System Attribute Definitions

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Chapters

Contents

• A.1 Introduction
• A.2 System attribute definitions
• A.3 Density attributes
  • A.3.1 Density (of a body)
  • A.3.2 Region density attribute
  • A.3.3 Face density attribute
  • A.3.4 Edge density attribute
  • A.3.5 Vertex density attribute
• A.4 Hatching
  • A.4.1 Hatching attribute
  • A.4.2 Planar hatch
  • A.4.3 Radial hatch
  • A.4.4 Parametric hatch
• A.5 Other attributes
  • A.5.1 Region
  • A.5.2 Color
  • A.5.3 Reflectivity
  • A.5.4 Translucency
  • A.5.5 Name
  • Index

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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 behavior of Parasolid when operating on an entity.

Further information about attributes and attribute definitions can be found in Chapter 47, "Attributes"

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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 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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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.

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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.
• For further information see "Mass properties" in Chapter 38, "Enquiry and Output Functions".

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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.

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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.

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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.

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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.

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Hatching

For further information on the use of hatching attributes see the "Hatching" section in Chapter 53, "Rendering Option Settings".

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Hatching attribute

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

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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.

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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.

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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.

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Other attributes

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Region

• Regional data allows the application to analyze a hidden-line picture for distinct regions in the 2D view.
• Further information on the use of region attributes can be found under "Regional data" in Chapter 53, "Rendering Option Settings".

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Color

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Reflectivity

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Translucency

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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.

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