Creating a Curves Network from a Digitization

You can create a network of curves. The edges of this network are curves on mesh, that form loops based on subareas of the mesh. You can edit or split those loops and add more loops.

You can then use the network of curves as input for Surfaces Network.

This task shows you how to:

Before you begin: You need to be familiar with the creation of curves on meshes. See Creating a Curve on Mesh and About Curve on Mesh for more information.
See Also
About Edition in Digitization to Curve Network

Create the First Loop

You must create a first loop to initialize the network of curves.

  1. From the Wireframe section of the action bar, click Digitization to Curve Network , and select a mesh.
  2. Click Add Loop.
    1. If required, adapt the view to your needs.

      You need to pick points on the mesh. Those points are projected on the mesh to create the edges of the loop. This projection is done along the view direction. You can change this view direction according to your needs as you work.

    2. Pick a first point on the mesh.
      • The Curve on Mesh context toolbar is displayed.
      • The point you have picked is displayed as a dot.
      • The red cross is the possible next pick, that follows the cursor, along with the constraint symbol.
  3. Continue picking points on the mesh:
    1. Pick a second point at the next angle, without clicking OK in the Curve On Mesh context toolbar.
      This point is an internal point of the curve on mesh.
    2. Pick a point at the next angle, but this time, click OK in the Curve On Mesh context toolbar.
      This creates a curve on mesh, that is, an edge of the curves network.
    3. Pick a point at the next angle and validate it.

      You can choose the required continuity for any point from the context toolbar.

    4. Pick a point at the next angle without validating it.
    5. Pick a point at the next angle and validate it.
    6. Pick the first point again and click OK in the Curve On Mesh context toolbar.

      It is highlighted as the closing point of the loop.

    The Curve On Mesh context toolbar disappears and the loop is validated and displayed.
    Note: The points you have picked and validated are displayed as green dots. They are nodes of the curves network. The other points are not displayed.

    When you create a loop, create several chained curves on mesh (4 in our example) instead of a single one, resulting in the following advantages:

    • No need to split the edge again to create nodes.
    • Better quality of the curves, with a better respect of the mesh.

    For a better quality of the curves network, do not hesitate to add split points on the curves with Curve on Mesh.

A Digitization To Curve Network.x feature is created.

Important: If the input mesh and/or the segmentation are modified, the curves are updated (the network is not deleted and created anew). This preserves previous interactive modifications on curves and/or network. However, some adjustments may still be required. Use the different colors of the sub-meshes to help you make those adjustments.

If too many adjustments are required, you can edit the feature and reset all the curves.

Manage Edges

You can edit, split, or remove an edge.

  1. Drag the cursor over an edge.
  2. Click Edit Edge .

    Note: When the cursor is on a node, the dominant portion of an edge is displayed as a dotted line, the other portion as a solid line.

    The Curve On Mesh dialog box appears.
  3. As you drag the cursor along the edge, a dot follows the cursor. It represents the candidate node. Position it as required and click Split Edge .
    A node is added to the edge, which is split in two.
  4. Click Remove Edge .
    The edge is deleted:
    • If the edge was common to two loops, the two loops are merged into one.
    • If the edge belonged to one loop, the loop is deleted too.

Manage Nodes

You can edit or remove a node.

  1. Drag the cursor over a node.
  2. Click Edit Node .
  3. Drag the node to move it to the required position.
  4. Click Remove Node .
    The node is removed.

Manage Loops

You can validate or cancel a loop, or add or remove loops, or split a loop, or display statistics.

  1. Right-click anywhere.
  2. Click OK to validate the loop.
  3. Click Remove Loop .
  4. Select two edges of the loop to remove.
    The loop is removed.
  5. Click Display Statistics to display or hide information.
    1. Select the information you want to display.

Add Loops

You can enrich the network by adding loops, preferably outside existing loops.

  1. Create a first loop as explained in Creating a Curves Network from a Digitization.
  2. Add a second loop.

    Remember to verify the view direction!

    Note: When adding a loop, you can pick a node or an edge as the start point. However you cannot pick another edge to close the loop. You can pick only a node as closing point.

  3. Repeat those steps as many times as required to create the network.
  4. Click Surfaces Network and create a surface with this network and the mesh as inputs.

Split Loops

You can enrich the network by splitting loops. This reverts to adding loops inside an existing one.

  1. Split a loop.
    1. Split edges to create two nodes.
    2. Right-click the loop and select Split Loop .
    3. Click the first node you have created.
    4. Click the second node.
    The initial loop is split in two.
    Note: When splitting a loop, you can pick a node or an edge as the start point. However you cannot pick another edge to close the loop. You can pick only a node as closing point.
  2. Edit the edge you have created. Click OK in the Curve on Mesh dialog box when done.
    You cannot move the last point.
  3. Edit this node to move it to the required position.
  4. Repeat as many times as required to complete the network.
  5. Create a surfaces network as explained above.
    Note: Although the result may look the same, splitting a loop and adding a loop inside an existing one lead to two different results.
    • If you split this loop

      the result is two distinct loops.

    • If you add one loop inside it, the result is two loops, with one laying on top of the other.



      This may lead to unexpected results when creating the surfaces network.

    Be careful if you add a loop inside another one, splitting the existing loop may be a better option!

Include an Existing Curve in a Loop

You can add a loop on an existing curve.

  1. To include this curve into a loop:
    1. Click Add Loop .
    2. Pick a first point, then one extremity of the curve and validate this point in the Curve on Mesh dialog box.
    3. Pick a point (no need to pick the second extremity of the curve).
    The curve is included in the loop.
  2. Complete the loop.

Manage Continuity at Nodes

You can manage various continuities at nodes of chained curves.

The scenario below is an example. The context toolbar changes automatically according to the actual continuities.

  1. Consider the following network.
    1. Place the cursor over the first curve. It is displayed in solid.

    2. Place the cursor on the second curve.
      • The second curve is build on the first one: It can be constrained on the first curve, which is its reference.
      • In such a pair, the curve that can be constrained is displayed in solid, the curve that is the reference is displayed in dots.


    3. Place the cursor on the third curve and inspect the pair made by the second and third curves.
      The third curve is build on the second one. The third one can be constrained on the second one, thus it is displayed in solid, whereas the second one has become a reference and is displayed in dots.

  2. Consider any pair of reference curve and curve to constrain.
    • While the cursor on the curve to constrain is still near the reference curve,
      • The reference curve is clearly displayed in dots.
      • The continuity context toolbar is available. You can switch from a point to a tangent continuity, and vice versa.
    • As the cursor goes to the other extremity, the display of the reference curve vanishes and the continuity context toolbar is no longer available.
      Note: if there is a curve acting as a reference curve at this other extremity, a continuity context toolbar remains available.
  3. Switch to a tangent continuity.
    1. Click Invert Tangent to invert the direction of the tangent.
    2. Click Swap Reference to turn the reference curve into the curve to constrain and the curve to constrain into the reference.
  4. When you have switched to a tangent continuity, at a node where there are more than 2 curves, the context toolbar changes again.
    1. Click Change Reference to pair the curve to constrain with another reference curve.