System Attribute Definitions

Contents

• A.1 Introduction
• A.2 System attribute definitions
• A.3 System attribute definitions whose field values define a property
  • A.3.1 Behaviour of empty groups when owning parts are split or merged
  • A.3.2 Colour
  • A.3.3 Colour 2
  • A.3.4 Density attributes
    • A.3.4.1 Density (of a body)
    • A.3.4.2 Edge density attribute
    • A.3.4.3 Face density attribute
    • A.3.4.4 Region density attribute
    • A.3.4.5 Vertex density attribute
  • A.3.5 Hatching
    • A.3.5.1 Hatching attribute
    • A.3.5.2 Parametric hatch
    • A.3.5.3 Parametric hatching (numeric control)
    • A.3.5.4 Planar hatch
    • A.3.5.5 Radial hatch
  • A.3.6 Layer
  • A.3.7 Name
  • A.3.8 Reflectivity
  • A.3.9 Translucency
  • A.3.10 Translucency 2
  • A.3.11 Transparency
  • A.3.12 Unicode name
  • A.3.13 Scale factor
• A.4 System attribute definitions whose presence alone defines a property
  • A.4.1 Behaviour of merged entities in groups
  • A.4.2 Invisibility
  • A.4.3 Non-mergeable edges
  • A.4.4 Region
• A.5 System attribute definitions created and used by Parasolid
  • A.5.1 Faceting attributes
    • A.5.1.1 Incremental faceting
    • A.5.1.2 Facet vertex data

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A.1 Introduction

Parasolid uses attributes internally for various purposes. The attribute definitions for such system attributes are created automatically when Parasolid is started up. These system attribute definitions are provided to allow the user to alter the behaviour of Parasolid when operating on an entity.

Further information about attributes and attribute definitions can be found in See Attributes.

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A.2 System attribute definitions

For each system-defined attribute definition the following information is shown:

• Identifier - the string by which the attribute definition is identified. This begins “SDL/TY” and continues with the name of the attribute.
• To obtain the tag of system attribute definitions, which are created at the start of a Parasolid session, use PK_ATTDEF_find.
• Class - the class of the attribute definition. All the system attribute definitions are of class 1, 3, or 6; attributes of these classes are independent of the size and position of the entity to which they are attached.
• Entity types - the types of entities to which attributes with this definition may be attached. These are represented by the tokens for the types.
• Fields - a description of the data held by an attribute with this definition. The data is held in a series of fields of specified types, represented by the tokens given below, in a specified order. The type of each of the fields is listed, in the order in which it is held by the attribute, and the data item(s) held in each field.
• Set by - how an attribute of this definition and its fields are set and changed.
• Used by - how the attribute is used.

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A.3 System attribute definitions whose field values define a property

The following definitions provide a standard container for certain entity properties. The contents of the attribute fields defines the property and must be set in order for the attribute to be valid and meaningful.

A.3.1 Behaviour of empty groups when owning parts are split or merged

If an empty group has an attribute of this type attached, it indicates the behaviour that should be used if the body that owns the group is split or merged.

PK_GROUP_split_empty_t can take one of the following values:

PK_GROUP_merge_empty_t can take one of the following values:

An empty group with no attribute of this type behaves as though it had an attribute with values PK_GROUP_split_empty_no_c and PK_GROUP_merge_empty_no_c respectively.

A.3.2 Colour

A.3.3 Colour 2

A.3.4 Density attributes

There are density attributes for each of regions, faces, edges and vertices in addition to the system attribute for density of a body.

The region/face/edge/vertex attributes are taken into account when finding the mass, centre of gravity and moment of inertia of a body or of the entity to which the attribute is attached:

• The mass of a region does not include that of any of its faces or edges, and the same applies to faces and edges and their boundaries.
• A void region always has zero mass whatever its density and a solid region inherits its density from the body if it does not have a density of its own.
• The default density for faces, edges and vertices is always zero.

For further information, see Chapter 27, “Mass Properties”.

A.3.4.1 Density (of a body)

• A body without a density attribute is taken to have, by default, a density of 1.0.
• The character field units is not used by Parasolid but it can be set and read by the user.

A.3.4.2 Edge density attribute

• The value of this attribute is treated as a mass per unit length.
• A mass is calculated for an edge only when an edge possesses this attribute. In all other cases the mass of an edge is not defined.
• The character field units is not used by Parasolid but it can be set and read by the user.

A.3.4.3 Face density attribute

• The value of this attribute is treated as a mass per unit area.
• A mass is calculated for a face only when a face possesses this attribute. In all other cases the mass of a face is not defined.
• The character field units is not used by Parasolid but it can be set and read by the user.

A.3.4.4 Region density attribute

• This attribute only makes sense for solid regions; void regions always have a mass of zero.
• A solid region without a density attribute is taken to have, by default, the same density as its owning body.
• The character field units is not used by Parasolid but it can be set and read by the user.

A.3.4.5 Vertex density attribute

• The value of this attribute is treated as a point mass.
• A mass is calculated for a vertex only when a vertex possesses this attribute. In all other cases the mass of a vertex is not defined.
• The character field units is not used by Parasolid but it can be set and read by the user.

A.3.5 Hatching

For further information on the use of hatching attributes see the Section 105.3.18, “Hatching” section in See Rendering Option Settings..

A.3.5.1 Hatching attribute

• For parametric hatching (Hatching type is RROPPA)- the first two real values define the spacing in u and v respectively. The last two values are not used.
• For planar hatching (Hatching type is RROPPH)- the four real values define the hatch orientation as a vector and a spacing between consecutive planes.
• For radial hatching (Hatching type is RROPRH)- the first three real values define the spacing of the hatch lines. The fourth value is not used.

A.3.5.2 Parametric hatch

• For parametric hatching, an attribute with this definition takes precedence over an attribute with the SDL/TYSA_HATCHING definition, if a face has both types of attribute attached.

A.3.5.3 Parametric hatching (numeric control)

• For parametric hatching, an attribute with this definition takes precedence over an attribute with either the SDL/TYSA_HATCHING or the SDL/TYSA_PARAM_HATCH definition if a face has both types of attribute attached.

A.3.5.4 Planar hatch

• For planar hatching, an attribute with this definition takes precedence over an attribute with the SDL/TYSA_HATCHING definition, if a face has both types of attribute attached.
• You can apply more than one planar hatch definition to a face by submitting multiple normal, pitch, and position data in the form of sets of 7 values to the PK_ATTRIB_field_real_c field. This field should, therefore, contain a multiple of 7 real values.'

A.3.5.5 Radial hatch

• For radial hatching, an attribute with this definition takes precedence over an attribute with the SDL/TYSA_HATCHING definition, if a face has both types of attribute attached.

A.3.6 Layer

A.3.7 Name

Entities read into Parasolid from a Romulus 6.0 transmit file have their names held in name attributes. Only entities to which the user has given names are treated in this way.

A.3.8 Reflectivity

A.3.9 Translucency

A.3.10 Translucency 2

A.3.11 Transparency

A body may be rendered transparent if it has an attached transparency attribute with a non-zero transparency coefficient. See Section 105.3.21, “Transparency”, for more information.

A.3.12 Unicode name

This attribute definition provides a Unicode alternative to the ASCII-only Name attribute.

A.3.13 Scale factor

This attribute definition represents the scale factor of a part. See Section 14.9, “Representing models whose parts are of different scales” for more information.

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A.4 System attribute definitions whose presence alone defines a property

The following definitions provide a standard marker for certain entity properties. They have no fields or their fields are unused, but their presence on an entity defines a property.

A.4.1 Behaviour of merged entities in groups

If a group has an attribute of this definition attached, it indicates that alternative behaviour should be used if an entity in the group is merged with an entity not in that group.

A.4.2 Invisibility

A.4.3 Non-mergeable edges

If an edge has an attribute of this definition attached, it indicates that the edge should not be merged in any modelling operations.

A.4.4 Region

• Regional data allows the application to analyse a hidden-line picture for distinct regions in the 2-D view.
• Further information on the use of region attributes can be found in Section 105.3.24, “Regional data”.

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A.5 System attribute definitions created and used by Parasolid

The following definitions are created by Parasolid to store information for use by Parasolid operations.

A.5.1 Faceting attributes

For further information on the use of attributes in faceting, see Section 107.2.16, “Incremental faceting”.

A.5.1.1 Incremental faceting

A.5.1.2 Facet vertex data

For information about how to create or edit incremental faceting attribute definitions for edges and fins, please contact Parasolid Support.

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