# 8.9.3.29 IfcCylindricalSurface

## 8.9.3.29.1 Semantic definition

The cylindrical surface is a surface unbounded in the direction of z. Bounded cylindrical surfaces are defined by using a subtype of IfcBoundedSurface with BasisSurface being a cylindrical surface.

The inherited attributes are interpreted as

• SELF\IfcElementarySurface.Position defines the location and orientation of the cylindrical surface.
• SELF\IfcElementarySurface.Position.Location defines a point on the axis of the cylindrical surface.
• SELF\IfcElementarySurface.Position.P[3] defines the direction of the axis of the cylindrical surface.

C = Position.Location
x = Position.P[1]
y = Position.P[2]
z = Position.P[3]

and the surface is parameterized as:

In the above parameterization the length unit for the unit vectors z is equal to that of the radius R. In the placement coordinate system defined above, the surface is represented by the equation S = 0, where

The direction of the normal is away from the axis of the cylinder.

## 8.9.3.29.4 Formal representation

ENTITY IfcCylindricalSurface
SUBTYPE OF (IfcElementarySurface);
END_ENTITY;