Table 6.105—DRM_Finite_Element_Mesh

Property

Description

Superclass

·         <DRM Primitive Geometry>

Class

·         <DRM Finite Element Mesh>

Subclass

·         none

Definition

This class describes a tessellation of a surface into mesh faces.  Additional data may be associated with each vertex or mesh face.  The surface is represented by a specialized set of <DRM Data Table>s.

More specifically, a <DRM Finite Element Mesh> instance is comprised of:

a. an ordered list of <DRM Vertex> instance components that associates an index number to each <DRM Vertex> instance;

b. a <DRM Mesh Face Table> instance containing the face elements and optionally, the topology of face elements;

c. optionally, other <DRM Property Table> instances providing additional data.

Data associated with <DRM Vertex> instances shall be provided in a <DRM Property Table> instance with  the tag of the <DRM Classification Data> instance set to MESH_NODE_PROPERTY_SET and having the first <DRM Axis> component of DRM class  <DRM Regular Axis> as follows:

Field

Value

axis_type

{TYPE_INDEX, (MESH_VERTEX}} is
an index into the ordered <DRM Vertex> list, identifying the <DRM Vertex> instance for which data is being provided

axis_value_count

total number of <DRM Vertex> instances

value_unit

UNITLESS

value_scale

UNI

first_value

1

spacing

1

Data associated with mesh faces shall be provided in a <DRM Property Table> instance with the tag of the <DRM Classification Data> instance set to MESH_FACE_PROPERTY_SET and having the first <DRM Axis> component of DRM class  <DRM Regular Axis> as follows:

Field

Value

axis_type

{TYPE_INDEX, {MESH_FACE}} is
the index from the <DRM Mesh Face Table>.

axis_value_count

total number of mesh faces in the table

value_unit

UNITLESS

value_scale

UNI

first_value

1

Spacing

1

Example(s)

·         In support of a rain run-off computational model, a ground surface area is triangulated. At each triangle vertex, the gradient, porosity, flow resistance, water capacity, and rain rate are measured.

This data set is represented in a <DRM Finite Element Mesh> instance by:

d. an ordered list of <DRM Vertex> instances (one for each triangle vertex);

e. a <DRM Mesh Face Table> to define the triangles;

f.  a MESH_FACE_PROPERTY_SET <DRM Property Table> for the gradient data; and

g. a MESH_NODE_PROPERTY_SET <DRM Property Table> for the remaining properties.

An example of such a finite element mesh might be shown as in the following figure:

Inherited field elements

field_name

range

Field_Data_Type

none

 

 

Field elements

field_name

range

Field_Data_Type

none

 

 

Associated to (one-way) (inherited)

·         none

Associated to (one-way)

·         none

Associated by (one-way) (inherited)

·         none

Associated by (one-way)

·         none

Associated with (two-way) (inherited)

·         none

Associated with (two-way)

·         none

Composed of (two-way) (inherited)

·         zero or more {ordered} <DRM Attribute Set Index>s

·         zero or one <DRM Classification Data>

·         zero or more {ordered} <DRM Colour>s

·         zero or more {ordered} <DRM Image Mapping Function>s

·         zero or one <DRM Light Rendering Properties>

·         zero or one <DRM Presentation Domain>

·         zero or more <DRM Property Table>s

·         zero or more <DRM Property Table Reference>s

·         zero or more <DRM Property Value>

·         zero or one <DRM Rendering Priority Level>

·         zero or one <DRM Rendering Properties>

·         zero or more <DRM Tack Point>s

·         zero or one <DRM Union Of Primitive Geometry>

Composed of (two-way)

·         three or more {ordered} <DRM Base Vertex>s1

·         one <DRM Mesh Face Table>2

Composed of (two-way metadata) (inherited)

·         zero or one <DRM Time Constraints Data>

Composed of (two-way metadata)

·         none

Component of (two-way) (inherited)

·         one or more <DRM Union of Primitive Geometry>s

Component of (two-way)

·         none

Constraints

·         Colour mapping restrictions

·         Continuous LOD restrictions

·         Image mapping functions and texture coordinates

·         Nested Primitive_Geometry

·         No attribute conflicts

·         Non-crossing aggregations

·         Non-cyclic aggregations

·         Precedence of Attribute_Set_Index

Notes

1 Since a <DRM Base Vertex> requires a <DRM Location>, this forms an enumerated collection of <DRM Location>.

2 A <DRM Polygon> definition data table.

Class diagram

<DRM Finite Element Mesh>