IFC 4.3.0.0 (IFC4X3) final

8.8.3.3 IfcBlock

8.8.3.3.1 Semantic definition

The IfcBlock is a Construction Solid Geometry (CSG) 3D primitive. It is defined by a position and a positive distance along the three orthogonal axes. The inherited Position attribute has the IfcAxisPlacement3D type and provides:

  • SELF\IfcCsgPrimitive3D.Position: The location and orientation of the axis system for the primitive.
  • SELF\IfcCsgPrimitive3D.Position.Location: The block has one vertex at location and the edges are aligned with the placement axes in the positive sense.

The XLength, YLength, and ZLength attributes define the size of the IfcBlock along the three axes.

block
Figure 8.8.3.3.A — Block geometry

Figure 8.8.3.3.A illustrates geometric parameters of a block where the block positioned within its own placement coordinate system. The values for XLength, YLength, and ZLength are applied to the positive direction of the X, Y, and Z axis.

Texture definition

On each side face, textures are aligned facing upright. On the top and bottom faces, textures are aligned facing front-to-back. Textures are stretched or repeated to the extent of each face according to RepeatS and RepeatT.

Figure 8.8.3.3.B illustrates default texture mapping with a clamped texture (RepeatS=False and RepeatT=False). The image on the left shows the texture where the S axis points to the right and the T axis points up. The image on the right shows the texture applied to the geometry where the X axis points back to the right, the Y axis points back to the left, and the Z axis points up.

texture
Figure 8.8.3.3.B — Block textures
Side Normal Origin X Origin Y Origin Z S Axis T Axis
Left -X 0 +YLength 0 -Y +Z
Right +X +XLength 0 0 +Y +Z
Front -Y 0 0 0 +X +Z
Back +Y +XLength +YLength 0 -X +Z
Bottom -Z 0 +YLength 0 +X -Y
Top +Z 0 0 +ZLength +X +Y
Table 8.8.3.3.C — Texture parameters

8.8.3.3.2 Entity inheritance

8.8.3.3.3 Attributes

# Attribute Type Description
IfcRepresentationItem (2)
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems

Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.
StyledByItem SET [0:1] OF IfcStyledItem FOR Item

Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.
IfcCsgPrimitive3D (2)
1 Position IfcAxis2Placement3D

The placement coordinate system to which the parameters of each individual CSG primitive apply.
* Dim IfcDimensionCount

This attribute is formally derived. 

3

The space dimensionality of this geometric representation item, it is always 3.
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcBlock (3)
2 XLength IfcPositiveLengthMeasure

The size of the block along the placement X axis. It is provided by the inherited axis placement through SELF\IfcCsgPrimitive3D.Position.P[1].
3 YLength IfcPositiveLengthMeasure

The size of the block along the placement Y axis. It is provided by the inherited axis placement through SELF\IfcCsgPrimitive3D.Position.P[2].
4 ZLength IfcPositiveLengthMeasure

The size of the block along the placement Z axis. It is provided by the inherited axis placement through SELF\IfcCsgPrimitive3D.Position.P[3].
Table 8.8.3.3.D

8.8.3.3.4 Formal representation 

ENTITY IfcBlock
 SUBTYPE OF (IfcCsgPrimitive3D);
	XLength : IfcPositiveLengthMeasure;
	YLength : IfcPositiveLengthMeasure;
	ZLength : IfcPositiveLengthMeasure;
END_ENTITY;

8.8.3.3.5 References