OSSmooth Parameter File

OSSmooth file parameter statements each have following format:

parameter_name        arg1,arg2,...,argn

input_file

Identifies the files to be interpreted by OSSmooth.

arg1

The file name (without extension) of the OptiStruct .fem, .sh, and/or .grid files to be interpreted by OSSmooth.

output_file

Name of the file to be output by OSSmooth.

arg1

Full name of the file output by OSSmooth.

output_code

Identifies the type of output.

arg1

Output format for iso-surface

• "1" Bulk data trias
• "2" IGES patches
• "3" STL trias [default]
• "4" H3D trias

arg2

Output control for tet-meshing of volume enclosed by the iso-surface.

[Default: no tet-meshing]

• "1" Tetra4 + Tria3 elements
• "2" Tetra10 + Tria6 elements
• "3" Tetra4 elements
• "4" Tetra10 elements

The tet-mesh is written in OptiStruct input format to a file <input_file>_mesh.fem. In this file, the design space of the file <input_file>.fem is replaced with a tet-mesh for immediate reanalysis. Loads, boundary conditions, and non-design elements are carried over from the input file.

units

Defines output units for IGES format. This information gets written to the header of the IGES file and may be recognized by your CAD system.

1 (default)

inch

2

mm

4

foot

10

cm

autobead

Improves the recovered geometry from a topography optimization by applying automatic geometry creation.

arg1

Operation flag [integer]

• "0" autobead off
• "1 (default)" autobead on

arg2

Threshold value for creating autobead.

[real, between 0.0 and 1.0, default = 0.3]

arg3

Bead layer [integer]

• "1 (default)" create 1 layer bead
• "2" create 2 layers bead

isosurface

Generate threshold surface from a topology optimization by applying automatic geometry creation.

arg1

Operation flag [integer]

• "0" isosurface off
• "1 (default)" isosurface on

arg2

Type of surface created [integer]

• "0" isosurface only
• "1" isosurface with Optimization-based smoothing
• "2" Element threshold surface
• "3 (default)" isosurface with Laplacian smoothing

For topology results, smoothing maintains the topology as suggested by OptiStruct, but it can deviate from the given density distribution. If option 1 or 3 is used, check the maximum and average smoothing error output by OSSmooth.

arg3

Density threshold for creating isosurface.

[real, between 0.0 and 1.0, default = 0.3]

opti_smoothing

Optimization-based smoothing [Only used if isosurface C2=1].

arg1

Unit-less surface distance coefficient

[real, default = 0.0]

Defines closeness of the smooth surface from the threshold surface. The effect of this coefficient varies for different input meshes. Higher magnitudes, both positive and negative, give smoother results, but the surface deviates more from the original density distribution. The recommended range is from -50 to 50. When the coefficient is set between 0 and 50, the surface usually tends to smooth and shrink. When the coefficient is set between 0 and -50, the surface usually tends to smooth and expand.

arg2

Smooth isosurface boundary flag [integer]

• "0 (default)" boundary not included in smoothing
• "1" boundary included in smoothing

laplacian_smoothing

Laplacian smoothing [Only used if isosurface C2=3].

arg1

Number of iteration for Laplacian smoothing

[integer > 0, default = 10]

arg2

Feature angle threshold in degrees

[real, default = 30.0]

The feature angle is defined as the angle of normal between two intersected element planes. All corners with a feature angle larger than the threshold will be preserved in the smoothing process.

arg3

Smooth isosurface boundary flag [integer]

• "0" boundary not included in smoothing
• "1 (default)" boundary included in smoothing

remesh

Remesh autobead surface and/or isosurface flag [integer]

0 (default)

remesh off

1

remesh on

Remesh detects 2-layer elements around bead shape and/or boundary of isosurface. Use mixed type remesh if input mesh contains any QUAD elements, otherwise remesh with TRIA elements.

surface_reduction

Reduces the number of surfaces representing the geometry. Can reduce the number of surfaces by up to 80 percent.

arg1

Surface reduction flag [integer]

• "0 (default)" no surface reduction
• "1" do surface reduction

arg2

Feature angle threshold in degrees

[real, default = 10.0]

The feature angle is defined as the angle formed by the surface normal of two adjacent elements. The surface reduction will be performed on any two adjacent elements in which the feature angle between the two elements is smaller than the threshold. The greater the threshold, the more surface reduction will be conducted. The valid range of the threshold is [1.0, 80.0].

pure_surf_smoothing

Surface smoothing only.

arg1

Pure surface smoothing flag [integer]

• "0 (default)"
• "1" Optimization-based smoothing
• "2" Laplacian smoothing

arg2

Number of iteration [Only used if G1=2]

[integer > 0, default = 10]

arg3

Feature angle threshold in degrees [Only used if G1=2]

[real, default = 30.0]

The feature angle is defined as the angle of normal between two intersected element planes. All corners with a feature angle larger than the threshold will be preserved in the smoothing process.

pure_surf_reduction

Surface reduction only.

arg1

Pure surface reduction flag [integer]

• "0 (default)" no surface reduction
• "1" do surface reduction

arg2

Feature angle threshold in degrees

[real, default = 10.0]

The feature angle is defined as the angle formed by the surface normal of two adjacent elements. The surface reduction will be performed on any two adjacent elements in which the feature angle between the two elements is smaller than the threshold. The greater the threshold, the more surface reduction will be conducted. The valid range of the threshold is [1.0, 80.0].