Surface Feature Detection

Detecting feature edges of a surface mesh is done in mouette in the FeatureEdgeDetector class. This class encapsulates various strategies of detection and stores the result for a given mesh.

Usage

fed = FeatureEdgeDetector([options])
fed.detect(mesh)

or

fed = FeatureEdgeDetector([options])(mesh) # directly calls detect

This fills the various container attributes that can be accessed in the FeatureEdgeDetector class.

Feature edge detection on CAD models

FeatureEdgeDetector(only_border=False, flag_corners=True, corner_order=4, compute_feature_graph=True, verbose=True)

Bases: Worker

Worker used to detect features on a surface mesh. Feature edges are of three types:

• Marked edges from the input file (reading the "hard_edges" attribute on edges)

• Boundary edges

• Edges such that their dihedral angle is large (crease edges)

The FeatureEdgeDetector object ican be given as a parameter in parametrization or frame field algorithms that need feature edge alignment.

Parameters:

Name	Type	Description	Default
only_border	bool	If set to True, will only consider border edges as features. Defaults to False.	False
flag_corners	bool	If set to True, will also compute a goal angle defect (multiple of pi/2) of each detected vertices. Defaults to True.	True
corner_order	int	For corner detection, considers corners of angle defect 2pi/corner_order. Defaults to 4 (corners of pi/2).	4
compute_feature_graph	bool	whether to compute a Polyline object representing the feature graph. For debug and visualization purposes. Defaults to True.	True
verbose	bool	Verbose mode. Defaults to True.	True

Attributes:

Name	Type	Description
feature_vertices	set	indices of the vertices that are adjacent to at least one feature edge
feature_edges	set	indices of feature edges
feature_degree	Attribute	number of feature edges each vertex is adjacent to
local_feat_edges	dict	features edges in the neighborhood of each vertex (in the order of mesh.connectivity.vertex_to_edges)
corners	Attribute	the order of each detected vertex corners

feature_graph property

the feature edges as a polyline object

_add_hard_edges_to_features(mesh, feature_attr)

The mesh may already define a set of "hard" edges, for instance if it was imported from a file where edges were specified. These edges should be registered as features, but we filter them if their curvature is too small.

Parameters:

Name	Type	Description	Default
feature_attr	Attribute	the feature flag to fill in	required

Returns:

Name	Type	Description
Attribute	Attribute	the modified feature flag

_add_sharp_angles_to_features(mesh, feature_attr)

Flags as features all edges which dihedral angle is smaller than pi/2 or greater than 3*pi/2

Parameters:

Name	Type	Description	Default
feature_attr	Attribute	the feature flag to fill in	required

Returns:

Name	Type	Description
Attribute	Attribute	the modified feature flag

_compute_feature_graph(mesh)

Computes self._feature_mesh

clear()

Clears the data structures

detect(mesh)

Runs the detection on a provided mesh.

Parameters:

Name	Type	Description	Default
mesh	SurfaceMesh	the input mesh	required