Smooth a mesh

How to smooth out regions on meshes.

NoteTo better see the smoothing effect, first shade your mesh by using Diagnostic Shading or WindowDisplay > Hardware Shade. Increasing the mesh Transparency (in the Control Panel) will also help.

Smooth a mesh

1. Choose Mesh > Mesh Cleanup > Mesh Smooth.
2. Select the mesh to smooth.
3. To smooth the entire mesh, go to step 6.
4. Click down with the to place points that will define the region to smooth. At least three points are required to create a region.
   NoteTo modify the position of a point, click and drag it. To add a new point anywhere, click on the line between any two points.
   NoteThe view must be maintained to complete the region. If the view is modified, the polyline region disappears.

   

5. Press the Select button.

   The selected triangles are highlighted in blue.

6. Press the Smooth button repeatedly until the desired amount of smoothness is achieved.

   The mesh updates after each iteration.

   

   NoteTo keep the vertices from moving by more than a certain amount, use the Maximum Permitted option.
7. Use Edit > Undo to undo successive smoothing iterations.

Reduce the complexity of meshes

How to reduce the number of triangles in a mesh while attempting to preserve its shape.

Sometimes, a mesh might contain more triangles than are necessary to accurately represent its shape. The Mesh Reduce tool lets you reduce the number of triangles in a mesh (while attempting to preserve its shape) according to two different methods:

• Based on chordal deviation, given a maximum deviation value.
• Down to a given percentage (fraction) of the original number.

To reduce a mesh based on chordal deviation

1. Choose Mesh > Mesh Cleanup > Mesh Reduce - p.

   The option window opens.

2. In the option window, set Mode to Chordal Deviation.
3. Adjust the Max. Deviation slider to the maximum deviation allowed from the original mesh.
4. Select the mesh to reduce.

   The option window displays the current number of triangles and vertices.

   

5. Press the Reduce button (in the lower right corner of the window).

   Triangles are deleted in the mesh and the option window shows the number of triangles and vertices remaining, as well as the maximum deviation from the original mesh.

   

To reduce a mesh by a given percentage (fraction)

1. Choose Mesh > Mesh Cleanup > Mesh Reduce - p.

   The option window opens.

2. In the option window, set Mode to Fraction.
3. Adjust the Reduction % slider to reflect the percentage of triangles you want to keep in the mesh.
4. Select the mesh to reduce.

   

5. Press the Reduce button.

   Triangles are deleted in the mesh and the option window shows the number of triangles and vertices remainin, as well as the maximum deviation from the original mesh.

6. You can press the Reduce button again to keep reducing the number of triangles in the mesh.

   

Fill holes in a mesh

How to fill up holes in a mesh.

Fill small or simple holes

Use the Mesh Hole Fill tool to fill small holes, or holes located in an area of the mesh which is relatively flat and has no features.

1. Choose Mesh > Mesh Cleanup > Mesh Hole Fill.
2. Select a mesh.

   All the mesh boundaries are highlighted in green.

   

3. Select the boundary of the hole you wish to fill.

   The hole is filled with a mesh that attempts to maintain the curvature properties across all of the triangles that fill the hole (when Quality option is set to Faired).

4. Continue selecting hole boundaries to fill up additional holes. Or press the Fill All button in the option box to fill up all the holes at once.
   NoteUse Edit > Undo to undo any number of hole fillings.

Fill holes that cut across features or abruptly changing curvature

Use the Mesh Patch tool to fill large holes, or holes located in an area of the mesh with features or abrupt changes in curvature.

This tool fills holes in meshes while recognizing the curvature characteristics of the surrounding area. As with the Mesh Hole Fill tool, the boundary of a hole must be a closed region.

To patch a hole while maintaining curvature characteristics

1. Choose Mesh > Mesh patch.
2. Select a mesh.
3. Set the view so that you clearly see both sides of the hole as well as any features running through it.
4. Define two lines on each side of the hole (by putting down four points) that will act as profiles.

   A flowline is created between the two profiles.The profiles and flowline are view based, and will disappear if you change the view. If this happens, you can click Patch View to reset the view

   

5. Modify the shape of the flowline by moving its control points, so that it follows the shape of any feature going through the hole. You can also modify the position of the corner points.
6. Click Build to build a mesh patch.

   A mesh patch is built between the green lines. Shading the mesh will help evaluate the result.

7. Repeat steps 5-6 until satisfied with the result. You may need to hit Patch View if the view was changed.
8. Click Stitch to substitute the patch to the mesh area it covers and stitch it to the surrounding region, forming a single mesh.

Bridge gaps in a mesh

How to build small “bridges” across gaps within a mesh, so that Mesh > Mesh Cleanup > Mesh Hole Fill can be used to fill up the remaining holes.

Build a bridge across a gap in a mesh

1. Choose Mesh > Mesh Cleanup > Mesh Bridge.
2. Select a mesh.

   The mesh boundaries are highlighted in green.

   

   NoteThe tool works only within a single mesh, not between two separate meshes. If you have two meshes, use Mesh > Mesh Partitioning > Mesh merge first to combine them.
3. Click on a boundary to select the first endpoint for the bridge.
4. Click on the opposite boundary to select the second endpoint for the bridge.

   

   Locators indicate the location of the endpoints. The edges that will be used in the bridge are highlighted.

5. Select the locators and move them along the boundaries to fine tune the position of the endpoints.
6. Press Go.

   A “bridge” made up of two triangles is built between the endpoints.

   

7. Use Edit > Undo to undo the bridge and start again if necessary.
   NoteIf you also build a bridge at the other end of the gap, you produce a hole which can then be filled with Mesh > Mesh Cleanup > Mesh Hole Fill.

Repair defects in meshes

How to identify and repair meshes that are degenerate, non-manifold, non-oriented, self-intersecting, or that contain folded edges.

The tests are executed sequentially, and feedback is provided through the option window and prompt line after each repair step. Meshes are repaired by removing the troublesome triangles.

Many tools that act on meshes such as Mesh cut, Mesh offset and Mesh collar will fail on meshes that are non-manifold, non-oriented or self-intersecting. You will be asked to “repair” the meshes first.

A few definitions

degenerate: contains duplicate triangles (i.e. the same three vertices describe two triangles) , or triangles with two or three overlapping vertices.

manifold: no vertex is adjacent to more than two boundary edges, and no edge is shared by more than two triangles.

oriented: the winding of the vertices around the triangles is such that all normals have the same orientation.

self-intersecting: the mesh intersects itself.

folded edges: the angle between any pair of adjacent triangles is less than a given angle.

Repair a mesh

1. Choose Mesh > Mesh Repair - p.

   The Mesh Repair Control window opens.

2. Select a mesh

   Red arrows appear, pointing to problems with the mesh, if any. The prompt line describes what type of problem the arrows represent.

   

   The control window displays mesh information (statistics) and whether or not the mesh satisfies the criteria (passes the tests) defined above. These criteria are examined, and related problems are fixed, one at a time.

   

3. If a test fails, press the Repair button in the lower right corner of the modeling window to start fixing the mesh.
4. Pressing the button more than once may be necessary. Alternatively, press the Repair All button to fix everything in one step.
5. Follow the instructions on the prompt line and keep pressing the Repair button to successively correct the different problems with the mesh.

   Once the process terminates, the mesh boundaries are drawn in red.

   

   See Mesh > Mesh Repair for a detailed description of the Mesh Repair Control window.

   NoteMesh Repair handles Mobius strips by displaying a set of triangles which, when deleted, should remove the embedded mobius strip(s).

Stitch seams between mesh components

How to seal gaps between the boundaries of components in a mesh.

This tool works best to eliminate narrow gaps between boundaries. To fill larger openings, use Mesh > Mesh Cleanup > Mesh Hole Fill.

To stitch components together

1. Choose Mesh > Mesh Stitch.
2. Select a mesh.

   All the boundaries between components are highlighted in green.

   The prompt line indicates how many boundaries were found, and how many are currently selected.

   NoteThe mesh must have at least two boundaries for Mesh Stitch to work on it.

   

3. Select two or more boundaries that form the seam(s) between the pairs of components you want to stitch.

   The boundaries turn yellow and adjacent triangles are highlighted in light blue.

   NoteYou do not need to zoom in to click on the individual boundaries. If you click twice on a seam, Mesh Stitch will select both boundaries.

   

4. Press the Stitch button.

   All gaps along the seams are sealed by moving and combining vertices, and creating new vertices if needed.

   

Reverse the normals on a mesh or mesh component

How to reverse the direction of the normals on mesh components, or on the whole mesh.

Some tools such as Mesh > Mesh Offset, require that all components of a mesh have their normals pointing in the same direction.

To show mismatched normal directions

1. Click the Multi Color icon.
2. Click the small arrowhead to open the options section.
3. Turn on the new Show Orientation option.

   

   If mesh components facing in the same direction (either toward or away from the camera) are shaded in both blue and yellow, your model exhibits mismatched normal directions.

To reverse the direction of normals on a component

1. Choose Mesh > Reverse Mesh Orientation.

   All meshes are shaded in blue and/or yellow. Blue indicates components that have a normal pointing toward the camera, and yellow, away from the camera.

   

2. Select the component that you wish to reverse.
3. Press the Reverse Component button.

   The direction of the normals is reversed on the component. The shading color changes.

   

4. Press Reverse Component again to undo the operation, or select another component to reverse normals on.

   To reverse the normal direction on the whole mesh, press the Reverse Mesh button.

   NoteWhen reversing a component, we reverse the winding (that is the order) of the vertices to cause the normal to change direction. When reversing the whole mesh, we simply change the value of a flag (boolean value) and no reverse winding is done.