IFC 4.3.x development

8.8.3.28 IfcRectangularPyramid

8.8.3.28.1 Semantic definitions at the entity

The IfcRectangularPyramid is a Construction Solid Geometry (CSG) 3D primitive. It is a solid with a rectangular base and a point called apex as the top. The tapers from the base to the top. The axis from the center of the base to the apex is perpendicular to the base. The inherited Position attribute defines the IfcAxisPlacement3D and provides the location and orientation of the pyramid:

  • SELF\IfcCsgPrimitive3D.Position: The location and orientation of the axis system for the primitive. 
  • SELF\IfcCsgPrimitive3D.Position.Location: The center of the circular area being the bottom face of the cone.
  • SELF\IfcCsgPrimitive3D.Position.Position[3]: The z-axis of the inherited placement coordinate system provides the center axis of the IfcRightCircularCone, and the apex is at the Height value applied to the positive direction of the z-axis. The BottomRadius defines the circular base at the xy-plane of the placement coordinate system.

As shown in Figure 1, the pyramid is positioned within its own placement coordinate system. The origin is the center of the bottom rectangle, that lies in the XY plane. The apex lies on the positive z axis at [0, 0, Height].

"pyramid"

HISTORY  New entity in IFC2x3

Texture use definition

On each triangular side face, textures are aligned facing upright. Textures are stretched or repeated to the extent of the base of each face according to RepeatS. Textures are stretched or repeated towards the top point according to Repeat T, where the top point has coordinates of (0.5,1.0) if RepeatT is False.

On the bottom face, textures are aligned facing front-to-back.

Figure 2 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
Side Normal Origin X Origin Y Origin Z S Axis T Axis
Left -X 0 +YLength 0 -Y (towards top point)
Right +X +Xlength 0 0 +Y (towards top point)
Front -Y 0 0 0 +X (towards top point)
Back +Y +XLength +YLength 0 -X (towards top point)
Bottom -Z +XLength 0 0 -X +Y

Figure 2 — Rectangular pyramid textures

8.8.3.28.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.

> IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
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.



> IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
IfcGeometricRepresentationItem
IfcCsgPrimitive3D
1 Position IfcAxis2Placement3D The placement coordinate system to which the parameters of each individual CSG primitive apply.
Dim INVALID The space dimensionality of this geometric representation item, it is always 3.
IfcRectangularPyramid
2 XLength IfcPositiveLengthMeasure The length of the base measured along the placement X axis. It is provided by the inherited axis placement through _SELF\IfcCsgPrimitive3D.Position.P[1]_.
3 YLength IfcPositiveLengthMeasure The length of the base measured along the placement Y axis. It is provided by the inherited axis placement through _SELF\IfcCsgPrimitive3D.Position.P[2]_.
4 Height IfcPositiveLengthMeasure The height of the apex above the plane of the base, measured in the direction of the placement Z axis, the _SELF\IfcCsgPrimitive3D.Position.P[2]_.

8.8.3.28.2 Entity inheritance

dot_inheritance IfcRectangularPyramid IfcRectangularPyramid IfcCsgPrimitive3D IfcCsgPrimitive3D IfcRectangularPyramid->IfcCsgPrimitive3D IfcCsgPrimitive3D_children 4 more... IfcCsgPrimitive3D_children->IfcCsgPrimitive3D IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcCsgPrimitive3D->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.8.3.28.3 Formal representations

ENTITY IfcRectangularPyramid
 SUBTYPE OF (IfcCsgPrimitive3D);
	XLength : IfcPositiveLengthMeasure;
	YLength : IfcPositiveLengthMeasure;
	Height : IfcPositiveLengthMeasure;
END_ENTITY;