model_3d — Sample a 3D object model.
sample_object_model_3d creates a sampled version of the 3D object model ObjectModel3D which consists of points that have the minimum distance SampleDistance to each other. The created 3D object model is returned in SampledObjectModel3D.
Using sample_object_model_3d is recommended if complex point clouds are to be thinned out for faster postprocessing or if primitives are to be converted to point clouds. Note that if the 3D object model is triangulated and should be simplified by preserving its original geometry as good as possible, simplify_object_model_3d should be used instead.
If the input object model ObjectModel3D contains only points, several sampling methods are available which can be selected using the parameter Method.
The default method 'fast' adds all points from the input model which are not close to any point that was earlier added to the output model. If present, normals, XYZ-mapping and extended point attributes are copied to the output model.
The method 'fast_compute_normals' selects the same points as the method 'fast', but additionally calculates the normals for all points that were selected. For this, the input object model must either contain normals, which are copied, or it must contain a XYZ-mapping attribute from which the normals are computed. The XYZ-mapping is created by xyz_to_object_model_3d.
The method 'accurate' goes through the points of the 3D object model ObjectModel3D and calculates whether any other points are within a sphere with the radius SampleDistance around the examined point. If there are no other points, the original point is stored in SampledObjectModel3D. If there are other points, the center of gravity of these points (including the original point) is stored in SampledObjectModel3D. This procedure is repeated with the remaining points until there are no points left. Extended attributes of the input 3D object model are not copied, but normals and XYZ-mapping are copied. For this method, a noise removal is possible by specifying a value for 'min_num_points' in GenParamName and GenParamValue, which removes all interpolated points that had less than the specified number of neighbor points in the original model.
The method 'accurate_use_normals' requires normals in the input 3D object model and interpolates only points with similar normals. The similarity depends on the angle between the normals. The threshold of the angle can be specified in GenParamName and GenParamValue with 'max_angle_diff'. The default value is 180 degrees. Additionally, outliers can be removed as described in the method 'accurate', by setting the generic parameter 'min_num_points'.
If the input object model contains faces (triangles or polygons) or is a 3D primitive, the surface is sampled with the given distance. In this case, the method specified in Method is ignored. Note that planes and cylinders must have finite extent. If the input object model contains lines, the lines are sampled with the given distance.
The sampling process approximates surfaces by creating new points in the output object model. Therefore, any extended attributes from the input object model are discarded.
For mixed input object models, the sampling priority is (from top to bottom) faces, lines, primitives and points, i.e., only the objects of the highest priority are sampled.
The parameter SampleDistance accepts either one value, which is then used for all 3D object models passed in ObjectModel3D, or one value per input object model. The unit of the sample distance is the usual HALCON-internal unit 'm'.
Note that if a 3D object model is no longer needed or should be overwritten, the memory has to be freed first by calling the operator clear_object_model_3d.
Handle of the 3D object model to be sampled.
Selects between the different subsampling methods.
Default value: 'fast'
List of values: 'accurate', 'accurate_use_normals', 'fast', 'fast_compute_normals'
Number of elements: SampleDistance == 1 || SampleDistance == ObjectModel3D
Default value: 0.05
Names of the generic parameters that can be adjusted.
Default value: 
List of values: 'max_angle_diff', 'min_num_points'
Values of the generic parameters that can be adjusted.
Default value: 
Suggested values: 1, 2, 5, 10, 20, 0.1, 0.25, 0.5
Handle of the 3D object model that contains the sampled points.
Number of elements: SampledObjectModel3D == ObjectModel3D
gen_box_object_model_3d ([0,0,0,0,0,0,0],3,2,1, ObjectModel3D) sample_object_model_3d (ObjectModel3D, 'fast', 0.05, , , \ SampledObjectModel3D) dev_get_window (WindowHandle) visualize_object_model_3d (WindowHandle, SampledObjectModel3D, \ , , , , , , , PoseOut)
sample_object_model_3d returns 2 (H_MSG_TRUE) if all parameters are correct. If necessary, an exception is raised.
read_object_model_3d, gen_plane_object_model_3d, gen_sphere_object_model_3d, gen_cylinder_object_model_3d, gen_box_object_model_3d, gen_sphere_object_model_3d_center, xyz_to_object_model_3d