Extensible 3D (X3D)
Part 1: Architecture and base components

32 CAD geometry component

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cube 32.1 Introduction

32.1.1 Name

The name of this component is "CADGeometry". The CADGeometry component provides X3D support for Computer-Aided Design (CAD) model geometry. This name shall be used when referring to this component in the COMPONENT statement (see 7.2.5.4 Component statement).

32.1.2 Overview

This clause describes the CADGeometry component of this part of ISO/IEC 19775. This includes how 3D geometry is specified and what shapes are available. Table 32.1 provides links to the major topics in this clause.

Table 32.1 — Topics

cube 32.2 Concepts

32.2.1 Overview of geometry

The CADGeometry component consists of two types of nodes: product structure nodes and quad geometry nodes. Together, these node types are used to describe CAD-specific data representations for X3D worlds.

32.2.2 Product structure nodes

Three nodes maintain CAD structural relationships. These nodes define the shape of a tangible object. Additional content may be grouped with these nodes using the CADLayer node. These nodes are, in hierarchy order:

  1. CADAssembly represents a product assembly composed of subassemblies and parts.
  2. CADPart is a physical object with a defined shape. It is composed of CADFace nodes which represent the spatial boundary of the object.
  3. CADFace contains a single Shape node defining one face of CADPart.

This hierarchy structures the file in a way that facilitates reuse of the CAD data in different domains.

32.2.3 CAD layer relationships

The CADLayer node allows CADAssembly and CADPart nodes to be grouped together to model relationship beyond assembly structure. It also allows additional content beyond physical shape to be grouped with CADAssembly and CADPart nodes. This additional content may include:

32.2.4 Quad nodes

Quad nodes represent collections of planar quadrilateral polygons. The IndexedQuadSet node specifies the vertices using indices while the QuadSet node specifies the vertices directly.

32.2.5 Common geometry fields

Several 3D CADGeometry nodes share common fields to describe attributes. These fields that specify the vertex ordering and whether the shape is solid are named ccw and solid respectively. Common 3D geometry fields are described in 11.2.3 Common geometry fields.

cube 32.3 Abstract types

32.3.1 X3DProductStructureChildNode

X3DProductStructureChildNode : X3DChildNode {
  SFNode   [in,out] metadata NULL [X3DMetadataObject]
  SFString [in,out] name     ""
}

The X3DProductStructureChildNode abstract node type marks nodes that are valid product structure children.

cube 32.4 Node reference

32.4.1 CADAssembly

CADAssembly : X3DGroupingNode, X3DProductStructureChildNode {
  MFNode   [in]     addChildren
  MFNode   [in]     removeChildren
  MFNode   [in,out] children       []       [X3DChildNode]
  SFBool   [in,out] bboxDisplay    FALSE
  SFNode   [in,out] metadata       NULL     [X3DMetadataObject]
  SFString [in,out] name           ""
  SFBool   [in,out] visible        TRUE
  SFVec3f  []       bboxCenter     0 0 0    (-∞,∞)
  SFVec3f  []       bboxSize       -1 -1 -1 [0,∞) or −1 −1 −1
}

The CADAssembly node holds a set of assemblies or parts grouped together.

The children field can contain X3DChildNode types.

The name field specifies the name of the CADAssembly.

32.4.2 CADFace

CADFace : X3DProductStructureChildNode, X3DBoundedObject {
  SFNode   [in,out] metadata    NULL     [X3DMetadataObject]
  SFBool   [in,out] bboxDisplay FALSE
  SFString [in,out] name        ""
  SFNode   [in,out] shape       NULL     [Shape|LOD|Transform]
  SFBool   [in,out] visible     TRUE
  SFVec3f  []       bboxCenter  0 0 0    (-∞, ∞)
  SFVec3f  []       bboxSize    -1 -1 -1 [0, ∞) or -1 -1 -1
}

The CADFace node holds the geometry representing a face of a part.

The name field specifies the name of the CADFace.

The shape field contains the Shape node providing the geometry and appearance for the face, or a Transform node relocating its children, or an LOD node containing different detail levels of the shape. If an LOD node is provided, each child of the LOD node shall be a single Shape of varying complexity or another Transform node. If a Transform node is provided, each child of the Transform node shall be a single Shape or another Transform or LOD node. In any case, only zero or one Shape under the CADFace node shall be active at any time.

32.4.3 CADLayer

CADLayer : X3DGroupingNode {
  MFNode   [in]     addChildren
  MFNode   [in]     removeChildren
  MFNode   [in,out] children       []       [X3DChildNode]
  SFBool   [in,out] bboxDisplay    FALSE
  SFNode   [in,out] metadata       NULL     [X3DMetadataObject]
  SFString [in,out] name           ""

  SFBool   [in,out] visible        TRUE
  SFVec3f  []       bboxCenter     0 0 0    (-∞,∞)
  SFVec3f  []       bboxSize       -1 -1 -1 [0,∞) or −1 −1 −1
}

The CADLayer node defines a hierarchy of nodes used for showing layer structure for the CAD model.

The name field describes the content of the layer.

The children field contains all nodes defined for this layer.

32.4.4 CADPart

CADPart : X3DGroupingNode, X3DProductStructureChildNode {
  MFNode     [in]     addChildren
  MFNode     [in]     removeChildren
  SFVec3f    [in,out] center           0 0 0    (-∞,∞)
  MFNode     [in,out] children         []       [CADFace]
  SFBool     [in,out] bboxDisplay      FALSE
  SFNode     [in,out] metadata         NULL     [X3DMetadataObject]
  SFString   [in,out] name             ""
  SFRotation [in,out] rotation         0 0 1 0  [-1,1] or (-∞,∞)
  SFVec3f    [in,out] scale            1 1 1    (0,∞)
  SFRotation [in,out] scaleOrientation 0 0 1 0  [-1,1] or (-∞,∞)
  SFVec3f    [in,out] translation      0 0 0    (-∞,∞)
  SFBool     [in,out] visible          TRUE
  SFVec3f    []       bboxCenter       0 0 0    (-∞,∞)
  SFVec3f    []       bboxSize         -1 -1 -1 [0,∞) or −1 −1 −1
}

The CADPart node is a grouping node that defines a coordinate system for its children that is relative to the coordinate systems of its ancestors. See 4.3.5 Transformation hierarchy and 4.3.6 Standard units and coordinate system for a description of coordinate systems and transformations.

The CADPart node represents the location and faces that constitute a part in the CAD model.

10.2.1 Grouping and children node types provides a description of the children, addChildren, and removeChildren fields.

The bboxCenter and bboxSize fields specify a bounding box that encloses the children of the Part node. This is a hint that may be used for optimization purposes. The results are undefined if the specified bounding box is smaller than the actual bounding box of the children at any time. A default bboxSize value, (-1, -1, -1), implies that the bounding box is not specified and, if needed, shall be calculated by the browser. The bounding box shall be large enough at all times to enclose the union of the group's children's bounding boxes; it shall not include any transformations performed by the group itself ( i.e., the bounding box is defined in the local coordinate system of the children).

The translation, rotation, scale, scaleOrientation and center fields define a geometric 3D transformation consisting of (in order):

  1. a (possibly) non-uniform scale about an arbitrary point;
  2. a rotation about an arbitrary point and axis;
  3. a translation.

The center field specifies a translation offset from the origin of the local coordinate system (0,0,0). The rotation field specifies a rotation of the coordinate system. The scale field specifies a non-uniform scale of the coordinate system. The scale field may have values that are positive, negative (indicating a reflection), or zero. A value of zero indicates that any child geometry shall not be displayed. The scaleOrientation specifies a rotation of the coordinate system before the scale (to specify scales in arbitrary orientations). The scaleOrientation applies only to the scale operation. The translation field specifies a translation to the coordinate system.

Given a 3-dimensional point P and Part node, P is transformed into point P' in its parent's coordinate system by a series of intermediate transformations. In matrix transformation notation, where C ( center), SR ( scaleOrientation), T ( translation), R ( rotation), and S ( scale) are the equivalent transformation matrices,

  P' = T * C * R * SR * S * -SR * -C * P

The following Part node:

CADPart {
  center           C
  rotation         R
  scale            S
  scaleOrientation SR
  translation      T
  children         [...]
}

is equivalent to the nested sequence of:

CADPart {
  translation T
  children CADPart {
    translation C
    children CADPart {
      rotation R
      children CADPart {
        rotation SR
        children CADPart {
          scale S
          children CADPart {
            rotation -SR
            children CADPart {
              translation -C
              children [...]
}}}}}}}
The name field documents the name of this part.

32.4.5 IndexedQuadSet

IndexedQuadSet : X3DComposedGeometryNode {
  MFInt32 [in]     set_index       []   [0,∞)
  MFNode  [in,out] attrib          []   [X3DVertexAttributeNode]
  SFNode  [in,out] color           NULL [X3DColorNode]
  SFNode  [in,out] coord           NULL [X3DCoordinateNode]
  SFNode  [in,out] fogCoord        NULL [FogCoordinate]
  SFNode  [in,out] metadata        NULL [X3DMetadataObject]
  SFNode  [in,out] normal          NULL [X3DNormalNode]
  SFNode  [in,out] texCoord        NULL [X3DTextureCoordinateNode]
  SFBool  []       ccw             TRUE
  SFBool  []       colorPerVertex  TRUE
  SFBool  []       normalPerVertex TRUE
  SFBool  []       solid           TRUE
  MFInt32 []       index           []   [0,∞)
}

The IndexedQuadSet node represents a 3D shape composed of a collection of individual quadrilaterals (quads) as depicted in Figure 32.1. IndexedQuadSet uses the indices in its index field to specify the vertices of each quad from the coord field. Each quad is formed from a set of four vertices of the X3DCoordinateNode node identified by four consecutive indices from the index field If the index field does not contain a multiple of four coordinate values, the remaining vertices shall be ignored.

The IndexedQuadSet node is specified in the local coordinate system and is affected by the transformations of its ancestors. Descriptions of the color, coord, normal, and texCoord fields are provided in the X3DColorNode, X3DCoordinateNode, X3DNormalNode, and X3DTextureCoordinateNode nodes, respectively. If values are provided for the color, normal and texCoord fields, the values are applied in the same manner as the values from the coord field and there shall be at least as many values as are present in the coord field. The value of the colorPerVertex field is ignored and always treated as TRUE. If the normal field is not supplied, normals shall be generated as follows:

The solid field determines whether the IndexedQuadSet is visible when viewed from the inside. 11.2.3 Common geometry fields provides a complete description of the solid field.

32.4.6 QuadSet

QuadSet : X3DComposedGeometryNode {
  MFNode  [in,out] attrib          []   [X3DVertexAttributeNode]
  SFNode  [in,out] color           NULL [X3DColorNode]
  SFNode  [in,out] coord           NULL [X3DCoordinateNode]
  SFNode  [in,out] fogCoord        NULL [FogCoordinate]
  SFNode  [in,out] metadata        NULL [X3DMetadataObject]
  SFNode  [in,out] normal          NULL [X3DNormalNode]
  SFNode  [in,out] texCoord        NULL [X3DTextureCoordinateNode]
  SFBool  []       ccw             TRUE
  SFBool  []       colorPerVertex  TRUE
  SFBool  []       normalPerVertex TRUE
  SFBool  []       solid           TRUE
}

The QuadSet node represents a 3D shape that represents a collection of individual planar quadrilaterals.

The coord field contains an X3DCoordinateNode node that defines the 3D vertices that define the quad. Each quad is formed from a consecutive set of four vertices of the coordinate node. If the coordinate node does not contain a multiple of four coordinate values, the remaining vertices shall be ignored.

Figure 32.1 depicts a QuadSet node with two quads. The ordering of the vertices is also shown.

QuadSet

Figure 32.1 — QuadSet node

The QuadSet node is specified in the local coordinate system and is affected by the transformations of its ancestors. Descriptions of the color, coord, normal, and texCoord fields are provided in the X3DColorNode, X3DCoordinateNode, X3DNormalNode, and X3DTextureCoordinateNode nodes, respectively. If values are provided for the color, normal, and texCoord fields, there shall be at least as many values as are present in the coord field. The value of the colorPerVertex field is ignored and always treated as TRUE. If the normal field is not supplied, the normal shall be generated as perpendicular to the face for either version of normalPerVertex.

The solid field determines whether the QuadSet is visible when viewed from the inside. 11.2.3 Common geometry fields provides a complete description of the solid field.

cube 32.5 Support levels

The CADGeometry component provides two levels of support as specified in Table 32.2. Level 1 provides quad support. Level 2 adds support to describe product structure and layers.

Table 32.2 — CADGeometry component support levels

Level Prerequisites Nodes/Features Support
1 Core 1
Grouping 1
Rendering 1
Shape 1
IndexedQuadSet All fields fully supported.
QuadSet All fields fully supported.
2 Core 1
Grouping 1
Rendering 1
Shape 1
CADAssembly All fields fully supported.
CADFace All fields fully supported.
CADLayer All fields fully supported.
CADPart All fields fully supported.

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