Cubit 15.8 User Documentation
Sculpt options for specifying how the mesh will be smoothed following mesh generation.
Sculpt includes a tiered approach to smoothing to improve element quality. It starts by applying smoothing to all nodes in the mesh and progressively restricts the smoothing operations to only those nodes that fall below a user-defined scaled Jacobian threshold. Default numbers of iterations and thresholds for each smoothing phase have been tuned for general use, however it may be worthwhile to adjust these parameters. The three smoothing phases include:
Smoothing -smo --smoothing --smooth -S <arg> Smoothing method --csmooth -CS <arg> Curve smoothing method --laplacian_iters -LI <arg> Number of Laplacian smoothing iterations --max_opt_iters -OI <arg> Max. number of parallel Jacobi opt. iters. --opt_threshold -OT <arg> Stopping criteria for Jacobi opt. smoothing --curve_opt_thresh -COT <arg> Min metric at which curves won't be honored --max_pcol_iters -CI <arg> Max. number of parallel coloring smooth iters. --pcol_threshold -CT <arg> Stopping criteria for parallel color smooth --max_gq_iters -GQI <arg> Max. number of guaranteed quality smooth iters. --gq_threshold -GQT <arg> Guaranteed quality minimum SJ threshold --geo_smooth_max_deviation -GSM <arg> Geo Smoothing Maximum Deviation Sculpt Command Summary
Command: smooth Smoothing method Input file command: smooth <arg> Command line options: -S <arg> Argument Type: integer (0, 1, 2, 3) Input arguments: off (0) default (1) on (1) fixed_bbox (2) no_surface_projections (3) to_geometry (4) to_geom (4) geo_smooth (5) geometry_smoothing (5) geo_smoothing (5)Command Description:
Automatic adjustment of node locations following meshing to improve element quality. Controls the combined Laplacian and optimization smoothing procedures applied to volume and surface nodes (see csmooth for curve smoothing options) Uses the laplacian_iters, max_opt_iters, opt_threshold, max_pcol_iters, pcol_threshold, mqx_gq_iters and gq_threshold arguments to control the sensitivity and aggressiveness of the smoothing operations. In most cases, the default options for these parameters are sufficient, however increasing iterations or threshold values, while potentially causing longer run times, may result in improved mesh quality.
Smoothing will adjust the location of nodes on surfaces, projecting them to an approximated surface representation defined by interface reconstruction from volume fractions. In addition to turning smoothing on and off, the surface projection characteristics can be adjusted using the bbox_fixed and no_surface_projections options.
Command: csmooth Curve smoothing method Input file command: csmooth <arg> Command line options: -CS <arg> Argument Type: integer (0, 1, 2, ...6) Input arguments: off (0) circle (1) hermite (2) average_tangent (3) neighbor_surface_normal (4) vfrac (5) linear (6)Command Description:
The csmooth option controls the smoothing method used on curves. In most cases the default should be sufficient, however it may be useful to experiment with different options. The default curve smoothing option is vfrac (5). The following curve smoothing options are available:
Command: laplacian_iters Number of Laplacian smoothing iterations Input file command: laplacian_iters <arg> Command line options: -LI <arg> Argument Type: integer >= 0Command Description:
Number of Laplacian smoothing iterations performed when Hybrid smoothing option is used. Default value is 2.
Command: max_opt_iters Max. number of parallel Jacobi opt. iters. Input file command: max_opt_iters <arg> Command line options: -OI <arg> Argument Type: integer >= 0Command Description:
Indicates the maximum number of iterations of optimization-based smoothing to perform. May complete sooner if no further improvement can be made. Default is 5
Command: opt_threshold Stopping criteria for Jacobi opt. smoothing Input file command: opt_threshold <arg> Command line options: -OT <arg> Argument Type: floating point value (-1.0 -> 1.0)Command Description:
Indicates the value for scaled Jacobian where Optimization smoothing will be performed. Elements with scaled Jacobian less than opt_threshold and their neighbors will be smoothed. Default value is 0.6
Command: curve_opt_thresh Min metric at which curves won't be honored Input file command: curve_opt_thresh <arg> Command line options: -COT <arg> Argument Type: floating point value (-1.0 -> 1.0)Command Description:
Indicates the value for scaled Jacobian where if a node that falls on a curve has neighboring quads less than this value, then the smoothing will no longer honor the curve definition. Instead the optimization smoother will attempt to place the node to optimize the neighboring mesh quality, without regard for its placement on its owning curve.
Normally this value should be set close to zero to avoid too many nodes from floating off of their owning curves, however, if mesh quality is constrained by curve geometry, setting this value higher can help to avoid bad or poor quality elements. Default for this value is 0.1.
Command: max_pcol_iters Max. number of parallel coloring smooth iters. Input file command: max_pcol_iters <arg> Command line options: -CI <arg> Argument Type: integer >= 0Command Description:
Maximum number of spot smoothing (also known as parallel coloring) iterations to perform. May complete sooner if no further improvement can be made. Default is 100. See also pcol_threshold.
Command: pcol_threshold Stopping criteria for parallel color smooth Input file command: pcol_threshold <arg> Command line options: -CT <arg> Argument Type: floating point value (-1.0 -> 1.0)Command Description:
Indicates scaled Jacobian threshold for spot smoothing (also known as parallel coloring). A parallel coloring algorithm is used to uniquely identify and isolate nodes to be improved using optimization. Default is 0.2.
Command: max_gq_iters Max. number of guaranteed quality smooth iters. Input file command: max_gq_iters <arg> Command line options: -GQI <arg> Argument Type: integer >= 0Command Description:
Maximum number of guaranteed quality smoothing iterations to perform. Guaranteed quality smoothing performs a constrained Laplacian smoothing algorithm to adjust node locations. If the result of a smoothing operation results in adjacent element quality falling below the specified gq_threshold value, then move distance is cut until minimum threshold is achieved or the metric is improved. To achieve parallel consistency, a parallel coloring methodology is employed. The max_gq_iters defines the maximum number of parallel color iterations employed. Default is 0 (off). Note that guaranteed quality can be utilized in conjunction with other smoothing methods (Laplacian, Optimization and Parallel Coloring), however to be effective it is normally used independent from other smoothing. For example, to use guaranteed quality the following is suggested:
laplacian_iters = 0 max_opt_iters = 0 max_pcol_iters = 0 max_gq_iters = 100
Command: gq_threshold Guaranteed quality minimum SJ threshold Input file command: gq_threshold <arg> Command line options: -GQT <arg> Argument Type: floating point value (-1.0 -> 1.0)Command Description:
Indicates scaled Jacobian threshold for guaranteed quality smoothing. Default is 0.2. see also max_gq_iters
Command: geo_smooth_max_deviation Geo Smoothing Maximum Deviation Input file command: geo_smooth_max_deviation <arg> Command line options: -GSM <arg> Argument Type: floating point value (>= 0.0Command Description: Used only in conjunction with the smooth = geo_smooth option. It controls the maximum distance any individual node can deviate from the geometry definition. If a smoothing operation computes a location that will move a node further than the prescribed geo_smooth_max_deviation value from the geometry, the node movement will be artificially limited by this value. If not specificied, no limitations will be placed on node movement due to smoothing operations when the smooth = geo_smooth is used. A value of zero (0) will constrain all nodes at interfaces to lie on the geometry, similar to the smooth = to_geometry option. When using this option, the maximum deviation from the geometry for any individual node will be reported in the MESH SUMMARY in the Sculpt ouput.