WCS OCS and bulge

The coordinates of a LWpolyline are in OCS. These can be translated to WCS
with the utility.TranslateCoordinates method.

But also the bulges of the arc-segments are relative for the OCS
coordinates. Does anyone know how to translate the OCS-bulge to WCS-bulge?

thanks,

Ad Brouwer

 

Ad, I believe you're confused about the meaning of the bulge.
The bulge is = tan (included angle /4)

 

I know how bulge works.

But when drawing a lwpoly with arc-segments in a UCS (or 3d-view) then the
coordinates and bulge are relative to the UCS (Normal <> 0,0,1).

With TranslateCoordinates(ptOCS, acOCS, acWorld, False, acEnt.Normal) you
can convert the coordinate from OCS to WCS, but the bulge is still relative
to the OCS.

You could reproduce this by:
-start a new drawing
-go to View -> 3D Views -> Right
-draw a LWpoly with at least 1 arc-segment
-list the created LWpoly and record the bulge
-go back to the top-view (you should see a straight vertical line)
-list the created LWpoly

You'll see that the bulge is the same, while the coordinates now are in WCS
(the Normal = 1,0,0)

When retrieving the the coordinates and bulge in vb these are in OCS
The coordinates cab be translated, but how to get the bulge in WCS.

Ad

 

I'm not sure I understand your question. As Jorge alluded to in his reply: the value of a bulge is not a coordinate (i.e. it is not dependent on any coordinate system).

 

Ad, the value of the bulge IS THE SAME, no matter the UCS.
Now, if you're talking about the projection on another UCS, then, that's not
the bulge, that's another story !!

 

Yes, I'm talking about the projection. The coordinates of a LWpoly are
always in its own UCS (the OCS). When I want to extract this kind of lines
in World coordinates (for conversion purposes), I have a problem. The
coordinates can be derived via TranslateCoordinates, but what about the
bulge? When the LWpoly has arcs in one plane, it can be a straight or
something else in another.

While typing this message, it hit me.
I Think, the only way to solve this, is to create a 3D poly from the LWpoly
by inserting extra vertexes in the arc-segments based on the OCS
coordinates/bulge and translate these coordinates to WCS.

What do you think about this, or is there another way?

greetz,
Ad Brouwer

 

Now, forget about the bulge !!! talk about the arc segment.
You can use the curve functions to get your coordinates.
These are available in LISP but not in VBA
so you'll need an add on to do this.

 

Thanks Jorge, but i'll go for the 3Dpoly option. I need it in VB(A), Lisp
isn't an option for me.