IfcRightCircularCylinder

Definition from 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.

Definition from IAI: 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.


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].
When a texture is applied to a cylinder, it is applied differently to the sides, top, and bottom. On the sides, the texture wraps counterclockwise (from above) starting at the back of the cylinder. The texture has a vertical seam at the back, intersecting the X=0 plane, from (0, Radius, 0) to (0, Radius, Height). For the top and bottom caps, a circle is cut out of the unit texture squares centred at bottom (0, 0, 0) and top (0, 0, Height) with dimensions 2 × Radius by 2 × Radius. The top texture appears right side up when the top of the cylinder is tilted toward the +Z-axis, and the bottom texture appears right side up when the top of the cylinder is tilted toward the −Z-axis. TextureTransform affects the texture coordinates of the Cylinder node NOTE see the Extensible 3D (X3D) definition for textures, please note, that all extrusions in IFC are into the positve z axis, whereas in X3D there are into the positive y axis, and the IFC cylinder is positioned at the bottom face, whereas in X3D it is positioned centric..

NOTE Corresponding STEP entity: right_circular_cyclinder, the position attribute has been promoted to the immediate supertype IfcCsgPrimitive3D. Please refer to ISO/IS 10303-42:1994, p. 177 for the final definition of the formal standard.

HISTORY New entity in IFC2x Edition 3.

EXPRESS specification:

ENTITY IfcRightCircularCylinder

SUBTYPE OF ( IfcCsgPrimitive3D);

Height : IfcPositiveLengthMeasure;

Radius : IfcPositiveLengthMeasure;

END_ENTITY;

Attribute definitions:

Height :

Radius :

Inheritance graph

ENTITY IfcRightCircularCylinder;

ENTITY IfcRepresentationItem;

INVERSE

LayerAssignments : SET OF IfcPresentationLayerAssignment FOR AssignedItems;

StyledByItem : SET [0:1] OF IfcStyledItem FOR Item;

ENTITY IfcGeometricRepresentationItem;

ENTITY IfcCsgPrimitive3D;

Position : IfcAxis2Placement3D;

DERIVE

Dim : IfcDimensionCount := 3;

ENTITY IfcRightCircularCylinder;

Height : IfcPositiveLengthMeasure;

Radius : IfcPositiveLengthMeasure;

END_ENTITY;