Wire Modeling

<<< Sheet Sewing

Chapters

Enquiry and Output Functions >>>

Contents

• 37.1 Introduction
• 37.2 Creating faces to fit wire bodies
• 37.3 Blending vertices on wire bodies
• 37.4 Offsetting planar wire bodies
• 37.5 Edge orientation on wire bodies
• 37.6 Splitting a wire body
• 37.7 Creating wire bodies from curves
  • 37.7.1 Mapping edges onto originating curves
  • 37.7.2 Specifying options
• 37.8 Creating wire bodies from edges
  • 37.8.1 Specifying options

[back to top]

37.1 Introduction

Parasolid provides some specific functionality for modeling operations which can be applied to wire bodies, and for creating wire bodies from other entities:

• creating faces to fit wire bodies: see Section 37.2
• blending vertices on wire bodies: see Section 37.3
• offsetting planar wire bodies: see Section 37.4
• changing orientation of edges: see Section 37.5
• splitting wire bodies: see Section 37.6
• creating wire bodies from curves: see Section 37.2
• creating wire bodies from edges: see Section 37.2

[back to top]

37.2 Creating faces to fit wire bodies

Given a closed wire body, it is possible to create a face whose boundary contains the edges of the wire body using PK_EDGE_make_faces_from_wire. This is the reverse operation to piercing the face on a single-faced sheet. The new face created does not have a surface attached, but one may be attached using either PK_FACE_attach_surfs or PK_FACE_attach_surf_fitting.

This function allows faces with holes or bodies with separate profiles to be created. Each loop in a new face is created from a closed loop of edges in the wire body and the function allows you to specify how many faces are created and the sense of each loop with respect to the edges.

The wire body becomes a sheet body if there are no wireframe edges remaining, otherwise it becomes a general body.

[back to top]

37.3 Blending vertices on wire bodies

The blending of vertices in a wire body is done by PK_VERTEX_make_blend, and the principles are exactly the same as for blending vertices of sheet bodies.

See the section on "Blending vertices on sheet bodies" in Chapter 35, "Sheet Modeling", for details of this operation.

[back to top]

37.4 Offsetting planar wire bodies

A planar wire body can be offset in the plane by PK_BODY_offset_planar_wire, producing a new wire body. The body can be offset either inwards or outwards.

Figure 37-1 Various offsets of a wire body (original is the body with no circular edges)

To create the new body, the edge curves are first offset by the specified distance. Then all the new offset curves are processed as follows:

• where pairs of edges still intersect, they are trimmed back to the intersection
• new edge segments are created to fill gaps caused by the splitting of vertices - the application can specify the type of segments to be created:
• round arcs (PK_BODY_owb_gap_fill_round_c), where the original vertex marks the center of the new arc
• tangent extensions (PK_BODY_owb_gap_fill_linear_c)
• curve extensions (PK_BODY_owb_gap_fill_natural_c)

PK_BODY_offset_planar_wire returns information pairing the edges of the new offset wire body with their originating edges or vertices (in the case of new edge segments), using the standard data structure PK_TOPOL_track_r_t.

The geometry of the new edges are only of the same type as the original edges if they were originally lines or circular edges; otherwise they are generated approximately. A tolerance can be supplied for controlling the approximation. Edges may be split to avoid self-intersecting offset.

In the current implementation of PK_BODY_offset_planar_wire, the number of output wire bodies is always one.

[back to top]

37.5 Edge orientation on wire bodies

The direction of the edges of a wire body can be changed with the following functions:

[back to top]

37.6 Splitting a wire body

PK_VERTEX_remove_edge can be used to split a wire body into two bodies.

The function takes a vertex and an edge to be separated, and adds a new vertex to the end of the edge, introducing a cut into the body. If the body is a wire body, and if it is split into two pieces as a result of being cut at the vertex, a new body is created.

[back to top]

37.7 Creating wire bodies from curves

PK_CURVE_make_wire_body_2 creates a wire body from an array of curves. The wire body that is created can be open or closed, and may be disjoint.

PK_CURVE_make_wire_body_2 receives and returns the following arguments:

If any of the supplied curves contain discontinuities, a new edge is created for each continuous section of the curve. Curves are never joined together to form a single edge.

[back to top]

37.7.1 Mapping edges onto originating curves

The edge_index array returns information about which curves in the received curves array were used to create each edge in the resulting body. This is illustrated in Figure 37-2.

Figure 37-2 Mapping supplied curves to returned edges

In Figure 37-2, a wire body containing 4 edges has been created from an array of 2 curves, one of which contains 2 discontinuities. The value of edge_index for this wire body is [0, 1, 1, 1].

Returning this information is controlled using want_index . See Section 37.7.2.

[back to top]

37.7.2 Specifying options

You can set a number of options using the associated PK_CURVE_make_wire_body_o_t options structure, as follows:

[back to top]

37.8 Creating wire bodies from edges

PK_EDGE_make_wire_body creates a wire body from an array of edges. The supplied edges can come from a number of different parts, but they must not intersect or coincide to any degree.

PK_EDGE_make_wire_body receives and returns the following arguments:

PK_EDGE_make_wire_body can return a disjoint wire body if required, and can create a non-manifold body if general topology is enabled in Parasolid.

For information on how to enable the creation of general topology, see Section 7.3, "Creating general bodies".

[back to top]

37.8.1 Specifying options

You can set a number of options using the associated PK_EDGE_make_wire_body_o_t options structure, as follows:

[back to top]