# Surfaces

A surface represents the geometry associated with a physical part. A surface is a two-dimensional geometric entity that may be used in automatic mesh generation.

The color of a surface is determined by the component collector to which it belongs.

A surface is comprised of one or more faces. Each face contains a mathematical surface and edges to trim the surface, if required. When a surface has several faces, all of the faces are maintained as a single surface entity. Operations performed on the surface affect all the faces that comprise the surface. In general, HyperMesh automatically uses the appropriate number of and type of surface faces to represent the geometry.

The perimeter of a surface is defined by edges. There are four types of surface edges.

Surface edges are different from lines and are sometimes handled differently for certain operations.

The connectivity of surface edges constitutes the geometric topology.
Free Edges
A free edge is an edge that is owned by only one surface.
Free edges are colored red by default.
On a clean model consisting of surfaces, free edges appear only along the outer perimeter of the part and around any interior holes. Free edges that appear between two adjacent surfaces indicate the existence of a gap between the two surfaces. The automesher will leave a gap in the mesh wherever there is a gap between two surfaces.
Shared Edges
A shared edge is an edge that is owned, or shared, by two adjacent surfaces.
Shared edges are colored green by default.
When the edge between two surfaces is a shared edge, there is no gap or overlap between the two surfaces - they are geometrically continuous. The automesher always places seed nodes along the length a shared edge and will produce a continuous mesh without any gaps along that edge. The automesher will not construct any individual elements that cross over a shared edge.
Suppressed Edges
A suppressed edge is shared by two surfaces but it is ignored by the automesher.
Suppressed edges are colored blue by default.
Like a shared edge, a suppressed edge indicates geometric continuity between two surfaces but, unlike a shared edge, the automesher will mesh across a suppressed edge as if it were not even there. The automesher does not place seed nodes along the length of a suppressed edge and, consequently, individual elements will span across it. By suppressing undesirable edges you are effectively combining surfaces into larger logical meshable regions.
Non-Manifold Edges
A non-manifold edge is owned by three or more surfaces.
Non-manifold edges are colored yellow by default.
They typically occur at "T" intersections between surfaces or when two or more duplicate surfaces exist. The automesher always places seed nodes along their length and will produce a continuous mesh without any gaps along that edge. The automesher will not construct any individual elements that cross over a T-joint edge. These edges cannot be suppressed.

## Create Surfaces

• square - Creates two-dimensional square surface primitives (Surfaces panel, Planes panel).
• cylinder full - Creates three-dimensional full cylinder surface primitives (Surfaces panel, Cones panel).
• cylinder partial - Creates three-dimensional partial cylinder surface primitives (Surfaces panel, Cones panel).
• cone full - Creates three-dimensional full cone surface primitives (Surfaces panel, Cones panel).
• cone partial - Creates three-dimensional partial cone surface primitives (Surfaces panel, Cones panel).
• sphere center and radius - Creates three-dimensional sphere surface primitives by specifying the center and radius (Surfaces panel, Spheres panel).
• sphere four nodes - Creates three-dimensional sphere surface primitives by specifying four nodes (Surfaces panel, Spheres panel).
• sphere partial - Creates three-dimensional partial sphere surface primitives (Surfaces panel, Spheres panel).
• torus center and radius - Creates three-dimensional torus surface primitives by specifying the center, normal direction, minor radius and major radius (Surfaces panel, Torus panel).
• torus three nodes - Creates three-dimensional torus surface primitives by specifying three nodes (Surfaces panel, Torus panel).
• torus partial - Creates three-dimensional partial torus surface primitives (Surfaces panel, Torus panel).
• spin - Creates surfaces by spinning lines or a node list around an axis Surfaces panel, Spin panel).
• drag along vector- Creates surfaces by dragging lines or a node list along a vector (Surfaces panel, Drag panel).
• drag along line - Creates surfaces by dragging lines or a node list along a line (Surfaces panel, Line Drag panel).
• drag along normal - Creates surfaces by dragging lines along their normal (Surfaces panel).
• ribs - Creates and modifies simple ribs between two surfaces (Ribs panel).
• ruled - Creates surfaces by interpolating linearly between lines or nodes (Surfaces panel, Ruled panel).
• spline/filler - Creates surfaces by filling in gaps, such as a hole in an existing surface (Surfaces panel, Spline panel, Quick Edit panel).
• skin - Creates surfaces by skinning lines (Surfaces panel, Skin panel).
• fillet - Creates constant radius fillet surfaces across surface edges (Surfaces panel).
• from FE - Creates surfaces that closely fit a selection of shell elements (Surfaces panel).
• meshlines - A toolkit for creating lines associated to shell elements for advanced selection or surface creation (Surfaces panel).
• auto midsurface - Creates midsurface geometry automatically from multiple surfaces or solids (Midsurface panel).
• surface pair - Creates midsurface geometry from one surface pair (Midsurface panel).
• duplicate - Creates surfaces by duplicating existing surfaces. This is available in many panels when the "duplicate" advanced entity selector is available on a surfaces collector.
• Misc. API commands that do not have an associated panel.
• Additional capabilities are available in solidThinking and solidThinking Inspire.

## Edit Surfaces

• delete - Deletes surfaces (Delete panel, Quick Edit panel).
• trim - Trims surfaces using nodes, lines, surfaces and planes (Surface Edit panel, Quick Edit panel).
• untrim/unsplit - Removes various trim/split lines from surfaces (Surface Edit panel, Edge Edit panel, Quick Edit panel).
• offset - Offsets surfaces along their normal directions while maintaining topological connectivity (Surface Edit panel).
• extend - Extends the edges of surfaces to meet or intersect other surfaces (Surface Edit panel, Midsurface panel).
• shrink - Shrinks surfaces by drawing in all surfaces edges (Surface Edit panel).
• defeature - Removes pinholes, surface fillets, edge fillets and duplicate surfaces (Defeature panel, Edge Edit panel).
• midsurfaces - Modifies and edits extracted midsurfaces (Midsurface panel).
• surface edges - Toggles, suppresses, unsuppresses and equivalences surface edges (Edge Edit panel, Quick Edit panel).
• washer - Trims surfaces using free edge closed loop or shared edge offsets (Quick Edit panel).
• autocleanup - Performs basic automatic geometry cleanup functions in preparation for meshing (Autocleanup panel).
• dimensioning - Modifies dimensions of or between surfaces (Dimensioning panel).
• morphing - Morphs surfaces that have had associated nodes morphed away from them (Morph panel).
• translate - Moves surfaces along a vector direction (Translate panel).
• rotate - Rotates surfaces about a vector axis (Rotate panel).
• scale - Scales the dimensions of surfaces either proportionally or uniformly (Scale panel).
• reflect - Reflects surfaces about a plane to create a mirror image (Reflect panel).
• position - Translates and rotate surfaces into new positions (Position panel).
• permute - Switches the coordinates of surfaces (Permute panel).
• renumber - Renumbers surface edges and surfaces (Renumber panel).
• Misc. API commands that do not have an associated panel.
• Additional capabilities are available in solidThinking and solidThinking Inspire.

## Query Surfaces

• shortest distance - Finds the shortest distance between entities (Shortest Distance dialog).
• interference check - Finds penetrations/intersections between geometries (Geometry Interference Check dialog).
• normal - Reviews the normal direction of surfaces (Normals panel).
• organize - Moves surfaces into different component collectors (Organize panel).
• numbers - Displays the IDs of surface edges and surfaces (Numbers panel).
• count - Counts the total or displayed surfaces (Count panel).
• area - Queries the total area of the selected surfaces (Mass Calc panel).
• dimensioning - Queries dimensions of or between surfaces (Dimensioning panel).
• Misc. API commands that do not have an associated panel.