OSSmooth Parameter File

The OSSmooth parameter file is composed of a number of parameter statements, each of which has the following format:

parameter_name arg1,arg2,...,argn

The parameter_name and arguments can be separated either by spaces or commas. The file is not case sensitive.

Comment lines in the OSSmooth parameter file should start with either ‘#’ or ‘$’.

The following is a list of allowable parameters and their respective arguments:

Parameter	Description
input_file	Identifies the files to be interpreted by OSSmooth.
input_file	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.
output_file	arg1	Full name of the file output by OSSmooth.
output_code	Identifies the type of output.
	Argument	Description
	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.
units	1 – inch [default] 2 – mm 4 – foot 6 – m 10 – cm
autobead	Improves the recovered geometry from a topography optimization by applying automatic geometry creation.
	Argument	Description
	arg1	Operation flag [integer]: 0 – autobead off 1 – autobead on [default]
	arg2	Threshold value for creating autobead. [real, between 0.0 and 1.0, default = 0.3]
	arg3	Bead layer [integer]: 1 – create 1 layer bead [default] 2 – create 2 layers bead
isosurface	Generate threshold surface from a topology optimization by applying automatic geometry creation.
	Argument	Description
	arg1	Operation flag [integer]: 0 – isosurface off 1 – isosurface on [default]
	arg2	Type of surface created [integer]: 0 – isosurface only 1 – isosurface with Optimization-based smoothing 2 – Element threshold surface 3 – isosurface with Laplacian smoothing [default] 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].
	Argument	Description
	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 – boundary not included in smoothing [default] 1 – boundary included in smoothing
laplacian_smoothing	Laplacian smoothing [Only used if isosurface C2=3].
	Argument	Description
	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 – boundary included in smoothing [default]
remesh	Remesh autobead surface and/or isosurface flag [integer]: 0 – remesh off [default] 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%.
	Argument	Description
	arg1	Surface reduction flag [integer]: 0 – no surface reduction [default] 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.
	Argument	Description
	arg1	Pure surface smoothing flag [integer]: 0 – no surface smoothing [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.
	Argument	Description
	arg1	Pure surface reduction flag [integer]: 0 – no surface reduction [default] 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].

OSS Example Input File

Parameter	Description
input_file example	Identifies the root of the input files as example, so OSSmooth will look for the files example.fem, example.grid, and example.sh.
output_file example.stl	The resulting output will be example.stl.
output_code 3	The output will be in stereolithography format.
Autobead 1 0.3 1	Topography results will be interpreted using the autobead feature with a threshold value of 30% creating single depth beads.
Isosurface 1 3 0.3	Topology results will be interpreted by creating an iso-density boundary surface with at a density value of 30% and smooth using laplacian smoothing.
laplacian_smoothing 10 30 1	The Laplacian smoothing will run for 10 iterations, consider a feature angle of 30-degrees and including the boundary in the smoothing.
Remesh 1	The two rows of elements around the recovered geometry will be remeshed in an attempt to smooth the mesh transition.