IFC 4.3.x development

8.8.3.32 IfcRightCircularCylinder

8.8.3.32.1 Semantic definitions at the entity

The IfcRightCircularCylinder is a Construction Solid Geometry (CSG) 3D primitive. It is a solid with a circular base and top. The cylindrical surface between if formed by points at a fixed distance from the axis of the cylinder. The inherited Position attribute defines the IfcAxisPlacement3D and provides:

  • 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 cylinder.
  • SELF\IfcCsgPrimitive3D.Position.Position[3]: The z axis provides the center axis and the height is measured from the origin along the positive direction of the z axis.

Figure 1 illustrates geometric parameters of the cylinder. The cylinder is positioned within its own placement coordiante system. The origin is the center of the bottom circular disk, that lies in the XY plane. The center of the top circular disk is on the positive z axis at [0, 0, Height].

"cylinder"

NOTE  Definition according to ISO/CD 10303-42:1992
A right circular cylinder is a CSG primitive in the form of a solid cylinder of finite height. It is defined by an axis point at the centre of one planar circular face, an axis, a height, and a radius. The faces are perpendicular to the axis and are circular discs with the specified radius. The height is the distance from the first circular face centre in the positive direction of the axis to the second circular face centre.

NOTE  Entity adapted from right_circular_cylinder defined in ISO 10303-42.

HISTORY  New entity in IFC2x3.

Texture use definition

On the circular side, textures are aligned facing upright with origin at the back (+Y direction) revolving counter-clockwise. Textures are stretched or repeated to the extent of the circumference according to RepeatS. Textures are stretched or repeated to the extent of the Height according to RepeatT.

On the top and bottom faces, textures are aligned facing front-to-back, with the center of the circle aligned to the center of the texture.

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
Side +Y 0 +Radius 0 -X +Z
Bottom -Z -Radius +Radius 0 +X -Y
Top +Z -Radius -Radius +Height +X +Y

Figure 2 — Right circular cylinder textures

8.8.3.32.1 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.
IfcRightCircularCylinder
2 Height IfcPositiveLengthMeasure The distance between the planar circular faces of the cylinder.
3 Radius IfcPositiveLengthMeasure The radius of the cylinder.

8.8.3.32.2 Entity inheritance

dot_inheritance IfcRightCircularCylinder IfcRightCircularCylinder IfcCsgPrimitive3D IfcCsgPrimitive3D IfcRightCircularCylinder->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

8.8.3.32.3 Formal representations

ENTITY IfcRightCircularCylinder
 SUBTYPE OF (IfcCsgPrimitive3D);
	Height : IfcPositiveLengthMeasure;
	Radius : IfcPositiveLengthMeasure;
END_ENTITY;