Flattening 3D splines

Can anyone point me toward to routine that will successfully flatten 3D
Splines.

We sometimes get surveyors drawings with contours drawn this way, and
neither FLATTEN nor another utility I have tried FLATTEN.LSP will work.

thanks

Keith

 

I'm not sure why, it wouldn't be hard to generate a 2d spline
I mean wouldn't you just step through all the vertices and trans the global
to the current ucs, set the z to 0, and trans back to global.

--
Princess Jamie,

Life shrinks or expands in proportion to one's courage.
- Anais Nin

| Can anyone point me toward to routine that will successfully flatten 3D
| Splines.
|
| We sometimes get surveyors drawings with contours drawn this way, and
| neither FLATTEN nor another utility I have tried FLATTEN.LSP will work.
|
| thanks
|
| Keith
|
|
|
|

 

According to the follow website, they have a lisp routine that would help
you ...there is a contact email on the page.
http://ourworld.compuserve.com/homepages/johndavis/autocad.htm

LEDIT.lsp

Allows the following operations to be performed on sets of polylines:
reverse direction; create a single polyline from two or more polylines (the
endpoints of the polylines need not be touching); incline a 2d polyline
using an elevation for the start of the line and a fixed gradient or
endpoint elevation; flatten a 3d polyline to a 2d polyline.

HTH

 

Keith,

Assuming you mean flatten the control points of a spline, something like this might
do the trick. Barely tested, and not exactly elegant.

Joe Burke

(defun c:FlattenSpline ( / ent vobj ctrlpts pt reslst )
(setq ent (car (entsel "\nSelect spline: ")))
(setq vobj (vlax-ename->vla-object ent))
(setq ctrlpts (vlax-get vobj 'ControlPoints))
;(print ctrlpts)
(repeat (/ (length ctrlpts) 3)
(setq pt (list (car ctrlpts) (cadr ctrlpts) 0.0))
(setq reslst (cons pt reslst))
(setq ctrlpts (cdddr ctrlpts))
)
(setq reslst (apply 'append reslst))
;(print reslst)
(vlax-put vobj 'ControlPoints reslst)
(princ)
)

 

Flatten usually works. You may need to explode the spline once. There is an old command; CHANGE, Properties, Elev - set to 0.

 

Joe -

Many thanks - it may not be 'elegant', but it works and gives enough
information for an inexperienced lisper such as myself to modify it to do
the FitPoints as well and loop it for a selection set. That's all I needed.

Thanks very much.

Keith

 

Hi Keith,

Just for curiosity, why would you want to do this dumbing down of the data
in the drawing?

--


Laurie Comerford
CADApps
www.cadapps.com.au

 

Laurie

We would keep a copy of the 3D original. We are not using the 3D data for
the particular tasks in hand and users find that they are unwittingly
producing distorted 2D drawings by snapping to 3D points. (In turn getting
all sorts of problems ranging from inability to fillet and trim lines which
appear to be in the same plane but aren't becuase they have snapped to a 3D
point, to inaccurate measures and dimensions etc).

It has always amazed me that with Autocad you have to buy a 3rd party add on
(as far as I know) such as Flatland, to force new geometry to 2D. Staff who
have used Microstation tell me this part of the basic functionality of that
program.

Keith

 

Keith,

You're welcome. Glad I could help.

Forgive me if I'm stating the obvious. A word of caution if you use the code in a
loop to process multiple splines. The reslst var may need to be reset (setq reslst
nil) on each pass to avoid adding to an existing list.

Joe Burke

 

Hi Keith,

Thanks. I never use splines, so had no idea what awkward creatures they
are. It provided an interesting challenge.

Here is some VBA code which will flatten all splines to zero. As always
watch for word wrap.

You can change the layers selected by replacing the "*" with something like:
"Layer1,Layer2,MyLayer*"

--


Laurie Comerford
CADApps
www.cadapps.com.au

Sub FlattenSpline()
Dim oSpline As AcadSpline
Dim i As Long
Dim ssObjects As AcadSelectionSet
Dim vPt As Variant
If SelectObjectsOnLayer(ssObjects, "SPLINE", "*") > 0 Then
For Each oSpline In ssObjects
With oSpline
For i = 0 To .NumberOfFitPoints - 1
vPt = .GetFitPoint(i)
vPt(2) = 0
.SetFitPoint i, vPt
Next i
.Update
For i = 0 To .NumberOfControlPoints - 1
vPt = .GetControlPoint(i)
vPt(2) = 0
.SetControlPoint i, vPt
Next i
End With
Next
End If

End Sub

''''''''''''''''''''''''''''' '''''''''''''''''''
Public Function SelectObjectsOnLayer(ssObs As AcadSelectionSet, spObjectType
As String, spLayer As String) As Long
On Error Resume Next
Dim FilterType(0 To 1) As Integer
Dim FilterData(0 To 1) As Variant
Dim sNumber As String
FilterType(0) = 0: FilterData(0) = spObjectType
FilterType(1) = 8: FilterData(1) = spLayer
' The line below will create an error if the SSET doesn't exist
' or delete it if it does exist.
' The On Error will allow the program to continue and create the set
ThisDrawing.SelectionSets.Item("SSET").Delete
Set ssObs = ThisDrawing.SelectionSets.Add("SSET")
ssObs.Select acSelectionSetAll, , , FilterType, FilterData
SelectObjectsOnLayer = ssObs.Count
Exit Function

SOLErrorHandler:
Err.Clear
SelectObjectsOnLayer = 0
End Function ' SelectObjectsOnLayer()

 

Keith,

A bit of trivia I noticed while playing with this. If a spline object containing
control points at Z values other than zero is copied, the control points are
automatically flattened. Of course, the same is not true for fit points.

So to flatten control points given multiple splines, I think you could just copy the
splines in-place, and delete the originals.

Joe Burke

 

I'm pretty sure that Fit points are computed, and the control
points are the only thing you need to change.

 

Hi Tony,

That would make sense as the first trials of the code didn't work and I had
to swap the order of the two loops with which I processed the two groups of
data.

--


Laurie Comerford
CADApps
www.cadapps.com.au

 

Guys -

thanks very much! I managed to modify the code kindly provided by Joe
Burke, so that a selection set was processed. The routine processed the
control points and then the fit points for each entity. Strangely, it would
always flatten a single spline, but would seldom process a full selection
set - maybe that was do with the order of processing control & fit points.

Your routine looks rather more robust with the luxury of error handling (a
bit beyond me to write!).

Contributors to this NG have helped me so much over my decade of Autocad
use. Thanks to everyone!

Keith

 

Keith,

I can't know without seeing your code. But I suspect the problem you mentioned, "it
would always flatten a single spline..." might be caused by not paying attention to
my message regarding resetting the reslst var to nil inside a loop.

That would produce the effect you mentioned. The first spline would be processed as
expected. The second spline and those following would fail because the number of
points in reslst would accumulate. Thereby no longer corresponding to the number of
points contained in a spline being processed, within a loop.

Joe Burke