Surface Cutting

SurfaceMeshCutter

Given a surface mesh and a set of edges, this utility class will perform cuts along the prescribed edges, disconnecting their two adjacent faces.

Usage

cutter = SurfaceMeshCutter(mesh)
cutter.cut(edge_list)

or

cutter = SurfaceMeshCutter(mesh)(edge_list) # directly calls cut

Bases: Worker

Parameters:

Name	Type	Description	Default
mesh	SurfaceMesh	input mesh	required
verbose	bool	verbose mode. Defaults to False.	False

Attributes:

Name	Type	Description
cut_edges	set	indices of edges that were cut
cut_mesh	SurfaceMesh	a copy of the mesh where specified edges have been cut

cut_graph property

The graph formed by all cut edges as a Polyline object

Returns:

Name	Type	Description
PolyLine	PolyLine	the cut graph

cut(edges_to_cut)

Cut the mesh. Alias for SurfaceMeshCutter.run

duplicated_vertices(v)

Given the index v of a vertex in the input mesh, returns the set of all copies of v in the cut mesh.

Parameters:

Name	Type	Description	Default
v	int	index of a vertex in the input mesh	required

Returns:

Type	Description
set	set[int]: all vertex indices corresponding to copies of v in the cut mesh

ref_vertex(v_cut)

Given the index v_cut of a vertex in the cut mesh, returns the index of the corresponding vertex in the original mesh.

Parameters:

Name	Type	Description	Default
v_cut	int	index of a vertex in the cut mesh. If the index is invalid, returns None	required

Returns:

Name	Type	Description
int	int	index of the reference vertex in the original mesh

run(edges_to_cut)

Cut the mesh. Fills the attributes and builds cut_mesh, which is a copy of the input mesh with corresponding edges disconnected

Parameters:

Name	Type	Description	Default
edges_to_cut	Iterable	containers of all the indices of edges to be cut	required

SingularityCutter

Given some indices in the mesh, performs cuts on the same so that:
1) every prescribed vertex becomes a boundary vertex
2) the final mesh has disk topology.

This utility class allows to define the discontinuities of a seamless global parametrization and go back and forth between the original mesh and the cut mesh.

Three strategies for computing the cuts are available:
- (A) Simple strategy: no heuristics. Computes a valid seam graph with no geometrical consideration.
- (B) Shortest path strategy: tries to minimize the total length of seams by encouraging cuts to follow shortest paths between singularities.
- (C) Follow features strategy: minimize the number of seam edges that do not belong to the feature graph (i.e. sharp edges) of the model. Requires to first run a FeatureEdgeDetector on the mesh.

Illustration of the three cutting strategies

Usage

cutter = SingularityCutter(mesh, indices, strategy="shortest")
cutter.run()

Bases: SurfaceMeshCutter

Parameters:

Name	Type	Description	Default
mesh	SurfaceMesh	input mesh	required
singularities	list	indices of the singular vertices	required
strategy	str	which strategy to use. Choices are ["simple", "short", "feat"]	'simple'
verbose	bool	verbose mode. Defaults to False.	False

Other Parameters:

Name	Type	Description
features	FeatureEdgeDetector	feature edge data structure. If provided, the cuts will follow the feature as much as possible. Defaults to None.
debug	bool	debug mode. Computes additionnal outputs as mesh attributes. Defaults to False

Attributes:

Name	Type	Description
cut_edges	set	indices of edges that were cut
cut_mesh	SurfaceMesh	a copy of the mesh where specified edges have been cut

cut_graph property

The graph formed by all cut edges as a Polyline object

Returns:

Name	Type	Description
PolyLine	PolyLine	the cut graph

duplicated_vertices(v)

Given the index v of a vertex in the input mesh, returns the set of all copies of v in the cut mesh.

Parameters:

Name	Type	Description	Default
v	int	index of a vertex in the input mesh	required

Returns:

Type	Description
set	set[int]: all vertex indices corresponding to copies of v in the cut mesh

ref_vertex(v_cut)

Given the index v_cut of a vertex in the cut mesh, returns the index of the corresponding vertex in the original mesh.

Parameters:

Name	Type	Description	Default
v_cut	int	index of a vertex in the cut mesh. If the index is invalid, returns None	required

Returns:

Name	Type	Description
int	int	index of the reference vertex in the original mesh

run()

Runs the cutting process