Defined in File Ifc4x3_rc1.h
IfcCylindricalSurface: public Ifc4x3_rc1::IfcElementarySurface¶
Definition from ISO/CD 10303-42:1992: A cylindrical surface is a surface at a constant distance (the radius) from a straight line. A cylindrical surface is defined by its radius and its orientation and location. The data is to be interpreted as follows:
C = Position.Location x = Position.P y = Position.P z = Position.P R = Radius
and the surface is parameterized as:
where the parametric range is -∞ < u,v < ∞ . 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 positive direction of the normal to the surface at any point on the surface is given by
, or as unit normal by
The direction of the normal is away from the axis of the cylinder.
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.
NOTE A bounded cylindrical surface can be defined by an IfcRectangularTrimmedSurface with BasisSurface being the cylindrical surface and U1 = 0°, U2 = 360° and V1 = lower bound in z, V2 = upper bound in z (if the plane angle measure is degree). A bounded cylindrical arc surface is provided with |U1 - U2| < 360° (assuming the Usense and Vsense agree to the sense of the basis surface). NOTE A non-rectangular bounded cylindrical surface, e.g. the surface of a round wall underneath a sloped roof, cab be defined by an IfcCurveBoundedSurface with IfcBoundaryCurve’s, being a collection of p-curve segments. A p-curve is curve which lies on the basis of a surface and is defined in the parameter space of that surface.
The inherited attributes are interpreted as
SELF\IfcElementarySurface.Position defines the location and orientation of the cylindrical surface. SELF\IfcElementarySurface.Position.Location definesd a point on the axis of the cylindrical surface. SELF\IfcElementarySurface.Position.P defines the direction of the axis of the cylindrical surface.
NOTE Corresponding ISO 10303 entity: plane. Please refer to ISO/IS 10303-42:1994, p.70 for the final definition of the formal standard.
HISTORY New class in IFC2x4.
The radius of the cylindrical surface.