Extensible 3D (X3D)

Part 1: Architecture and base components

32 CAD geometry component

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).

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.

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.

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:

- CADAssembly represents a product assembly composed of subassemblies and parts.
- CADPart is a physical object with a defined shape. It is composed of CADFace nodes which represent the spatial boundary of the object.
- 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.

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:

- Text nodes containing annotations and dimension information.
- Shape nodes representing abstract geometric relations such as tolerance data and features.

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

NOTE Self-intersecting quadrilaterals are ill specified and rendering results are undefined.

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.

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.

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.

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.

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.

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 X3D 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):

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

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 specifies represents a 3D shape
consisting of composed of a collection of
individual planar 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:

- If
*normalPerVertex*is TRUE, the normal at each vertex shall be the average of the normals for all quads that share that vertex. - If
*normalPerVertex*is FALSE, the normal at each vertex shall be perpendicular to the face for that quad.

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.

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 specifies represents a 3D shape consisting of 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.

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.

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 |
||

X3DProductStructureChildNode (abstract) |
n/a | ||

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. |