Intersections & Cross Sections

Synopsis

obj = INTSEC/surf1,WITH,surf2[,TOLER,tl][,lsurf1,lpoint1,lsurf2,lpoint2[,VECT,x,y,z]][,IFERR,label:]

Description

Generates curves at the intersection of two single face surfaces (sheet bodies) and/or planes. In general, the curves go from edge to edge of the surfaces being intersected.

If the surfaces have been trimmed, the resulting surface intersection or cross section curves are trimmed to the trimmed edges of the surfaces and to any holes in the surfaces.

The intersection curves can be limited (or extended) by specifying suitable limiting surfaces, points, and a direction vector. Analytic intersection curves (lines, arcs, or conics) are produced where possible. Otherwise, the curves produced are B-splines. The resulting curves are returned as a group object, even if only one curve is generated.

Parameters

Parameter

Description

surf1

A previously defined single face surface (sheet body) or plane that is to be intersected with another surface or plane to produce the intersection curve.

WITH

Minor word indicating that the second single face surface is to be specified in the next field.

surf2

A previously defined single face surface (sheet body) or plane which is intersected with surf1 to produce the intersection curve.

TOLER

Minor word that indicates that a tolerance be used to create the intersection. If none is specified, the default is the value set in the Unigraphics option Preferences->Modeling. You can also read and set this tolerance using the GPA &DISTOL.

t

A numerical value greater than zero which is used to create the intersection curves. The system attempts to create intersection and cross section curves which differ from the true intersection curves by no more than this value.

lsurf1

An existing surface (sheet body) or plane which is used to limit the length of the intersection curve. The curve begins tracing where this surface intersects the two surfaces being intersected.

lpoint1

An existing point used to help determine the start point for the trace curve in cases of ambiguity.

lsurf2

An existing surface (sheet body) or plane which is used to limit the length of the intersection curve. The curve stops tracing where this surface intersects the two surfaces being intersected.

lpoint2

An existing point used to help determine the end point for the trace curve in cases of ambiguity.

VECT

Minor word that indicates that a vector be specified to control the direction of the trace for the intersection curve.

x,y,z

Numerical components of a vector which controls the trace direction of the intersection curve. The curve is traced in the direction that the vector points.

VECT,x,y,z need only be specified in cases where the direction of intersection may be ambiguous. For example, the direction from one limit point to another limit point on a spherical or cylindrical surface.

VECT,x,y,x has no effect if no limiting objects are used.

IFERR,label:

Specifies a label to which program execution jumps if an error occurs during intersection.

NOTE: In general, all intersection curves (or cross section curves) are created, unless limiting surfaces are specified.

The system may not find an intersection curve if the faces just touch one another and do not fully intersect. For example, this may occur in the case of a fillet sheet body and the faces being filleted.

Example

Creating an intersection between a ruled surface (RSURF) and a B-surface (BSURF). Limiting planes and points are specified to limit the surface intersection curve that is created. GRP is a group containing the curve.

Statement

GRP=INTSEC/RSURF,WITH,BSURF,PL1,PNT1,PL2,PNT2
INT1=&GENT(GRP,1)
UNGRP/GRP

Surface to Surface Intersection

Example

Demonstrates the cross sectioning of a trimmed cylinder (CYL1) with a plane (PL1). All cross section curves are created. A tolerance of 0.01 is specified. GRP is a group containing the curves.

Statement

GRP=INTSEC/CYL1,WITH,PL1,TOLER,.01
DO/ L10:, I, 1, &GCOUNT(GRP)
L10: ICRV(I) = &GENT(GRP,I)
UNGRP/GRP

Cross Section of a Trimmed Cylinder by a Plane

Parameter	Description
surf1	A previously defined single face surface (sheet body) or plane that is to be intersected with another surface or plane to produce the intersection curve.
WITH	Minor word indicating that the second single face surface is to be specified in the next field.
surf2	A previously defined single face surface (sheet body) or plane which is intersected with surf1 to produce the intersection curve.
TOLER	Minor word that indicates that a tolerance be used to create the intersection. If none is specified, the default is the value set in the Unigraphics option Preferences->Modeling. You can also read and set this tolerance using the GPA &DISTOL.
t	A numerical value greater than zero which is used to create the intersection curves. The system attempts to create intersection and cross section curves which differ from the true intersection curves by no more than this value.
lsurf1	An existing surface (sheet body) or plane which is used to limit the length of the intersection curve. The curve begins tracing where this surface intersects the two surfaces being intersected.
lpoint1	An existing point used to help determine the start point for the trace curve in cases of ambiguity.
lsurf2	An existing surface (sheet body) or plane which is used to limit the length of the intersection curve. The curve stops tracing where this surface intersects the two surfaces being intersected.
lpoint2	An existing point used to help determine the end point for the trace curve in cases of ambiguity.
VECT	Minor word that indicates that a vector be specified to control the direction of the trace for the intersection curve.
x,y,z	Numerical components of a vector which controls the trace direction of the intersection curve. The curve is traced in the direction that the vector points. VECT,x,y,z need only be specified in cases where the direction of intersection may be ambiguous. For example, the direction from one limit point to another limit point on a spherical or cylindrical surface. VECT,x,y,x has no effect if no limiting objects are used.
IFERR,label:	Specifies a label to which program execution jumps if an error occurs during intersection.