Autodesk Survey Products

[#1]

how do u draw a spline in 3d. we are trying draw linework with a spline. this works in 2d but does not create a breakline.

[#2]

Hi MJONES1924,

You draw splines in Civil 3D with the normal AutoCAD Spline command.
However, Civil 3D does not recognise a spline for any purpose, so if you
wish to get Civil 3D information from a spline, the simple answer is -
you can't.

The slightly more complex answer is that you can convert the spline to a
polyline and get data from the polyline.

Regards


Laurie Comerford

MJONES1924MJONES1924 wrote:
> how do u draw a spline in 3d. we are trying draw linework with a spline.
> this works in 2d but does not create a breakline.

[#3]

so how do u convert a spline to a polyline?

[#4]

Hi MJONES1924,

Some ways.

* Draw it as a polyline first time.
* Trace over it as best you can.
* Search the web for conversion programs.

I seem to remember that Terry Dotson has one at www.dotsoft.com



Regards


Laurie Comerford

MJONES1924 wrote:
> so how do u convert a spline to a polyline?

[#5]

I'm a surveyor, and this is the survey products
newsgroup, so I feel I can point out that I would hate to be given spline
geometry to set out: you sure you don't want to use polylines with filleted
arcs?

I remember 6 years ago when I was the project
surveyor for a defence accommodation job: the architects supplied autocad
drawings of carparking and access roads with splines and levels here and there.
Had to use a bob-cat to shape it 'cause there were

no constant grades: cost went through the
roof.

Looked
lovely on the plan tho

size=2> 

Regards,

Jon Rasmussen

href="http://www.StringerSurvey.com">www.
size=3>StringerSurvey.com

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

<MJONES1924> wrote in message
href="news:6091478@discussion.autodesk.com">news:6091478@discussion.autodesk.com...

how
do u draw a spline in 3d. we are trying draw linework with a spline. this
works in 2d but does not create a breakline.

[#6]

well i have not used splines for contouring and breaklines in LLD2004. and if we did we use a spline, we would just trace right over the splines cause there were splines and they held no Z values so we created a breakline from point proxy. I did not know if AutoCADD did resolve this issue with 2007 and Civil3d apparently not. I have been using the Fit command in the Pedit command has been working fine, accept when we come to a ditch that is not so symetric. So i guess that next question is how do u make the fit command in the pedit command not make things so symetric not all cases need to be symetric like creeks ditchs and other natural objects.

[#7]

Are you saying you use the fit command on surveyed
breaklines?

Regards,

Jon Rasmussen

href="http://www.stringersurvey.com">www.
size=3>StringerSurvey.com

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

<MJONES1924> wrote in message
href="news:6093951@discussion.autodesk.com">news:6093951@discussion.autodesk.com...

well
i have not used splines for contouring and breaklines in LLD2004. and if we
did we use a spline, we would just trace right over the splines cause there
were splines and they held no Z values so we created a breakline from point
proxy. I did not know if AutoCADD did resolve this issue with 2007 and Civil3d
apparently not. I have been using the Fit command in the Pedit command has
been working fine, accept when we come to a ditch that is not so symetric. So
i guess that next question is how do u make the fit command in the pedit
command not make things so symetric not all cases need to be symetric like
creeks ditchs and other natural objects.

[#8]

yeah i am using the fit command on the survey lines is that wrong?

[#9]

A true 3d spline is very good and goes thru the points and AutoCAD can not do it. AutoCAD only do a best fit between the points like for chemistry report or for architects, but for surveyors they need it to go thru the points. It is very easy to program but they choose not to. I tried to give the math and algorithm in the early 90’s but they did not care about surveyor and evident by release 2009.

[#10]

Hi
size=3>white40,

Your comments seemed unusual to me and not within
my experience so I looked up Wikipedea:

<Quote from Wikipedea>

"In
href="http://en.wikipedia.org/wiki/Mathematics">mathematics, a spline
is a special
href="http://en.wikipedia.org/wiki/Function_(mathematics)">function defined
piecewise
by
href="http://en.wikipedia.org/wiki/Polynomial">polynomials. In
title=Interpolation
href="http://en.wikipedia.org/wiki/Interpolation">interpolating problems,
title="Spline interpolation"
href="http://en.wikipedia.org/wiki/Spline_interpolation">spline
inte... is often preferred to
href="http://en.wikipedia.org/wiki/Polynomial_interpolation">polynomial
interpolation because it yields similar results, even when using low degree
polynomials, while avoiding
href="http://en.wikipedia.org/wiki/Runge%27s_phenomenon">Runge's phenomenon
for higher degrees.

In the
href="http://en.wikipedia.org/wiki/Computer_science">computer science
subfields of
href="http://en.wikipedia.org/wiki/Computer-aided_design">computer-aided
design and
href="http://en.wikipedia.org/wiki/Computer_graphics">computer graphics, the
term spline more frequently refers to a piecewise polynomial
class=mw-redirect title="Parametric curve"
href="http://en.wikipedia.org/wiki/Parametric_curve">(p...
title=Curve href="http://en.wikipedia.org/wiki/Curve">curve. Splines are
popular curves in these subfields because of the simplicity of their
construction, their ease and accuracy of evaluation, and their capacity to
approximate complex shapes through
href="http://en.wikipedia.org/wiki/Curve_fitting">curve fitting and
interactive curve design.

The term spline comes from the flexible
href="http://en.wikipedia.org/wiki/Flat_spline">spline devices used by
shipbuilders and
href="http://en.wikipedia.org/wiki/Technical_drawing">draftsmen to draw
smooth shapes."

<End Quote from Wikipedea>

Within this definition it is quite clear that a spline does not pass through
the control points.

It is now over 50 years since I first started doing survey work and have
worked in the Civil/Survey field for that time.

The item by Jon was the first time I had ever heard of splines being used in
this area and it was quite clear from his post that the result was not one which
would lead anyone wanting to repeat that exercise.

What sort of survey work do you see needing a spline?

Regards,

Laurie Comerford

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

<white40> wrote in message
href="news:6135205@discussion.autodesk.com">news:6135205@discussion.autodesk.com...

A
true 3d spline is very good and goes thru the points and AutoCAD can not do
it. AutoCAD only do a best fit between the points like for chemistry report or
for architects, but for surveyors they need it to go thru the points. It is
very easy to program but they choose not to. I tried to give the math and
algorithm in the early 90’s but they did not care about surveyor and evident
by release 2009.