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Coreform Cubit™ User Manual

Coreform Cubit™ User Manual

With the release of Coreform Cubit 2020.2, the name of the former product, Trelis, is no longer used. When encountered the name "Trelis" is functionally equivalent to "Coreform Cubit" or "Cubit" or "CUBIT".

New In Coreform Cubit: Check out all the latest features in Coreform Cubit .

Introduction: A quick overview of some of the main features and goals of the Coreform Cubit Mesh Generation Toolkit, hardware requirements, and where to go for help.

The Power of Customization: A guide for customizing Coreform Cubit workflows and user interface.

Controlling The Application: A description of the Coreform Cubit user environment, including using the graphical user interface, session control, command line syntax, journal files, graphics, entity picking, saving and restoring, etc.

Geometry Operations: A description of Coreform Cubit’s geometry features including building geometry from scratch, manipulating geometry in Coreform Cubit, importing and exporting geometry formats, etc.

Mesh Generation: A description of Coreform Cubit’s mesh generation capabilities, including how to mesh geometry, meshing and smoothing schemes, setting sizes and intervals, importing a mesh, etc.

U-splines: A description of Coreform Cubit’s implementation of Coreform’s revolutionary U-spline technology.

The Finite Element Model: How to set up the finite element model for analysis, including defining boundary conditions, material properties, exporting the finite element model, etc.

Immersive Topology Environment for Meshing (ITEM): A description of Coreform Cubit’s interactive meshing wizard including how to use the wizard, and a guide to geometry clean-up, setting up the finite element model, mesh generation in ITEM, etc.


Known Issues: A listing of known issues in Coreform Cubit


    1 New In Coreform Cubit

      1.1 Release Notes: Coreform Cubit 2020.2

      1.2 Release Notes: Coreform Cubit 2021.11

    2 Introduction

      2.1 How to Use This Manual

      2.2 Key Features

        2.2.1 Geometry Creation, Modification, and Healing

        2.2.2 Isogeometric analysis

        2.2.3 Non-Manifold Topology

        2.2.4 Geometry Decomposition

        2.2.5 Mesh Generation

        2.2.6 Boundary Conditions

        2.2.7 Element Types

        2.2.8 Graphics Display Capabilities

        2.2.9 Graphical User Interface

        2.2.10 Command Line Interface

      2.3 Cubit Support

      2.4 Hardware Requirements

      2.5 Trademark Notice

    3 Controlling The Application

      3.1 Session Control

        3.1.1 Starting and Exiting a Cubit Session

 Starting the Session in Cubit Command Mode

 Windows File Association

        3.1.2 Execution Command Syntax

        3.1.3 Initialization Files

        3.1.4 Environment Variables

        3.1.5 Environment Commands


        3.1.6 Command Syntax

        3.1.7 Command Line Help

        3.1.8 Saving and Restoring a Cubit Session

      3.2 Graphical User Interface

        3.2.1 Coreform Cubit™ Application Window

        3.2.2 Command Panels

 Command Panel Functionality

        3.2.3 Drop Down Menus

        3.2.4 Options Menu

        3.2.5 Undo Button

        3.2.6 Graphics Window

 Viewing Curve Valence

 Selecting Entities in the GUI

 Key Press Commands for the GUI

 Right Click Commands for the GUI Graphics Window

 View Navigation in the GUI

        3.2.7 Tree View

 Model Tree

 Power Tools

 Geometry Power Tools

 Meshing Tools

 Mesh Quality Tools

        3.2.8 Command Line Workspace

        3.2.9 Journal File Editor

        3.2.10 Property Page

        3.2.11 Toolbars

      3.3 Recording And Playback

        3.3.1 Journal File Creation and Playback

        3.3.2 Controlling Playback of Journal Files

        3.3.3 Automatic Journal File Creation

        3.3.4 Idless Journal Files

      3.4 Graphics Window Control

        3.4.1 Command Line View Navigation: Zoom, Pan and Rotate

        3.4.2 Mouse Based View Navigation: Zoom, Pan and Rotate

        3.4.3 Updating the Display

        3.4.4 Graphics Modes

        3.4.5 Drawing, Locating, and Highlighting Entities

        3.4.6 Graphics Clipping Plane

        3.4.7 Colors

        3.4.8 Drawing Locations, Lines and Polygons

        3.4.9 Entity Labels

        3.4.10 Graphics Camera

        3.4.11 Graphics Window Size and Position

        3.4.12 Hardcopy Output

        3.4.13 Graphics Lighting Model

        3.4.14 Mesh Visualization

        3.4.15 Miscellaneous Graphics Options

        3.4.16 Saving Graphics Views

        3.4.17 Geometry and Mesh Entity Visibility

      3.5 Entity Selection And Filtering

        3.5.1 Command Line Entity Specification

        3.5.2 Extended Command Line Entity Specification

        3.5.3 Selecting Entities with the Mouse

   Specifying the type of entity to select

   Selecting the entities

   The Selection Keyword

   Echoing the ID of the Selection

   Using the Picked Group in Commands

   Creating and Modifying Selections

   Rubberband Selection Control

        3.5.4 Extended Selection Dialog

      3.6 Location, Direction, Plane and Axis Specification

        3.6.2 Specifying a Location

        3.6.3 Specifying a Location on a Curve

        3.6.4 Specifying a Direction

        3.6.5 Specifying an Axis

        3.6.6 Specifying a Plane

        3.6.7 Drawing a Location, Direction, or Axis

      3.7 Listing Information

        3.7.1 List Model Summary

        3.7.2 List Geometry

 List Names Example

 List Surface [range] Ids’ Examples

 Using ’List’ for Querying Connectivity.

        3.7.3 List Mesh

        3.7.4 List Special Entities

        3.7.5 List Cubit Environment

 Sample output

    4 Geometry Operations

      4.1 Cubit Geometry Formats

        4.1.5 ACIS Geometry Kernel

        4.1.6 Mesh-Based Geometry

   Using tolerance on STL files

   Using the stitch option on AVS and facet files

   Using the improve option on facet files.

   Smoothing faceted surfaces.

   Creating a thin offset volume

   Creating volumes from surfaces

      4.2 Geometry Creation

        4.2.1 Bottom-Up Geometry Creation

 Creating Volumes

   Sweep Surface Along Vector

   Sweep Surface About Axis

   Sweep Surface Along Curve

   Sweep Surface Perpendicular

   Sweep Surface to a Volume


   Sheet Extended from Surface

   Sweep Curve About Axis

   Stitch Surfaces Together

   Loft Surfaces Together

   Thicken Surfaces

   Sweeping a Surface to a Plane

   Sweep Surface along a Direction

   Sweep Surface along Helix

   Volume Copy

 Creating Curves


   Parabolic, Circular, Ellipse



   Combine Existing Curves

   Arc Three

   Arc End Vertices and Radius

   Arc Center Vertex

   Arc Center Angle

   From Vertex Onto Curve


   From Mesh Edge

   Close To

   Surface Intersection

   By Projection

   Creating a Helix



 Creating Surfaces

   Bounding Curves

   Bounding Vertices or Nodes


   Extended Surface

   Planar Surface

   Net Surface



   Sweeping of Curves


   Weld Profile

   Creating A Surface From Mesh Entities

   Creating a Circular Surface

   Creating a Parallelogram

   Creating an Ellipse

   Creating a Rectangle

 Creating Vertices

   XYZ location

   On Curve - Fraction

   On Curve - General

   From Vertex

   At Arc

   At Intersection

        4.2.2 Geometric Primitives

 Creating Bricks

 Creating Frustums/Cones

 Creating Pyramids

 Creating Toruses

 Creating Cylinders

 Creating Prisms

 Creating Spheres

      4.3 Geometry Transforms

        4.3.1 Align Command

        4.3.2 Copy Command

        4.3.3 Move Command

        4.3.4 Scale Command

        4.3.5 Rotate Command

        4.3.6 Reflect Command

      4.4 Geometry Booleans

        4.4.1 Intersect

        4.4.2 Subtract

        4.4.3 Unite

      4.5 Geometry Decomposition

        4.5.1 Splitting Geometry

 Split Curve

 Split Periodic Surfaces

 Split Surface

     Logical Rectangle

     Split Orientation

     Corner Specification



     Through Vertex





        4.5.2 Web Cutting

 Web Cutting with an Arbitrary Surface

 Chop Command

 Web Cutting with a Planar or Cylindrical Surface

 Web Cutting by Sweeping Curves or Surfaces

 Web Cutting using a Tool or Sheet Body

 Web Cutting Options

        4.5.3 Section Command

        4.5.4 Separating Surfaces from Bodies

        4.5.5 Separating Multi-Volume Bodies

      4.6 Geometry Cleanup and Defeaturing

        4.6.1 Automatic Geometry Clean-up

 Automatic Forced Sweepability


 Automatic Surface Split


 Automatic Small Curve Removal

 Automatic Small Surface Removal


        4.6.2 Healing

 Analyzing Geometry

 Auto Healing

 Healing Attributes

 Spline Removal

 What if Healing is Unsuccessful?

        4.6.3 Removing Geometric Features

 Removing Surfaces

 Removing Vertices

        4.6.4 Tweaking Geometry

 Tweaking Curves

 Tweak Remove Topology

 Tweaking Surfaces

     Hole Removal Example

     Fillet Removal Example

   Changing the Taper of Surfaces

 Tweaking Vertices

 Tweak Volume Bend


        4.6.5 Debugging Geometry

 Related Commands

        4.6.6 Finding Surface Overlap

   Facet - Absolute/Angle

   Gap - Minimum/Maximum

   Angle - Minimum/Maximum








        4.6.7 Geometry Accuracy

        4.6.8 Regularizing Geometry

        4.6.9 Removing Blunt Tangencies

        4.6.10 Stitching Sheet Bodies

        4.6.11 Trimming and Extending Curves

        4.6.12 Validating Geometry

      4.7 Geometry Imprinting and Merging

        4.7.1 Examining Merged Entities

        4.7.2 Imprinting Geometry

        4.7.3 Merge Tolerance

        4.7.4 Merging Geometry

        4.7.5 Using Geometry Merging to Verify Geometry

        4.7.6 Unmerging

      4.8 Virtual Geometry

        4.8.1 Collapse Geometry

 Collapse Angle



 Collapse Curve

 Collapse Surface

        4.8.2 Composite Geometry

 Composite Curves

 Composite Surfaces

        4.8.3 Partitioned Geometry

 Partitioned Curves

 Partitioned Surfaces

 Partitioned Volumes

 Using Mesh Intersections to Partition Surfaces

 Removing Partitions

        4.8.4 Deleting Virtual Geometry

        4.8.5 Simplify Geometry

      4.9 Geometry Orientation

      4.10 Groups

        4.10.1 Basic Group Operations

        4.10.2 Groups in Graphics

        4.10.3 Group Propagation

        4.10.4 Propagated Groups

        4.10.5 Propagated Hex Groups

        4.10.6 Quality Groups

        4.10.7 Seeded Mesh Groups

      4.11 Geometry Attributes

        4.11.1 Entity IDs

        4.11.2 Entity Names

        4.11.3 Persistent Attributes

 Attribute Behavior

 Attribute Commands

 Attribute Types

 Using Cubit Attributes

      4.12 Entity Measurement

      4.13 Geometry Deletion

      4.14 Exporting Geometry

        4.14.1 Exporting ACIS Files

        4.14.2 Exporting Facet and STL Files

        4.14.3 Exporting IGES Files

        4.14.4 Exporting STEP Files

      4.15 Importing Geometry

        4.15.2 Importing ACIS Files

        4.15.3 Importing Facet Files

        4.15.4 Importing FASTQ Files

        4.15.5 Importing Granite Files

        4.15.6 Importing IGES Files

        4.15.7 Importing STEP Files

    5 Meshing Operations

      5.1 Mesh Generation

      5.2 Meshing the Geometry

      5.3 Interval Assignment

        5.3.1 Interval Assignment

        5.3.2 Additional Interval Constraints

        5.3.3 Automatic Specification of Interval Size

        5.3.4 Explicit Specification of Intervals

        5.3.5 Specification of Intervals Using Approximate Size

        5.3.6 Interval Firmness

        5.3.7 Interval Matching

        5.3.8 Mesh Interval Preview

        5.3.9 Periodic Intervals

        5.3.10 Relative Intervals

        5.3.11 Vertex Sizing and Automatic Curve Biasing

        5.3.12 List Interval

      5.4 Meshing Schemes

        5.4.7 Automatic Scheme Selection

        5.4.8 Conversion





        5.4.9 Copying a Mesh

        5.4.10 Radialmesh

        5.4.11 Parallel Meshing


     Sculpt Process Flow

 Sculpt Adaptive Meshing

 Sculpt Application

 Sculpt Boundary Conditions

 Sculpt Boundary Layers

 Sculpt Command Summary

 Sculpt GUI

 Sculpt Mesh Improvement


 Sculpt Input Data Files

 Sculpt Mesh Type

 Sculpt Output

 Sculpt Process Control

 Sculpt Overlay Grid Specification

 Sculpt Smoothing

 Sculpt Technical Description

 Sculpt Mesh Transformation




        5.4.12 Traditional

 Bias, Dualbias










 Quad Dominant






 Surface Vertex Types










      5.5 Mesh Quality Assessment

        5.5.1 Automatic Mesh Quality Assessment

        5.5.2 Coincident Node Check

        5.5.3 Controlling Mesh Quality

        5.5.4 Metrics for Edge Elements

        5.5.5 Finding Intersecting Mesh

        5.5.6 Metrics for Hexahedral Elements

        5.5.7 Mesh Quality Example Output

        5.5.8 Mesh Quality Command Syntax

        5.5.9 Metrics for Quadrilateral Elements

        5.5.10 Metrics for Tetrahedral Elements

        5.5.11 Mesh Topology Check

        5.5.12 Metrics for Triangular Elements

        5.5.13 Metrics for Wedge Elements

      5.6 Mesh Modification

        5.6.1 Mesh Smoothing

 Adjust Boundary Orthogonal

 Centroid Area Pull

 Condition Number

 Edge Length



 Mean Ratio

 Smart Laplacian



        5.6.2 Align Mesh

        5.6.3 Block Repositioning

        5.6.4 Collapsing Mesh

        5.6.5 Creating and Merging Mesh Elements

        5.6.6 Edge Swapping

        5.6.7 Matching Tetrahedral Meshes

        5.6.8 Mesh Cleanup

        5.6.9 Mesh Coarsening

        5.6.10 Mesh Column Operations

        5.6.11 Mesh Refinement

        5.6.12 Mesh Scaling for Flexible Hex Refinement

        5.6.13 Node and Nodeset Repositioning

        5.6.14 Mesh Pillowing

        5.6.15 Remeshing

        5.6.16 Hexset Command

      5.7 Mesh Validity

      5.8 Adaptivity And Sizing Functions

        5.8.1 Mesh Adaptivity and Sizing Functions

        5.8.2 Bias Sizing Function

        5.8.3 Constant Sizing Function

        5.8.4 Curvature Sizing Function

        5.8.5 Exodus II-based Field Function

        5.8.6 Geometry Adaptive Sizing Function (Skeleton Sizing)

        5.8.7 Interval Sizing Function

        5.8.8 Inverse Sizing Function

        5.8.9 Linear Sizing Function

        5.8.10 Sizing Source Sizing Function

        5.8.11 Geometry Adaptive for TriMesh and TetMesh Schemes

      5.9 Mesh Deletion

      5.10 Free Meshes

      5.11 Skinning a Mesh

      5.12 Mesh Import

        5.12.1 Importing a Mesh

        5.12.2 Importing 2D Exodus Files

        5.12.3 Importing Abaqus Files

        5.12.4 Importing Exodus II Files

        5.12.5 Importing Fluent Files

        5.12.6 Importing I-DEAS Files

        5.12.7 Importing Nastran Files

        5.12.8 Importing Patran Files

        5.12.9 Lite Meshes

    6 U-splines

      6.1 U-splines

      6.2 Basic CAD to U-spline workflow

        6.2.1 Building U-spline surfaces

        6.2.2 Building U-spline volumes

 U-spline volumes require swept input meshes

 Source surfaces must be contiguous in many-to-one swept meshes

 Entities cannot be creased using build crease group

        6.2.3 Commands

 set uspline

 build uspline

 build uspline optimized

 fit uspline

 draw uspline

 draw uspline projection_error

 remove uspline

      6.3 Automatic creasing of U-splines

        6.3.1 Creasing of extraordinary vertices

        6.3.2 Continuity grading near creased vertices

        6.3.3 Maintaining distance between perpendicular continuity transitions

        6.3.4 Global creasing options

        6.3.5 Automatic minimal creasing example on a Cubit mesh

        6.3.6 Automatic full creasing on a Cubit mesh

        6.3.7 Automatic full creasing with user-specified creased edges

        6.3.8 Automatic minimial creasing with user-specified creased edges

        6.3.9 U-spline creasing commands

 build uspline crease group

      6.4 Display U-spline projection error in Cubit

      6.5 Save and load U-splines with Cubit file

        6.5.1 Saving considerations

        6.5.2 History and snapshots

      6.6 Exporting U-splines

        6.6.1 Export formats

        6.6.2 Special options for BEXT U-spline export

 Exporting block-partitioned BEXT U-splines

 Exporting U-splines with LS-DYNA node sets

 Exporting block-partitioned U-splines with node sets

 Specifying node offsets to prevent node ID collision

    7 The Finite Element Model

      7.1 Global Element IDs

      7.2 Exodus

        7.2.1 Element Block Specification

        7.2.2 Exodus II File Specification

        7.2.3 Exodus II Model Title

        7.2.4 Exodus Coordinate Frames

        7.2.5 Defining Materials and Media Types

        7.2.6 Exodus Boundary Conditions

        7.2.7 Nodeset and Sideset Specification

      7.3 Non Exodus

        7.3.1 Cubit Boundary Conditions

        7.3.2 Using CFD Boundary Conditions

        7.3.3 Using Constraints

        7.3.4 Using Contact Surfaces

        7.3.5 Cubit Initial Conditions

        7.3.6 Using Loads

        7.3.7 Miscellaneous Boundary Condition Commands

        7.3.8 Using Restraints

        7.3.9 Boundary Condition Sets

      7.4 Export

        7.4.1 Exporting the Finite Element Model

        7.4.2 Defining PARAMS for NASTRAN

        7.4.3 Instancing Parts with ABAQUS

        7.4.4 Exporting an Exodus II File

        7.4.5 Exporting Fluent Grid Files

        7.4.6 Exporting Sierra Files

        7.4.7 Transforming Mesh Coordinates

    8 Customizing The User Experience

      8.1 The Power of Customization

      8.2 Adding Command Panels to the GUI

      8.3 Workflows and Toolbars

    9 Immersive Topology Environment for Meshing (ITEM)

      9.5 Generating a Mesh in ITEM

      9.6 Clean Up the Geometry

        9.6.1 Bad geometry representation

        9.6.2 Small details in the model

        9.6.3 Building a Sweepable Topology

 Blend Surfaces

 Geometry Decomposition

 Recognizing Nearly Sweepable Regions

 Forced Sweepability

        9.6.4 Resolving Problems with Conformal Assemblies

        9.6.5 Contact Surfaces

        9.6.6 Determining an Appropriate Merge Tolerance

        9.6.7 Determining the Small Feature Size

      9.7 How to Use the ITEM Wizard

      9.8 Defining the Geometric Model

        9.8.1 Geometry Formats

        9.8.2  Creating your own geometry

        9.8.3 Scripting

        9.8.4 CUB Files

        9.8.5 Cubit Files

      9.9 Setting up the Finite Element Model

        9.9.1 Element Shape

        9.9.2 FEA Model Size

      9.10 Validating the Mesh in ITEM

    10 Boundary Layers

    11 Python API

      11.1 Python Interface

      11.2 Importing Cubit into Python

      11.3  CubitInterface Namespace Reference

        11.3.1  op_type Description Entity1 Entity2 Params

      11.4  Entity

        11.4.1  Inheritance diagram for Entity:

      11.5  GeomEntity

        11.5.1  Inheritance diagram for GeomEntity:

      11.6  Body

        11.6.1  Inheritance diagram for Body:

      11.7  Volume

        11.7.1  Inheritance diagram for Volume:

      11.8  Surface

        11.8.1  Inheritance diagram for Surface:

      11.9  Curve

        11.9.1  Inheritance diagram for Curve:

      11.10  Vertex

        11.10.1  Inheritance diagram for Vertex:

      11.11  CubitFailureException

        11.11.1  Inheritance diagram for CubitFailureException:

      11.12  InvalidEntityException

        11.12.1  Inheritance diagram for InvalidEntityException:

      11.13  InvalidInputException

        11.13.1  Inheritance diagram for InvalidInputException:

      11.14  MeshErrorFeedback

      11.15  MeshImport

      11.16  CFD_BC_Entity

      11.17  Dir

      11.18  Loc

    12 Cubit commands quick reference

      12.1 Geometry

      12.2 File import

      12.3 Program

      12.4 Entity parsing

      12.5 Groups

      12.6 Graphics

      12.7 Settings

    13 Coreform Lattice GC

      13.1 Lattice GC command reference

        13.1.1 build uspline lattice

        13.1.2 fold uspline lattice ref geom

        13.1.3 export uspline lattice tessellation

    14 Cubit Workflows

      14.1 Building U-spline lattices

        14.1.1 Basic lattice workflow

        14.1.2 User-defined reference cells

 Creating reference cells in Coreform Cubit

 Building lattice structures with user-defined reference cells

        14.1.3 Creating a surface offset

      14.2 Building U-spline meshes for ANSYS LS-DYNA analyses

        14.2.1 Automotive preprocessing in Coreform Cubit

 Importing CAD model geometry

   Stitching single-surface bodies

   Dealing with non-analytic spline entities in CAD

 Cleanup model geometry (Optional)

 Modify BREP topology for quality meshing (Optional)

 Mesh model geometry

 Create subdomains for *SET_ keywords

 Partitioning for multiple LS-DYNA parts

 Constructing the U-spline

 Exporting U-splines for use in LS-DYNA

   Exporting multiple BEXT files

        14.2.2 Preparing LS-DYNA input

 Creating boundary conditions

 Creating rigid connections

 Creating common node connections

 Creating tied contact

 Including generated files

 Required file inclusion order for multiple BEXT files

        14.2.3 Executing ANSYS LS-DYNA


      14.3 Initial set of ANSYS LS-DYNA keywords that support LS-DYNA BEXT input

        14.3.1 Preliminary comments

        14.3.2 ANSYS LS-DYNA supported keywords

    15 Appendix

      15.1 Alpha Commands

        15.1.1 Automatic Detail Suppression

        15.1.2 Automatic Geometry Decomposition

        15.1.3 Cohesive Elements

        15.1.4 Deleting Mesh Elements

        15.1.5 FeatureSize

        15.1.6 Geometry Tolerant Meshing

        15.1.7 Mesh Cutting

        15.1.8 Mesh Grafting

        15.1.9 Optimize Jacobian

        15.1.10 Randomize

        15.1.11 Refine Mesh Boundary

        15.1.12 Super Sizing Function

        15.1.13 Test Sizing Function

        15.1.14 Transition

        15.1.15 Triangle Mesh Coarsening

        15.1.16 Whisker Weave

      15.2 APREPRO

        15.2.1 APREPRO Additional Functionality

        15.2.2 APREPRO Functions

        15.2.3 APREPRO Journaling

        15.2.4 APREPRO Operators

        15.2.5 APREPRO Predefined Variables

        15.2.6 APREPRO Rules

        15.2.7 APREPRO Syntax

        15.2.8 APREPRO Units

      15.3 File Formats

        15.3.1 The Bézier extraction file format


 ANSYS LS-DYNA keyword

 Geometry file formats

   ASCII format

   Binary format

        15.3.2 The Exodus Bézier extraction file format

 Control point information

 Element information

 Node numbering

 Coefficient vectors


     Bézier mesh with two elements

     Spline mesh with two elements

     Rational spline mesh with four elements

      15.4 New In 16

        15.4.1 Boundary Layer Improvements in Trelis 16.0

        15.4.2 New Features in Trelis

        15.4.3 New Features in Trelis 16.3

        15.4.4 New Features in 16.4

        15.4.5 New Features in 16.5

      15.5 Available Colors

      15.6 Element Numbering

      15.7 FASTQ

      15.8 FullHex vs. NodeHex Representation

      15.9 Navigation XML Files

      15.10 Periodic Space Filling Models (Tile)

      15.11 References

      15.12 Style Sheets in Cubit

    16 Known Issues

    17 Credits

      17.1 Additional Copyright Notices