Extensible 3D (X3D)

Part 1: Architecture and base components

14 Geometry2D component

The name of this component is "Geometry2D". 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 Geometry2D component of this part of ISO/IEC 19775. This includes how two-dimensional geometry is specified and what shapes are available. Table 14.1 provides links to the major topics in this clause.

The geometry2D component consists of only geometry nodes since it uses the shape, geometry property, and appearance nodes defined in the Shape component. The geometry2D nodes may be considered to be planar objects.

The two-dimensional coordinate system in which all 2D nodes are specified is defined to be the z=0 plane of the current 3D coordinate system with x- and y-axes coincident with those of the current 3D coordinate system. The origin of the 2D coordinate system is defined to be the origin of the 3D coordinate system. The unspecified z-component of a 2D coordinate is defined to always have value zero. The position and orientation of 2D nodes are affected by all transformations whether 2D or 3D.

Each face in a 2D node is coplanar with the z=0 plane of the coordinate system in which it is defined. Faces have both a front and a back face. The front face is defined to be that on the positive side of the z=0 plane. Faces are subject to culling as defined elsewhere in this standard for 3D geometry.

When 2D nodes are viewed edge-on, they disappear as they have no depth.

The Shape node is defined in 12 Shape component.

Several geometry nodes contain geometric property nodes such as
Coordinate,
Color,
ColorRGBA, and/or Normal. These nodes are
specified in 11
Rendering component. The
*X3DTextureCoordinate*
nodes specified in 18 Texturing component are also
geometry property nodes.

Shape nodes may specify an Appearance node that describes the appearance properties (material and texture) to be applied to the Shape's geometry. Appearance is described in 12 Shape component

The interaction between the appearance properties and properties specific to geometry nodes is described in 12 Shape component.

Arc2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] SFFloat [] endAngle π/2 [-2π,2π] SFFloat [] radius 1 (0,∞) SFFloat [] startAngle 0 [-2π,2π] }

The Arc node specifies a linear circular arc whose center is at (0,0) and
whose angles are measured starting at the positive x-axis and sweeping towards
the positive y-axis. The *radius* field specifies the radius of the circle
of which the arc is a portion. The arc extends from the *startAngle*
counterclockwise to the *endAngle*. The values of *startAngle* and
*endAngle* shall be in the range [-2π,
2π] radians (or the equivalent if a
different angle base unit has been specified).
If *startAngle* and *endAngle*
have the same value, a circle is specified.

See Figure 14.1 for a depiction of the Arc node.

ArcClose2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] SFString [] closureType "PIE" ["PIE"|"CHORD"] SFFloat [] endAngle π/2 [-2π,2π] SFFloat [] radius 1 (0,∞) SFBool [] solid FALSE SFFloat [] startAngle 0 [-2π,2π] }

The ArcClose2D node specifies a portion of a circle whose center is at (0,0)
and whose angles are measured starting at the positive x-axis and sweeping towards
the positive y-axis. The end points of the arc specified are connected as defined
by the *closureType* field. The *radius* field specifies the radius
of the circle of which the arc is a portion. The arc extends from the *startAngle*
counterclockwise to the *endAngle*. The value of *radius* shall be
greater than zero. The values of *startAngle* and *endAngle* shall
be in the range [-2π, 2π]
radians (or the equivalent if a different default angle base unit has been
specified). If
*startAngle* and *endAngle* have
the same value, a circle is specified and *closureType* is ignored.
If the absolute difference between startAngle and endAngle is greater than or
equal to 2π, a complete circle is
produced with no chord or radial line(s) drawn from the center.

A closureType of "PIE" connects the end point to the start point by defining two straight line segments first from the end point to the center and then the center to the start point. This forms a pie wedge as shown in Figure 14.2.

A closureType of "CHORD" connects the end point to the start point by defining a straight line segment from the end point to the start point. This forms an arc segment as shown in Figure 14.3.

Textures are applied individually to each face of the ArcClose2D. On the front (+Z) and back (-Z) faces of the ArcClose2D, when viewed from the +Z-axis, the texture is mapped onto each face with the same orientation as if the image were displayed normally in 2D. TextureTransform affects the texture coordinates of the ArcClose2D (see 18.4.9 TextureTransform).

11.2.3 Common geometry fields provides a
complete description of the *solid* field.

Circle2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] SFFloat [] radius 1 (0,∞) }

The Circle2D node specifies a circle centred at (0,0) in the local 2D
coordinate system. The *radius* field specifies the radius of the
Circle2D. The value of *radius* shall be greater than zero.
Figure 14.4 illustrates the Circle2D node with a
dashed linetype applied.

Disk2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] SFFloat [] innerRadius 0 [0,∞) SFFloat [] outerRadius 1 (0,∞) SFBool [] solid FALSE }

The Disk2D node specifies a circular disk which is centred at (0, 0) in the
local coordinate system. The *outerRadius* field specifies the radius of
the outer dimension of the Disk2D. The *innerRadius* field specifies the
inner dimension of the Disk2D. The value of *outerRadius* shall be greater
than zero. The value of *innerRadius* shall be greater than or equal to
zero and less than or equal to *outerRadius*. If *innerRadius* is zero, the Disk2D is completely filled. Otherwise,
the area within the *innerRadius* forms a hole in the Disk2D. If
*innerRadius* is equal to *outerRadius*, a solid circular line shall be drawn
using the current line properties.
Figure 14.5 illustrates the Disk2D node containing a
non-zero *innerRadius*.

Textures are applied individually to each face of the Disk2D. On the front (+Z) and back (-Z) faces of the Disk2D, when viewed from the +Z-axis, the texture is mapped onto each face with the same orientation as if the image were displayed normally in 2D. TextureTransform affects the texture coordinates of Disk2D nodes (see 18.4.9 TextureTransform).

11.2.3 Common geometry fields provides a
complete description of the *solid* field.

Polyline2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] MFVec2f [] lineSegments [] (-∞,∞) }

The Polyline2D node specifies a series of contiguous line segments in the local 2D coordinate
system connecting the specified vertices. The *lineSegments* field
specifies the vertices to be connected. Figure 14.6 illustrates the Polyline2D node.

Polypoint2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] MFVec2f [in,out] point [] (-∞,∞) }

The Polyline2D node specifies a set of vertices in the local 2D coordinate
system at each of which is displayed a point. The *points* field
specifies the vertices to be displayed.
Figure 14.7 illustrates the Polypoint2D node by
depicting the line in Figure 14.6 (with points
augmented for
illustrative purposes).

Rectangle2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] SFVec2f [] size 2 2 (0,∞) SFBool [] solid FALSE }

The Rectangle2D node specifies a rectangle centred at (0, 0) in the current
local 2D coordinate system and aligned with the local coordinate axes. By default,
the box measures 2 units in each dimension, from -1 to +1. The *size* field
specifies the extents of the box along the X-, and Y-axes respectively and each
component value shall be greater than zero.
Figure 14.8 illustrates the Rectangle2D node
with
a FillProperties node defining a hatch
style.

Textures are applied individually to each face of the Rectangle2D. On the front (+Z) and back (-Z) faces of the Rectangle2D, when viewed from the +Z-axis, the texture is mapped onto each face with the same orientation as if the image were displayed normally in 2D. TextureTransform affects the texture coordinates of the Rectangle2D (see 18.4.9 TextureTransform).

11.2.3 Common geometry fields provides a
complete description of the *solid* field.

TriangleSet2D : X3DGeometryNode { SFNode [in,out] metadata NULL [X3DMetadataObject] MFVec2f [in,out] vertices [] (-∞,∞) SFBool [] solid FALSE }

The TriangleSet2D node specifies a set of triangles in the local 2D coordinate
system. The *vertices* field specifies the triangles to be displayed.
The number of vertices provided shall be evenly divisible by three. Excess
vertices shall be ignored.
Figure 14.9 illustrates
the TriangleSet2D node.

11.2.3 Common geometry fields provides a
complete description of the *solid* field.

Textures are applied individually to each face of the TriangleSet2D. On the front (+Z) and back (-Z) faces of the TriangleSet2D, when viewed from the +Z-axis, the texture is mapped onto each face with the same orientation as if the image were displayed normally in 2D. TextureTransform affects the texture coordinates of the TriangleSet2D (see 18.4.9 TextureTransform).

The Geometry2D component provides two levels of support as specified in Table 14.2. Level 1 provides the basic support for two-dimensional geometry with straight sides. Level 2 adds support for two-dimensional geometry with non-straight sides.

Table 14.2 — Geometry2D component support levels

Level | Prerequisites | Nodes/Features | Support |
---|---|---|---|

1 |
Core 1 Grouping 1 Shape 1 Rendering 1 |
||

Polyline2D | All fields fully supported. | ||

Polypoint2D | All fields fully supported. | ||

Rectangle2D | All fields fully supported. | ||

TriangleSet2D | All fields fully supported. | ||

2 |
Core 1 Grouping 1 Shape 1 Rendering 1 |
||

All Level 1 Geometry2D nodes | All fields fully supported. | ||

Arc2D | All fields fully supported. | ||

ArcClose2D | All fields fully supported. | ||

Circle2D | All fields fully supported. | ||

Disk2D | All fields fully supported. |