Creating a Topology

You can apply this scenario to a file, when the failure of the topology transfer occurs (in rare cases) and to improve geometry quality.

It is run after Repairing KO Faces and describes how to:

Create solids from faces
Join the surfaces of a model
Improve the quality of the geometry of the solid obtained by Healing in Generative Shape Design

This task shows you how to generate the model topology if it is not contained in the 3D shape representation corresponding to the original file you have imported:

Create a Topology
Analyze the Topology
Reduce Gaps between Surfaces
Create a Solid

Create a Topology

You can create a topology from the surfaces to repair, for example in Generative Shape Design (Transform section).

Import the file.
Click Join , and select all surfaces to repair in the tree to have them ordered by their numbers in the Join Definition dialog box.
The Join operation allows to repair geometry whereas topological healing allows to close topology.
1. Keep Merging distance = 0.001mm and clear the Check Connexity check box.
  The problem is not yet to check whether the surface is closed or even connex.
2. Click Preview.
  - An error message is displayed, saying that some surfaces cannot be integrated to the join.
  - The solution is to withdraw these surfaces.
  - The rejected surfaces are automatically selected in the list, in the Join Definition dialog box.
3. Click Remove Mode to delete them.
1. Click Apply.
2. Click OK.
The resulting join surface includes all surfaces except those that have been rejected.
Check the rejected surfaces: Usually rejected surfaces have a very sharp corner, for instance, a vertex where edges arrive tangent to each other.
1. Insert a new geometrical set and name it SurfacesToAnalyze (for example).
2. In the No Show space, right-click the rejected surfaces and select the Change Geometrical Set... to move them to the SurfacesToAnalyze geometrical set.
3. Hide the initial geometrical set and unhide SurfacesToAnalyze.
4. Reframe on the first surface to recreate and click Boundary to create its complete boundary.
5. Click Disassemble to disassemble the boundary.
  Details about the curves contained in the surface are displayed in the tree.
6. Click Untrim to untrim the surface to process.
7. Click OK when the description message appears.
  A new element is displayed : SurfaceUntrim.1.
Recreate the face by splitting the relevant surfaces by the corresponding curves. Repeat the same operations with the other rejected surfaces. You may also recreate only some of them and use a transformation for the others.
Double click the join you have created in step 2 to edit it and select the corrected faces to add them to the list (Add Mode).
Click OK.
You can now delete SurfacesToAnalyze.

All the surfaces are now inserted into the join: The topology is complete.

Analyze the Topology

You can perform an analysis based on the free sides of the surface.

Free sides may indicate:

Gaps between elements
Missing elements (not converted or not available in original file)
Overlaps (duplicated elements)
Invalid elements (with unexpected shapes).

Under Visualization, select the Surface boundary check box.
Double click the join surface Join.1 in the geometrical set and change its merging distance parameter to 0.01mm (maximum possible value).
Increasing the merging distance will reduce the number of free sides due to gaps. It is a way to highlight the most important holes.
Click Preview, then OK.
If free sides remain, find the type of free side (gap, missing element, overlap, invalid shape).
1. Reframe on a surface surrounded by a free side. Go to the NoShow space to see the original surfaces.
2. Click Connect Checker in the Review section to measure the distance between the surface (Surface.707) and its neighbors.
  The maximum distance is 0. It means that the free side is not due to gap.
3. Select the surface and send it to the visible space.
4. Check it you see a hole instead.
  There is no hole, it means that this surface was duplicated.
5. You have to delete one of the surfaces. Remove the surface from the join, then delete it.
Repeat these steps with the other surfaces.
Some surfaces may be obviously incorrect, their shapes looking strange. The shaded display is typical of a problem in the definition of the boundaries (missing boundary curves, wrong order).
Move the incorrect surfaces from the join into SurfacesToAnalyze.
Then for each of the faces to rebuild:
1. Create the full boundary of the surface.
2. Disassemble the boundary.
3. Untrim the surface.
4. Check the boundary curves and create the missing ones.
5. Recreate the correct surfaces by Split (in datum mode).
6. Add the recreated surfaces to Join.1.
Some surfaces may have no visible free side, but there might be very small holes impossible to detect visually. Select Join.1 and click Boundary.
If the selected surface is closed, you get an explicit message that means that the surface is closed within 0.1mm.
You may now try to reduce the merging distance to find the minimum value that gives a closed surface:
1. Change the merging distance to 0.01mm and check for free sides.
  The surface is closed within 0.01mm.
2. Check with 0.005mm.
  The surface has visible free sides.
3. Check with 0.008mm.
  The surface is closed within 0.008mm. This distance is a good evaluation of the model accuracy.

Reduce Gaps between Surfaces

At this stage, you can decide that the evaluated accuracy is good enough but you may also create a solid and use the Healing to reduce the gaps between surfaces by actually modifying (deforming) the surfaces.

Click Healing

from the Transform section.

Select Join.1.
Enter the value of the tolerance found in the previous step (Merging distance is 0.008mm in this case).
Click OK.

The surface is now both topologically and geometrically closed.

Create a Solid

You can now create a solid.

Click Close Surface

in the Volume section.

Select Join.1 or Healing.1.
A message confirms the operation.
Click OK.

The solid is created and ready for use. The process is now completed.