THIKEN ( body, front, back, check, tol, mxflts, oldtop, newtop, badtag, state,
===============================================================================
ifail )
=======
Thickens a sheet body into a solid
Receives:
KI_tag_body *body --- body to be thickened
<KI_dbl> *front --- thickness on front of faces
<KI_dbl> *back --- thickness on back of faces
KI_cod_logical *check --- level of checking required
<KI_dbl_distance> *tol --- tol of SP curve conversions
<KI_int_nitems> *mxflts --- maximum number of entities in badtag
Returns:
<KI_tag_list_entity> *oldtop --- original topology
<KI_tag_list_entity> *newtop --- new topology
<KI_tag_list_entity> *badtag --- entities which caused problems
KI_cod_rtof *state --- state of body after offset
KI_cod_error *ifail --- failure code
Specific errors:
KI_cant_thicken thickening failure
KI_unsuitable_entity Mixed body
KI_bad_tolerance proposed edge tolerance is too small
KI_not_sheet body is not sheet
KI_bad_thickness total thickness zero
Description:
The sheet 'body' is thickened by 'front' outwards (i.e. in the direction of
the face normal) and 'back' inwards. Either 'front' or 'back' may be
negative, but the total thickness must be non-zero.
Only manifold sheet bodies can be thickened.
Some edge geometry on the sheet boundary may have to be approximated by
SP-curves in order to generate a boundary curve on the offset faces. If this
is necessary, such edges will have a tolerance less than or equal to the
tolerance supplied through the 'tol' argument.
Two situations can give rise to changes in the topology :
1) Dealing with geometry which fails to offset. If it is known that the
offset surface of a face would be self-intersecting an attemp is made
to remove the face. For example, a blend may be removed from an edge.
The investigation of self-intersection is not exhaustive, however,
and it can occur that instances are not trapped.
2) Dealing with configurations which can be repaired. For instance an
edge may offset to a point or a face become absorbed into the body.
The extent to which cheking is applied to the body is specified by the
'check' argument. If 'check' is true then face-face checks are done on
the body in addition to default checks. For most applications setting
'check' false will give an adequate level of checking.
Thickening which would lead to a self-intersecting or non-manifold solid is
not allowed. Some of these cases will not be detected when face-face checks
are not done, in this case the resulting body will be invalid.
Boundary edges with the following curves on these surfaces will be treated
exactly :
Surface | Curve
-----------------------------------------
Plane | Line, Circle, Ellipse or B-curve
Cylinder | Line, Circle or B-curve equivalent
Cone | Line, Circle or B-curve equivalent
Sphere | Circle
Torus | Circle
Swept Surface or | Line, Profile curve or B-curve equivalent
B-surface equiv |
Spun Surface or | Circle, Profile curve or B-curve equivalent
B-surface equiv |
Thickening only handles the cases where each vertex on the boundary of the
sheet meets one of the following requirements. Either the vertex is smooth
(surface normals constant on all adjoining faces) or both adjoining boundary
edges must have curves of the types treated exactly (see table above) or the
thickening is into the angle of the edge (i.e. convex edges inwards only and
concave edges outwards only).
Each new face in the resulting body will have been generated by either
a face, an exterior edge or vertex in the original sheet. The pairs of
original faces, edges or vertices and corresponding new faces are
returned in the 'oldtop' and 'newtop' arguments. Both lists may
contain null tags where faces have vanished. If the total thickness is
positive the tag of a face in the original body will remain on the
front of the resulting body with the same sense otherwise it will be
on the back with the opposite sense.
The error reporting scheme comprises the three arguments 'badtag', 'state'
and 'ifail'. A non-zero 'ifail' is reserved for reporting unsuitable arguments
to the function and system errors.
Algorithmic failures where the item causing the failure can be identified
result in a zero 'ifail' and more specific information being returned in the
'state' argument and 'badtag'. For example, a thickness so large that any of
the surfaces could not be offset will return 'state' RTOFSO and the tags of
faces whose surfaces could not be offset in the 'badtag' list.
'state' refers to the validity of the item after modification and not to its
original validity. After such a failure 'body' may be corrupt and a rollback
should be performed. For this reason tags of new topology cannot be returned
in 'badtag' and the tags will refer to adjacent faces in the original body
supplied. For example if a new edge cannot be modified a 'state' RTOFEM is
returned and 'badtag' will contain the tag of a list of the two faces whose
offsets are to be used to find the new curve.
Possible values of 'state' and the contents of 'badtag' are :
Token | Tag(s) in | Meaning
| badtag |
-------|------------|-----------------------------------
RTOFOK | null | Body is OK
RTOFSO | face(s) | Surface failed to offset or face could not be deleted
RTOFVM | vertex | Failed to find new geometry for vertex
| list faces | Failed to find geometry for new vertex
RTOFEM | edge | Failed to find new geometry for edge
| list faces | Failed to find geometry for new edge
RTOFSS | edge | Failed to find side surface
RTOFSC | vertex | Failed to find side curve
RTOFVT | edge | Edge should have disappeared
RTOFFA | face | Face failed checks
RTOFSX | faces | Face-face inconsistency found
Notice that a successful execution of the thickening operation is indicated
by :
ifail returning KI_no_errors
state returning RTOFOK
