Base point block

Hi,

I was wondering: is there a way to retrieve/change the base point of a "simple" block? First I thought "vla-get-Origin" or "vla-put-Origin" would do the trick, but then I discovered that the "origin"-property was not available for the blocks I selected.

Thanks for any help,

Stef

 

A block has an origin.

A block-reference has an insertionpoint.

AFAIK
If the block was created with the block command,
it should have an origin of (0.0 0.0 0.0)

The only time I have seen the origin differ from
'(0.0 0.0 0.0) is for an xref attachment that had
an insbase or base set to something different.

"vla-put-Origin" would do the trick, but then I discovered that the "origin"-property was not available for the blocks I selected.

 

Agreed, and that's an important distinction. You can extract the insertion
point of a block from its association list / dxf codes. But I don't think
you can extract the relationship between that and the entities that make up
the block. And I don't think you can change that relationship by way of
association values. You can change the value of the insertion point of a
block reference, which would MOVE the block in the drawing, but wouldn't
change the defined origin base point in relation to its pieces.

ONLY if you accept that as the offered default base point in the Block
dialog box. There's a "Pick point" button to set an insertion base point
that makes some sense in relation to the pieces. 0,0,0 is a pretty useless
origin point for most blocks made of elements drawn at some
out-in-the-drawing location, as I suspect most blocks are. Leaving it at
0,0,0 instead means (in almost all cases) you most likely won't be able to
drag the block visually into place when you insert it.

I don't EVER leave a block's (or a Wblocked drawing's) insertion point at
0,0,0 unless it's something like a sheet border and title block drawing, or
maybe if I'm in some temporary drawing only for the purpose of making things
and Wblocking them out, so I might build them deliberately around 0,0,0.
What good is an insertion base point if it doesn't have some logical
relationship to the elements in it (like the center of a circular tree
block, or the midpoint of the wall side of a bathroom lavatory)?

Even when you make a new drawing with Wblock, if you select a logical
location for its insertion base point, that location does NOT become 0,0,0
in the new drawing. It remains where it was in the drawing out of which you
Wblocked it. It is saved as the variable INSBASE.

"simple" block? First I thought "vla-get-Origin" or

"origin"-property was not available for the blocks I selected.

I haven't found any way to change the origin point of a block definition in
Refedit or anything. I think you might have to explode the block and
redefine it with a new insertion base point. Or in Refedit, you COULD
record the insertion point, then select all the elements of the block and
move them to a different position in relation to that point, then save the
changed block definition.

Kent Cooper, AIA

 

Hi Kent. See below.

[db]The block reference has no entities of its own. To translate coordinates
between the block reference and the block definition, use the trans function
or its activeX equivalent.

[db]NOT true. Before posting, I created a block and chose the insertion
point at (2,2,0). After inserting the block, I examined the origin
property of its block definition. It was 0,0,0. The block command
does the translation during the block creation process.

[db] I always try to avoid using insbase and base to control a drawings's
insertion point because it *ALWAYS* causes problems with trimming
and extending otherwise (due to an ACAD bug present since trimming and
extending with xref entities was made possible). Instead, I move
all objects from where the insertbase would have been to 0,0,0. That
practice has proved very satisfactory. Avoid the temptation to use insbase
or base.

[db] After Wblocking objects, I always open the drawing and use my IBA
command to shift all objects from the insbase to 0,0 and set the insbase to 0,0.
Otherwise, if the drawing is ever xrefed, instead of inserted, the trim and
extend commands do not work.

[db](vla-put-origin ...) will change the origin of the block. But wblocking
and changing it in its own drawing would probably be more intuitive to most drafters.

 

To add to my responses:
In 2004, wblock creates a drawing with the insbase set to whatever
origin the user picks during the wblock command.

In 2005, wblock creates a drawing with insbase=0,0,0 and the blocks
shifted so that the insertion point selected becomes the 0,0,0 point in
the new drawing. This is probably Autodesk's response to the xref
trim/extend problem.

I am not sure about earlier versions and their block/wblock behavior.
It would be prudent to test each version before making other
assumptions.

Regards,
Doug

<snip>

 

O yes, right. Keeping the distinction between a "block" and a "block-reference" in mind, then my original question should have been: is it possible to change the origin of a block. And by that I hoped there would be a solution without exploding and redefining the block. You know, I just hoped Vlisp or VBA would have a function to directly access the origin as a property or something.

But apparently that is not the case. Ken, now you've given me some new food for thought: how to use "refedit" through code. I'm sure you guys know how to do that, but please don't tell the answer. I'd like to try to find out myself first.

Thanks for the help!

Stef

 

Stef,

You can do it like this. There's no provision here to modify the Z value, though
easily added. And I don't know what method you had in mind for specifying the new
origin point. For instance you might ask for distance and angle.

I appreciate why you might want to do it. Sometimes we have a drawing used only to
create lots of blocks. An insertion (origin) point might need to move. I'd rather not
explode just to do that. The fact the block reference would move is of no concern in
this drawing.

Joe Burke

;; modify a block definition origin (insertion) point
;; note: existing block references will move
(defun c:BlockModInspt ( / doc blocks blk nm org xoff yoff )
(and
(setq doc (vla-get-activedocument (vlax-get-acad-object)))
(setq blocks (vla-get-blocks doc))
(setq blk (vlax-ename->vla-object
(car (entsel "\nSelect block: "))))
(setq nm (vlax-get blk 'Name))
(setq blk (vla-item blocks nm))
(setq org (vlax-get blk 'Origin))
(princ (strcat "\nExisting origin: " (vl-princ-to-string org)))
(setq xoff (getdist "\nEnter X axis offset "))
(setq org (mapcar '+ (list xoff 0 0) org))
(setq yoff (getdist "\nEnter Y axis offset "))
(setq org (mapcar '+ (list 0 yoff 0) org))
(not (vlax-put blk 'Origin org))
(not (vla-regen doc acActiveViewport))
(princ (strcat "\nNew origin: "
(vl-princ-to-string (vlax-get blk 'Origin))))
)
(princ)
)

mind, then my original question should have been: is it possible to change the origin
of a block. And by that I hoped there would be a solution without exploding and
redefining the block. You know, I just hoped Vlisp or VBA would have a function to
directly access the origin as a property or something.

thought: how to use "refedit" through code. I'm sure you guys know how to do that,
but please don't tell the answer. I'd like to try to find out myself first.

 

Joe,

Thanks for the code! With some changes it seems like this will do what I had in mind. "Some changes", because I intended just to ask for the new origin point.

Why I wanted to do all this: sometimes I "clone" existing block-references, in order to create a new similar block with some changes. But, if I edit the clone, the origin stays where it was in the original, although it does not necessarily relate to the newly edited entities any more. It might, for instance, suddenly fall somewhere outside the block.

thanks again!

Stef

 

Stef,

You're welcome.

If you intend to ask for a point (getpoint) to define the new origin, keep in mind a
block definition has its own coordinate system. Usually referred to as the OCS of the
block.

So to make this work right you might do this. Move the block reference so its
insertion point is at 0,0,0. Make sure you are in WCS because getpoint returns a UCS
point. Then use what I posted to change the X , Y and Z origin values based on what
getpoint returns. That will result in a block definition with an insertion point
that's not (0.0 0.0 0.0). Not typical, but I don't think it would cause any problems.

Another way would be to translate the point returned by getpoint to the OCS of the
block. That can get pretty complicated. You wouldn't have to move the block to 0,0,0.
But you would need a function which returns an inverse matrix (inverse of what
nentselp returns given a block reference) and another function which translates the
point based on the inverse matrix.

John Uhden has posted functions which do these things. But I don't see any reason to
get into that stuff if you find the first method I suggested works OK.

Let us know how it goes.

Joe Burke

mind. "Some changes", because I intended just to ask for the new origin point.

order to create a new similar block with some changes. But, if I edit the clone, the
origin stays where it was in the original, although it does not necessarily relate to
the newly edited entities any more. It might, for instance, suddenly fall somewhere
outside the block.

 

Stef,

Can you post your new code? I would like to change the block insertion point of a block I have inserted in various locations in a drawing.