IfcBlock

IfcBlock是一个构造实体几何（CSG）三维基本体。它由三个正交轴上的位置和正定距离来定义。继承的Position属性具有IfcAxisPlacement3D类型，并提供：

①SELFIfcCsgPrimitive3D.Position：基本体的轴系统的位置和方向。

②SELFIfcCsgPrimitive3D。位置。位置：块在位置上有一个顶点，边与放置轴正对齐。

XLength、YLength和ZLength属性定义IfcBlock沿三个轴的大小。

注释定义符合ISO/CD 10303-42:1992

块是实心矩形平行六面体，由位置和放置坐标系定义。块由正长度x、y和z沿放置坐标系的轴指定，并且在放置坐标系的原点处有一个顶点。

注：实体改编自ISO 10303-42中定义的块。

纹理定义

在每个侧面上，纹理都是垂直对齐的。在顶面和底面上，纹理前后对齐。纹理根据重复和重复被拉伸或重复到每个面的范围。

图说明了使用钳制纹理的默认纹理映射（RepeatS=False和repeat=False）。左侧的图像显示了S轴指向右侧而T轴指向上方的纹理。右侧的图像显示应用于几何体的纹理，其中X轴指向右侧，Y轴指向左侧，Z轴指向上方。

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

Block textures

#	Attribute	Type	Cardinality	Description	C
IfcRepresentationItem
	LayerAssignment	IfcPresentationLayerAssignment @AssignedItems	S[0:1]	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.	X
	StyledByItem	IfcStyledItem @Item	S[0:1]	Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.	X
IfcGeometricRepresentationItem
IfcCsgPrimitive3D
1	Position	IfcAxis2Placement3D	[1:1]	The placement coordinate system to which the parameters of each individual CSG primitive apply.	X
	Dim :=3	IfcDimensionCount	[1:1]	The space dimensionality of this geometric representation item, it is always 3.	X
IfcBlock
2	XLength	IfcPositiveLengthMeasure	[1:1]	The size of the block along the placement X axis. It is provided by the inherited axis placement through SELFIfcCsgPrimitive3D.Position.P[1].	X
3	YLength	IfcPositiveLengthMeasure	[1:1]	The size of the block along the placement Y axis. It is provided by the inherited axis placement through SELFIfcCsgPrimitive3D.Position.P[2].	X
4	ZLength	IfcPositiveLengthMeasure	[1:1]	The size of the block along the placement Z axis. It is provided by the inherited axis placement through SELFIfcCsgPrimitive3D.Position.P[3].	X

Examples

块几何可以用构造性实体几何模型来表示，表示为CSG基元。

EXPRESS Specification

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