Scheme Extensions

 

 

Technical Article
Scheme is a public domain programming language, based on the LISP language, that uses an interpreter to run commands. ACIS provides extensions (written in C++) to the native Scheme language that can be used by an application to interact with ACIS through its Scheme Interpreter. The C++ source files for ACIS Scheme extensions are provided with the product. Spatial's Scheme based demonstration application, Scheme ACIS Interface Driver Extension (Scheme AIDE), also uses these Scheme extensions and the Scheme Interpreter.

rem:remove-faces

Action
Removes faces by growing adjacent faces to fill the gap.

Filename
scm/scmext/rem/rem_scm.cpp

APIs
api_remove_faces

Syntax
(rem:remove-faces face-list [box-h box-l] [lopt] [acis-opts])

Arg Types
face-list face | (face ...)
box-h position
box-l position
lopt lop_options
acis-opts acis-options

Returns
body

Errors
Some of the following errors result in an ENTITY, which indicates where the error occurs, being highlighted. The ENTITY type follows the error message below.
At least one face must be supplied or error REM_NO_FACE "no faces supplied"
Non-duplicate valid faces must be supplied from the same shell or error REM_BAD_FACE "face(s) supplied invalid, duplicate or from different shells"
Body must be manifold and solid or errors REM_NON_MANIFOLD "non-manifold edge detected" or REM_FREE_EDGE "free edge detected"
All faces in a shell or lump may be removed, so long as another shell remains, or error REM_LAST_SHELL "only shell in body would be lost"
Box must be valid if supplied, or error REM_BAD_BOX "invalid box supplied"
Adjacent faces must be able to combine to fill the gap left by the removed faces or error REM_NO_SOLUTION "gap cannot be filled"
Internal Algorithmic problems produce the error REM_INTERNAL "internal error"
 
Note that ENTITYs returned in the outcome standard_error_info object are highlighted.

Description
Removes an array of faces, growing the adjacent faces to fill the gap.
Curves and surfaces of edges and faces surrounding the removed faces, and which end in the user supplied box, are extended by a length approximately equal to twice the diagonal of the supplied box.
Similarly the intersections required to produce new edges and vertices, are limited by the size of the user supplied box.
Thus the user should supply a box likely to contain the changed faces. An overly large box will result in wasted computation. The default box is twice the body box of the original body.
Note that there may be no solution to the gap filling problem, or no solution using adjacent faces only. If the function detects these circumstances it issues an error and leaves the body unchanged.
Adjacent faces become infinite and with no loops will be deleted. An example of this would be when the tops of cylindrical bosses have the cylindrical face removed, leaving the remaining space unbound.
If the faces to be removed are isolated from one another, they are removed in the order supplied.
The body shells and lumps are corrected at the end of the operation, should they have been split.
New shells of different solidity to the original shell are deleted, for example, void shells made from a shell originally solid.

To have api_remove_faces heal gaps using adjacent and remote faces set option rem_use_rbi to TRUE, and api_remove_and_repair_body will be called.

Arguments
face-list identifies faces of a body to be moved.

box-h specifies one position defining a diagonal box for an intersection limit.

box-l specifies one position defining a diagonal box for an intersection limit. 

lopt is the local operation option.

acis-opts specifies options such as versioning and journaling.
Limitations
Body must be manifold and solid.

Some growing faces may shrink if necessary, but not so far as their boundaries. The healing process must be entirely within the faces adjacent to those removed.

No checks are made to see if the faces grown intersect with other non growing faces in the model. Checks that the growing faces intersect with one another are not rigorously done between unconnected regions of growing faces.

If the geometry of the edges lateral to the face(s) being removed do not have a well behaved extension, this can cause the scheme extension to fail.
; Example: Remove faces
; rem:remove-faces
; Create a block and blend it, then remove the face
(define block1
    (solid:block (position -25 -25 -25)
    (position 25 25 25)))
;; block1
(define blend (solid:blend-edges
    (pick:edge (ray (position 0 0 0)
    (gvector 1 0 1))) 10))
;; blend
; OUTPUT Original

(define remove (rem:remove-faces
    (pick:face (ray (position 0 0 0)
    (gvector 1 0 1)))))
;; remove
; OUTPUT Result

Figure rem:remove-faces
 
; Example: Remove and extend
; Clear the previous part
(part:clear)
;; #t
(define surf1 (splsurf))
;; surf1
(define ctrlpoints1 (list
    (position -25 25 20)
    (position 0 25 50)
    (position 25 25 30)
    (position -25 0 10)
    (position 0 0 50)
    (position 25 0 25)
    (position -25 -25 30)
    (position 0 -25 50)
    (position 25 -25 20)))
;; ctrlpoints1
(splsurf:set-ctrlpt-list surf1 ctrlpoints1 3 3)
;; #[splsurf 40255540]
(splsurf:set-u-param surf1 2 0 0 0)
;; #[splsurf 40255540]
(splsurf:set-v-param surf1 2 0 0 0)
;; #[splsurf 40255540]
(define uknots (list 0 0 1 1))
;; uknots
(splsurf:set-u-knot-list surf1 uknots 4)
;; #[splsurf 40255540]
(define vknots (list 0 0 1 1))
;; vknots
(splsurf:set-v-knot-list surf1 vknots 4)
;; #[splsurf 40255540]
(define face1 (face:spline-ctrlpts surf1))
;; face1
(define block2
    (solid:block (position -25 -25 -25)
    (position 25 25 25)))
;; block2
(define tweak (lop:tweak-faces (car (pick:face
    (ray (position 0 0 0) (gvector 0 0 1))))
    face1 #f))
;; tweak
; OUTPUT Original

(define remove (rem:remove-faces (pick:face
    (ray (position 0 0 0) (gvector 1 0 0)))
    (position -500 -100 -100)
    (position 500 100 100)))
;; remove
; OUTPUT Result

Figure.rem:remove-faces (Remove and Extend Faces)
 
; Example: Remove and split
; Clear the previous part
(part:clear)
;; #t
; Create a pyramid.
(define pyr1 (solid:pyramid 100 25 25 6 25))
;; pyr1
; Rotate pyr1.
(define rotate (entity:transform pyr1
    (transform:rotation (position 0 0 0)
    (gvector 0 1 0) 90)))
;; rotate
; Create a sphere.
(define sphere1 (solid:sphere (position 0 0 40) 25))
;; sphere1
; Unite the sphere with pyr1.
(define unite (solid:unite pyr1 sphere1))
;; unite
; OUTPUT United pyr1 and sphere1

; Create another pyramid.
(define pyr2 (solid:pyramid 100 25 25 6 25))
;; pyr2
; Rotate pyr2.
(define rotate2 (entity:transform pyr2
    (transform:rotation
    (position 0 0 0) (gvector 1 0 0) 90)))
;; rotate2
; Translate pyr2.
(define translate (entity:transform pyr2
    (transform:translation
    (gvector 0 0 80))))
;; translate
(define unite (solid:unite pyr1 pyr2))
;; unite
; OUTPUT United pyr1 and pyr2

(define remove (rem:remove-faces (pick:face
    (ray (position 0 0 40) (gvector 1 0 0)))))
;; remove
; OUTPUT Result

Figure.rem:remove-faces (Remove and Split Faces)
 
; Example: Remove and delete
; Clear the previous part
(part:clear)
;; #t
; Create a block.
(define block1
    (solid:block (position -25 -25 -25)
    (position 25 25 25)))
;; block1
(define cyl1
    (solid:cylinder (position 0 0 -5)
    (position 0 0 45) 20))
;; cyl1
(define unite (solid:unite block1 cyl1))
;; unite
; OUTPUT Original

(define remove (rem:remove-faces (pick:face (ray
    (position 0 0 30) (gvector 1 0 0)))))
;; remove
; OUTPUT Result

Figure. rem:remove-faces (Remove and Delete Faces)

rem:remove-wire-edges

Action
Removes an array of EDGEs in a WIRE body by extending the adjacent EDGEs and intersecting to fill the gap.

Filename
scm/scmext/rem/rem_scm.cpp

APIs
api_remove_wire_edges

Syntax
(rem:remove-wire-edges edge-list [box-h box-l] [lopt] [acis-opts])

Arg Types
edge-list edge | (edge ...)
box-h position
box-l position
lopt lop_options
acis-opts acis-options

Returns
body

Errors
Some of the following errors result in an EDGE(s) being highlighted, which indicates where the error occurs. The ENTITY type follows the error message below.
At least one EDGE must be supplied or error REM_NO_EDGE "no EDGEs supplied"
WIRE body must be manifold REM_NO_SOLUTION "non-manifold edge detected"
Box must be valid if supplied, or error REM_BAD_BOX "invalid box supplied"
Adjacent edges must be able to fill the gap left by the removed edgess or error REM_NO_SOLUTION "gap cannot be filled"
Internal Algorithmic problems produce the error REM_INTERNAL "internal error"

Description
The array of EDGEs supplied to the API must all belong to the same WIRE body, but do not have to connect.
The functionality of the API removes the EDGEs from the WIRE body, extends the neighboring EDGEs (naturally), and intersects to close the gap. If no intersection exists, then the API returns "gap cannot be filled".
The API, additionally, takes a bounding box as input. If an EDGE/EDGE intersection falls outside of the bounding box, then the API again, fails.
If the API detects either of these circumstances, it leaves the body unchanged.
If the intersection involves two identical curves such as straights, than a VERTEX is placed between the two EDGEs based on an average distance.

The API works on both open and closed WIRES. If an open WIRE is given and the EDGE to be removed is either of the EDGEs making up the ends of the WIRE, the EDGE will simply be removed from the WIRE body. If the WIRE body contains only one EDGE and that EDGE is asked to be removed, the WIRE body is deleted.

Arguments
edge-list identifies edges to be removed.

box-h specifies the end of intersection and extension box to be used.

box-l specifies the start of intersection and extension box to be used.

lopt specifies local operations options. NULL argument sets the default values.

acis-opts specifies options such as versioning and journaling.
Limitations
WIRE body must be manifold.

If the geometry of the EDGEs adjacent to the EDGE(s) being removed do not have a well-defined extension, this can cause it to fail.
(view:dl)
(part:clear)
(define wire1 (wire-body (list (edge:circular (position 0 0 0) 10 180 270)
                               (edge:linear (position 0 -10 0) (position 100 -10 0))
                               (edge:circular (position 100 0 0) 10 270 360)
                               (edge:linear (position 110 0 0) (position 110 25 0))
                               (edge:circular (position 100 25 0) 10 0 90)
                               (edge:linear (position 100 35 0) (position 0 35 0))
                               (edge:circular (position 0 25 0) 10 90 180)
                               (edge:linear (position -10 25 0 ) (position -10 0 0)))))

(top)
(zoom-all)

(define edges (list (list-ref (entity:edges wire1) 6)
                    (list-ref (entity:edges wire1) 4)
                    (list-ref (entity:edges wire1) 2)
                    (list-ref (entity:edges wire1) 0)))

(entity:set-color edges 1)
(rem:remove-wire-edges edges)

(entity:check wire1)

(part:clear)

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