@Young_Geon_Park
Did you read further down in the text for the STP export, it is defined as a cylindrical surface, see below. If I open this STP in SolidWorks, it detects the surface as cylindrical. This was generated using the cylinder in Rhino’s solid tools tab.
cylinder solid ap242.stp (4.4 KB)
cylinder solid.3dm (57.4 KB)
As far as using subd to define a “pure” cylindrical surface, it is impossible, see response from @dalelear in this thread [WISH] SubD second degree or changing degree of a SubD? - #5 by martinsiegrist
ISO-10303-21;
HEADER;
/* Generated by software containing ST-Developer
- from STEP Tools, Inc. (www.steptools.com)
/
/ OPTION: using custom schema-name function */
FILE_DESCRIPTION(
/* description / (‘’),
/ implementation_level */ ‘2;1’);
FILE_NAME(
/* name / ‘cylinder solid ap242’,
/ time_stamp / ‘2025-07-01T21:39:25-04:00’,
/ author / (‘’),
/ organization / (‘’),
/ preprocessor_version / ‘ST-DEVELOPER v19.2’,
/ originating_system / ‘Rhino 8.20’,
/ authorisation */ ‘’);
FILE_SCHEMA ((‘AP242_MANAGED_MODEL_BASED_3D_ENGINEERING_MIM_LF { 1 0 10303 442 3 1 4 }’));
ENDSEC;
DATA;
#10=SHAPE_REPRESENTATION_RELATIONSHIP(‘’,‘’,#59,#13);
#11=PRESENTATION_LAYER_ASSIGNMENT(‘Default’,‘’,(#12));
#12=MANIFOLD_SOLID_BREP(‘brep_1’,#14);
#13=ADVANCED_BREP_SHAPE_REPRESENTATION(‘brep_rep_0’,(#12,#66),#58);
#14=CLOSED_SHELL(‘’,(#15,#16,#17));
#15=ADVANCED_FACE(‘’,(#18),#40,.T.);
#16=ADVANCED_FACE(‘’,(#19),#38,.T.);
#17=ADVANCED_FACE(‘’,(#20),#39,.T.);
#18=FACE_OUTER_BOUND(‘’,#21,.T.);
#19=FACE_OUTER_BOUND(‘’,#22,.T.);
#20=FACE_OUTER_BOUND(‘’,#23,.T.);
#21=EDGE_LOOP(‘’,(#24,#25,#26,#27));
#22=EDGE_LOOP(‘’,(#28));
#23=EDGE_LOOP(‘’,(#29));
#24=ORIENTED_EDGE(‘’,,,#30,.T.);
#25=ORIENTED_EDGE(‘’,,,#31,.T.);
#26=ORIENTED_EDGE(‘’,,,#32,.F.);
#27=ORIENTED_EDGE(‘’,,,#31,.F.);
#28=ORIENTED_EDGE(‘’,,,#30,.F.);
#29=ORIENTED_EDGE(‘’,,,#32,.T.);
#30=EDGE_CURVE(‘’,#36,#36,#34,.T.);
#31=EDGE_CURVE(‘’,#36,#37,#33,.T.);
#32=EDGE_CURVE(‘’,#37,#37,#35,.T.);
#33=(
BOUNDED_CURVE()
B_SPLINE_CURVE(1,(#85,#86),.UNSPECIFIED.,.F.,.F.)
B_SPLINE_CURVE_WITH_KNOTS((2,2),(0.,60.),.UNSPECIFIED.)
CURVE()
GEOMETRIC_REPRESENTATION_ITEM()
RATIONAL_B_SPLINE_CURVE((1.,1.))
REPRESENTATION_ITEM(‘’)
);
#34=CIRCLE(‘’,#64,50.);
#35=CIRCLE(‘’,#65,50.);
#36=VERTEX_POINT(‘’,#82);
#37=VERTEX_POINT(‘’,#83);
#38=PLANE(‘’,#62);
#39=PLANE(‘’,#63);
#40=CYLINDRICAL_SURFACE(‘’,#61,50.);
#41=SHAPE_DEFINITION_REPRESENTATION(#42,#59);
#42=PRODUCT_DEFINITION_SHAPE(,,#44);
#43=PRODUCT_DEFINITION_CONTEXT(‘3D Mechanical Parts’,#48,‘design’);
#44=PRODUCT_DEFINITION(‘A’,‘First version’,#45,#43);
#45=PRODUCT_DEFINITION_FORMATION_WITH_SPECIFIED_SOURCE(‘A’,
‘First version’,#50,.MADE.);
#46=PRODUCT_RELATED_PRODUCT_CATEGORY(‘tool’,‘tool’,(#50));
#47=APPLICATION_PROTOCOL_DEFINITION(‘Draft International Standard’,
‘automotive_design’,1999,#48);
#48=APPLICATION_CONTEXT(
‘data for automotive mechanical design processes’);
#49=PRODUCT_CONTEXT(‘3D Mechanical Parts’,#48,‘mechanical’);
#50=PRODUCT(‘Document’,‘Document’,‘’,(#49));
#51=(
LENGTH_UNIT()
NAMED_UNIT()
SI_UNIT(.MILLI.,.METRE.)
);
#52=(
NAMED_UNIT()
PLANE_ANGLE_UNIT()
SI_UNIT(,.RADIAN.)
);
#53=DIMENSIONAL_EXPONENTS(0.,0.,0.,0.,0.,0.,0.);
#54=PLANE_ANGLE_MEASURE_WITH_UNIT(PLANE_ANGLE_MEASURE(0.01745329252),#52);
#55=(
CONVERSION_BASED_UNIT('DEGREES',#54)
NAMED_UNIT(#53)
PLANE_ANGLE_UNIT()
);
#56=(
NAMED_UNIT(*)
SI_UNIT(,.STERADIAN.)
SOLID_ANGLE_UNIT()
);
#57=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(0.01),#51,
‘DISTANCE_ACCURACY_VALUE’,
‘Maximum model space distance between geometric entities at asserted c
onnectivities’);
#58=(
GEOMETRIC_REPRESENTATION_CONTEXT(3)
GLOBAL_UNCERTAINTY_ASSIGNED_CONTEXT((#57))
GLOBAL_UNIT_ASSIGNED_CONTEXT((#56,55,#51))
REPRESENTATION_CONTEXT(‘ID1’,‘3D’)
);
#59=SHAPE_REPRESENTATION(‘Document’,(#60,#66),#58);
#60=AXIS2_PLACEMENT_3D(,#78,#67,#68);
#61=AXIS2_PLACEMENT_3D('',#79,#69,);
#62=AXIS2_PLACEMENT_3D(‘’,#80,#70,);
#63=AXIS2_PLACEMENT_3D('',#81,#71,);
#64=AXIS2_PLACEMENT_3D(,#84,#72,#73);
#65=AXIS2_PLACEMENT_3D(,#87,#74,#75);
#66=AXIS2_PLACEMENT_3D($,#88,#76,#77);
#67=DIRECTION(‘’,(0.,0.,1.));
#68=DIRECTION(‘’,(1.,0.,0.));
#69=DIRECTION(‘’,(0.,0.,1.));
#70=DIRECTION(‘’,(0.,0.,-1.));
#71=DIRECTION(‘’,(0.,0.,1.));
#72=DIRECTION(‘’,(0.,0.,1.));
#73=DIRECTION(‘’,(1.,0.,0.));
#74=DIRECTION(‘’,(0.,0.,1.));
#75=DIRECTION(‘’,(1.,0.,0.));
#76=DIRECTION(‘’,(0.,0.,1.));
#77=DIRECTION(‘’,(1.,0.,0.));
#78=CARTESIAN_POINT(‘’,(0.,0.,0.));
#79=CARTESIAN_POINT(‘’,(0.,0.,30.));
#80=CARTESIAN_POINT(‘’,(-62.5,-62.5,0.));
#81=CARTESIAN_POINT(‘’,(-62.5,-62.5,60.));
#82=CARTESIAN_POINT(‘’,(50.,0.,0.));
#83=CARTESIAN_POINT(‘’,(50.,0.,60.));
#84=CARTESIAN_POINT(‘’,(0.,0.,0.));
#85=CARTESIAN_POINT(‘’,(50.,0.,0.));
#86=CARTESIAN_POINT(‘’,(50.,0.,60.));
#87=CARTESIAN_POINT(‘’,(0.,0.,60.));
#88=CARTESIAN_POINT(‘’,(0.,0.,0.));
ENDSEC;
END-ISO-10303-21;