Preparing Meshes

Use Terrain Preparation to verify the quality of meshes and repair detected defects. This preparation is a requirement for many further actions.

This task shows you how to:

Before you begin:
  • Depending on the size of the mesh, Terrain Preparation can be time consuming.
  • Repairing or deleting some defects can result in the creation of other defects (for example, repairing non manifold edges leads to isolated zones, deleting non manifold vertices results in new holes to be filled). Therefore the mesh cleaning process may need several iterations.
  • Possible actions are proposed in the dialog box or in a context toolbar as you navigate. Some actions are documented below for given defects. However, they can be proposed for other defects without specific documentation.

 

See Also
More help on this topic

Start Mesh Preparation

You can specify global parameters for the preparation of meshes, retrieve information, and have a view on the quality of the mesh.

  1. From the Prepare section of the action bar, click Terrain Preparation and select the mesh.
    The top bar of the dialog box lets you drive the preparation of the mesh:

    • Name of the mesh
    • Check, repair, and improvement actions
    • Parameters for the detection and improvement .
    • Information about the mesh .
    • Update status of the mesh
      • Mesh pathologies information is not up-to-date.
        Note: To improve productivity, this status lets you work on the mesh. Information resulting from a specific action is updated, whenever possible. However, if you try to show a pathology that no longer exists, the action is canceled, and the pathology line disappears.
      • Up-to-date information, no pathologies.
      • Up-to-date information, pathologies found.
  2. Press to perform and retrieve the results of the control.

    This panel is displayed as you enter Terrain Preparation.

  3. Press Configure. Select the Mesh Pathologies to check and validate.
    • Global Check and Repair all request apply to the selected pathologies.
    • The Mesh Pathologies list is reset when you exit Mesh Preparation.
  4. Click Check.

    Tip: Verify the update status in the top bar.

    • A check is done for the selected pathologies.
    • Results are displayed in the Mesh Pathologies section.
      Note: The Mesh Pathologies section is active only if pathologies are found.
  5. Repair or delete pathologies as explained below.
  6. Press and specify the global parameters for the detection of problems and improvement of the mesh.
    1. Expand the Detection section to specify the Confusing distance used to repair confused vertices or the Cleft distance to repair button holes.
    2. Expand the Improvement section to determine the Small angle threshold used to correct small angles, and the Long edge threshold used to correct too long edges.
  7. Press to retrieve information on the mesh.

    The data cannot be edited, unless specified otherwise.

    1. Expand each section.
    2. Under Statistics and Display, specify the color of cells, or highlight elements.
    3. Under Graphic Properties, specify the display as required.

Repair, and Improve

Pathologies are listed in sections, with possible actions.

Notes:
  • After a pathology is repaired or deleted, a check is performed on only this pathology, turning the global status in the top bar to "not up-to-date".
  • Whenever possible, the color of the elements is preserved, with the following exceptions.
    • Button holes and self-intersections: The mesh is reset to the default color.
    • Newly created triangles and vertices are created with the default color of the mesh.

  1. Place the pointer over the callout.
    An illustration of the defect appears on the left, except for All defects.
  2. On the right of a type, press
    • to show all locations.
    • to navigate along the defects of that type using the arrows in the player.
    • to repair all defects of a given type.
    • to delete all defects of a given type.
  3. Press on the right of All defects to repair all defects listed under Mesh Pathologies in one shot.

    The repair action runs sequentially on each selected defect type, in a default order.

  4. Clear a defect type to skip it.
  5. Press on the right of Mesh Self-intersections.

    • Self-intersection spots are highlighted in soft color. Their intersection line or point is displayed in red.
    • All self-intersection spots are automatically selected.
    • Self-intersection spots are spots where triangles intersect each other, leading to a self-intersection of the mesh.
    • Self-intersection spots are identified within a cell, not on several.
    • You cannot navigate from one self-intersection spot to another.

    1. Press to repair all local intersections. Local intersections are the most common geometric configurations where there are slight overlaps between neighboring triangles and/or slivers.
    Edges of two neighboring triangles are flipped, degenerated triangles that may appear are then collapsed.
    Notes:
    • The repaired mesh may deviate slightly from the initial one, the deviation remaining very low with regard to the size of the model. If you have any doubt, refine the repaired mesh and verify the deviation with the initial one.
    • Repairing is more time consuming than deleting, but is a good alternative to deleting and then filling the resulting holes.
  6. For Holes and boundaries,
    1. Select a boundary in the 3D area.
      A toolbar is displayed under the pointer.
    2. Use this toolbar to select or deselect the boundary, or zoom on the boundary to perform a filling action.
  7. For Button Holes:
    1. Modify the Cleft distance either globally in the Parameters or locally under Button Holes.
    2. Click Show
      Button holes are highlighted in red.

      All button holes are automatically selected.

    3. Click to repair all defects.
      All button holes are repaired.

      The existing vertex is inserted in the facing edge to create a common edge instead of two free edges.

      Notes:
      • Button holes are identified within a cell, not on several.
      • You cannot navigate from one button hole to another.
      • No selective repair.

Remesh

You can either regenerate a defective mesh or create an external envelop around it.

  1. Expand Remeshing.
  2. To regenerate the mesh, press and enter required parameters.
  3. Alternatively, create an external envelop.

    This approach generates the external envelop of the object, as if wrapped into a very thin and flexible plastic film, no matter what is inside the object. Hole maximum size determines the size of the holes to be filled. The example below shows the result external envelop with a small Hole maximum size (top) then with a larger Hole maximum size.

    Note:
    • Surfacic models without thickness nor interior, such as terrain data, design surfaces for car body, are not candidate for this approach. Meshes need to be closed before generating an external envelop.
    • A solid model with cavities leads to a solid model without cavities.
    • Sharp edges may not be as sharp after the external envelop is generated.

    1. Before generating an external envelop, check holes and boundaries and fill major ones (greater than twice Hole maximum size).
    2. Check the thickness of small areas to preserve and adjust Hole maximum size accordingly.
    3. Set Hole maximum size and press .

Check the Mesh Structure

You can correct structure issues in the mesh.

  1. Expand Mesh Structure.
  2. Press to highlight connected zones.

    Tip: Expand the Connected zones section and use the slider to select the zones (from the smallest to the largest number of triangles).

  3. Press to split connected zones in different cells.
  4. For Orientation
    • Use the color editor to change the color of orientations.
    • In the context toolbar, press or to edit orientations.

Check Holes and Boundaries

You can manage holes and boundaries.

  1. Expand Holes and Boundaries.
  2. Press to hide or show the defective elements.
  3. Press to navigate from one defect to the next using the arrows in the player and apply actions from the context toolbar to the defect.
    • to smooth all the boundaries.
    • to fill holes.
    • to edit the mesh.
    • to switch to ghost mode.
    • to display triangles.
  4. Under Holes and Boundaries, use the slider to filter the selection of holes.

    • When the Selection Filter slider is on the left, the selection is empty. All holes and boundaries are selected when the slider is on the right. Only a percentage is selected when the slider is in an intermediate position.
    • Remaining holes and boundaries are sorted from the shortest perimeter to the longest: Moving the slider from left to right selects from the shortest to the longest.
    • Select a hole boundary, and add or remove it from the current selection. The biggest hole found is considered as exterior. Since you usually do not want to fill the outside of the part, this hole is not selected by default.

  5. Still under Holes and Boundaries, fine-tune parameters to fill all selected holes.
    • Points insertion to fill holes.
    • Step to control the maximum length of edges.
    • Shape to control the shape of the curved filling. The filling is computed on a virtual surface with the curvature coefficient given by the slider, the higher the coefficient, the higher the curvature, from flat to rounded.
    • Accuracy that is the maximum deviation to be respected while smoothing boundaries.

    Note: You can fill individual holes from their context toolbar with the same parameters plus the choice of the type of fill (Automatic Fill, Partial Fill or Bridge Creation).

Edit the Mesh

You can edit the mesh to repair it.

Note: Available edition tools depend on the installation, you might have not access to all edition tools.

  1. In Me > Preferences expand the section of the App.
    1. Under Display Modes, under Mesh clear Free edges and select or clear Triangles as required.
  2. Press Create Triangle and do one of the following.
    • Enter three points (vertices of an existing mesh or not).
    • Two neighboring edges of a mesh (with a vertex in common).
    • An edge of an existing mesh and a point (vertex of an existing mesh or not).

    • The pointer provides a visual help.
    • To select an edge or a vertex, move the pointer from inside to outside the mesh.
    • When several items are found around the pointer, only one is highlighted, priority being given to vertices, then to edges. Zoom in to select the required item.

  3. Press Add point and pick the point to add, existing or not.
  4. Press Move point .

    Available for a single point, not for a set of points.

    • Either pick the 3D area to define the new position of the point.

      If you pick a triangle or an edge and drag without releasing the pointer, the closest vertex is moved to the pick and follows the pointer motion.

      If you pick a triangle or an edge without dragging, the closest vertex is moved to the pick location. You can adjust the coordinates.

    • Or pick a vertex and enter the xyz coordinates of the new position (Absolute is selected).
    • Or pick a vertex, clear the Absolute check box, and enter a signed distance to move the point on each global axis.
  5. Press Remove element .
    1. Select the type of element to remove (on the right).
    2. Pick the element to remove.
  6. Press Collapse element .
    1. Select the type of element to collapse (on the right).
    2. Pick the element to collapse.
    Elements are collapsed as follows:
    • Pick the vertex to collapse.

      It is collapsed as shown below.

    • Pick the edge to collapse.

      It is collapsed as shown below.

    • Pick the triangle to collapse.

      It is collapsed as shown below.

  7. Press Flip edge and pick the edge to flip.

    You cannot flip free edges.

Optimize Triangles

You can optimize triangles from their angle or from the length of their edges.

  1. For Small angles, specify the Min angle value.
  2. For Long edges, specify the Max length value.
  3. Press
    • to show related locations.
    • to repair all defects.
    • to delete all locations.
    • to navigate along the locations of that type using the arrows in the player.
    • to switch to ghost mode (context toolbar).
    • to display triangles (context toolbar).