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Reverse Engineering in Solid Edge 2020: Remesh Command

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

We have enhanced Reverse Engineering in Solid Edge 2020 by adding the following functionalities. Included below are links to the Help topics for each of these functionalities.

 

  1. Remesh command
  2. Align command
  3. Repair mesh
  4. Section Sketches command

 

In this article, I’ll cover the Remesh command in detail. Other items will be covered in future articles.

 

Remesh command

 

As the name suggests, Remesh command is used to re-mesh the mesh of the mesh models in Solid Edge. By remeshing, you can increase or decrease the mesh density but still maintaining the shape of the model. Below we will see the applications of Remesh command. This command is based on the remeshing technology from another product from Siemens - Star-CCM+.

 

Applications of Remesh command

 

You may have noticed that when a 3D scan of a model is imported in Solid Edge and you try to do some Reverse Engineering operations on it, the actions are sometimes slow. The reason could be the mesh of imported model is very dense and the number of facets could be in millions. The density of the mesh depends on the scanner and the processing done by the software that comes with scanner. Now this very dense mesh may be needed for capturing the minute details of the model, but it may not be required for reverse engineering the model (e.g. extracting faces or using the model in assembly). So, the mesh density can be decreased to increase the performance of Reverse Engineering commands and Remesh command comes in handy in such cases. You can use this command as mesh simplification tool.

 

1.png

 

On the other side, you may have observed that mesh models created from CAD models have non-uniform mesh (i.e. significantly less mesh on planar faces and dense mesh on curvature faces). Automatic regions command does not recognize the analytic faces on such models. So, the mesh needs to be made uniform for automatic recognition. Remesh command comes in handy here too.

 

2.png

 

How to use the Remesh command

Now that we have seen the applications, we will now see how to use the command and what are the options in the command.

 

Below is how the command bar looks when the command is started, and where you select a mesh body.

 

 

3.png

 

On the command bar, you’ll see the toggle buttons - Curvature Refinement, Retain Sharp Edges, and Retain Boundary. As mentioned earlier, Remesh command can increase or decrease the density if mesh but still retaining the shape of the model. The options help in retaining the shape of the model. See images below to understand the effect of the options.

 

4.png5.png6.png

 

Then there are options to enter the desired size of mesh after remeshing:

 

  • Target Size – This is the size of mesh facets edge that the Remesh command aims for in absence of any mesh refinement. In other words, this will be the size of most of the mesh facet edges after remeshing if the model contains only planar faces.
  • Minimum size - This is the lower limit of the facet edge length for mesh refinement. Mesh refinement happens when Remesh command tries to retain the curvature areas or retain the sharp edges or retain the boundary (as can be seen in the images above). Decreasing this size increases the refinement in such areas.
  • Chordal tolerance – Specifies the maximum chordal deviation for areas with high curvature. Decreasing the value produces a more detailed mesh on a curvature area.

 

            7.png

 

When you select a mesh body, the above values are prepopulated based on some calculations so that user can decide the desired mesh size after remeshing. The value shown in the Target size is the calculated average size of the facet edges. And by default, the Minimum Size and Chordal Tolerance values are 50% and 10% of Target Size. These values could be very small if the mesh is very dense (in case of scanned models) or could be higher if mesh is sparse (in case of CAD models). Increasing the value (from the calculated value) will increase the facet size and will simply the mesh and decreasing the value will decrease the facet size and will make the mesh denser and uniform. Remeshing will take more time if the value of Target Size is very small as compared to the model size.

 

Advanced Options -

Apart from these options there are Advanced Options provided for more control (not used as often):

 

1. Minimum face quality: The Minimum Face Quality property for the surface Remesher is a value that ranges from 0 to 1, with 0 being the worst and 1 being perfect. The quality of a triangle is calculated as the ratio of the triangle face area to the area of an equilateral triangle that would exactly fit inside the circumcircle of the triangle. The circumcircle is the circle which touches all three corner points of the original face. In the diagram below, the Minimum Face Quality is defined as:

 

          8.png

 

The default value is 0.05, and it can be changed. Recommended values are in the range 0.01 to 0.1. Values cannot exceed 0.1.

 

The surface Remesher ensures that all the triangles in the resultant surface mesh have a quality equal to or greater than the specified value. This minimum quality is achieved by allowing the mesher to disregard feature edges, move feature vertices, or avoid projecting vertices if necessary. As a result, the surface Remesher removes or improves faces whose quality is below the specified value.

 

2. Surface Growth Rate: This control determines the rate at which face edge sizes vary from one face to its neighbor. The effect is only seen when there is transition from an area of refinement to the rest of the surface mesh. As an example, the default value of 1.3 means that a face edge can be 1.3 times its neighbor length when growing from a short to a long edge length. The recommended range for Surface Growth Rate is 1.1 to 1.6.

 

3. Sharp Edges Angular Tolerance: The angle tolerance is used to check whether an edge is sharp.

 

4. Proximity Refinement & Compatibility Refinement: Activating Compatibility Refinement option imposes a surface growth rate of 2 to limit the difference in face sizes across a gap. Therefore, if the gap between faces is small, the relative size of faces on either side of the gap is close to one another. This option is useful when using the thin mesher, and improves volume mesh quality, as face sizes on opposing sides are similar without explicitly stating a size.

 

This option is similar to proximity refinement. Proximity refinement specifies a mesh size that is based on the gap size and the number of points inside the gap. Whereas, compatibility refinement ensures that the mesh size on either side of the gap is similar. In some cases, this results in fewer elements and a more efficient use of the surface remesher.

 

For example, consider the surface mesh below. The curvature of the cylindrical pin reduces the mesh size near the pin:

 

9.png

 

Applying compatibility refinement has the following effect on the surface mesh opposite the cylindrical pin:

 

10.png

 

As can be seen above, the surface mesh in the region opposite to the cylindrical pin is refined, as the compatibility refinement makes the mesh size across the gap similar. Note that the surface growth rate also influences the mesh size, so the sizes are not identical. The refinement on the surface mesh in turn affects the volume mesh by creating refined and better quality cells in the gap between the pin and opposing surface.

 

For comparison, the following image shows the surface mesh with only proximity refinement activated.

The mesh size on the opposing surface is independent to the cylindrical pin and the region is only refined due to the gap thickness.

 

11.png

 

Thanks for reading. I’m sure the Remesh tool will be of much help during Reverse Engineering processes.