About Curves Networks

We suggest you follow the workflow below.

• Select the curves and the support mesh.
• Set already selected curves as user-frozen curves and verify frozen curves status.
• Apply:
  • If the creation fails, locate and fix errors.
  • If the creation is successful, verify the completeness of the network.
• Adjust the parameters and options, go back to selection and Apply.
• Analyze the Sharp/Smooth edges and deformations.
• Adjust the parameters and options, go back to selection and Apply.
• Delete wires as required.
• Validate.

On a first step, you have created characteristic curves on the cloud. These curves are often approximate and require some preparation.

The preparation can be:

• Slicing that cuts curves or edges in several pieces, according to a pseudo-intersection.
  Note: A pseudo-intersection is the intersection that would exist if two curves were projected onto the current viewing plane.

  • Pseudo-intersection of two curves in the view direction:
    
    
  • In another view:
    
    
  • In the picture below, the arrows point at the minimum distance between the two curves:
    
    
• Deburring to remove undesirable small curve pieces, based on a Min length criterion.

Then, you can create a network from these cleaned curves according to the following:

• A network is a set of closed and connected contours, named wires.
• A contour is a set of connected edges, necessarily closed but not limited to 3 or 4 sides.
• An edge belongs to one contour (free border edge) or 2 contours (common edge).
• If there are no free border edges, the network is closed.
• A node is the topological encounter point of two or more edges. These edges may belong to different contours.

Once the command has detected the topology (node (black arrows), contours (orange arrow), free edges (green arrows), edges (red arrows).

The curves are adapted to the network internal constraints such as:

• Connection constraints on nodes (all edges ending on a common node must be connected on this point)
  
  (the green arrows points to a G0 continuity, the black arrow to a G1 continuity).
• Tangency constraints between two edges on a node.

The parameters Max distance and Filtering are those used in Curves Slice.

Whenever required, Curves Network adjusts the input curves to close gaps, to force tangent continuity or common tangent plane at some nodes of the network.

A frozen curve (or master curve) needs to stay as it is. The neighboring curves are adapted to match the constraint.

A curve can be frozen by the user, or by the system (for example, the curve is linked to a face or is a fictive edge). Decreasing priorities (Curves with lower priority are adapted to curves with higher priority) are applied to solve blocking situations between several frozen curves:

• Face border
• User frozen curve
• Fictive edge
• Standard curve.

For example, a face border cannot be adapted, nor can a user frozen curve, unless to be connected to a face border.

For situations between curves with the same priority:

• For face border and user frozen curve, the process stops and the user is invited to take action.
• Fictive edges are adapted to get a G1 connectivity.

When creating a datum curves network, this check box helps smoothing the network and facilitates 4-sides patches by merging consecutive curves.

Two curves are merged if:

• No other curves join at the same node.
• G1 continuity angular tolerance is respected.

The maximum deformation between the initial curves and the merged ones is controlled (under 0.001 mm).

In the example below, F1 and C1, F2 and C2

can be merged

whereas in the example below, only F1 and C1

can be merged because C3 joins at the same node.