Can you draw a circle use a spline?

[Raggi_Thor]

And order can only be 5 or 6?

And you cant enter control points, only interpolation points?

So it's impossible to make a spline with 4 controlpoints, I always get 5?

[SEANT]

And order can only be 5 or 6?

And you cant enter control points, only interpolation points?

So it's impossible to make a spline with 4 controlpoints, I always get 5?

 

Autocad's implementation of splines is a bit off that of Rhino's. In Autocad, Control Points will always be FitPoints + 2. I believe this is to accomodate the Tangent vectors. So a Spline with 4 control Points would be avalable from a acad spline of only two points.

 

Another area of possible interest is the Splinedit-Fit Data-Purge option.

[Raggi_Thor]

Well, I tried a little more and have to say, buy Rhino if you need to draw and edit splines It costs less than ACLT.

[cnreader]

They are control points.

With nurbs of third degree, if you have three control points in line, the curve will touch that line.

 

When you select the curve, the control points will appear, but when you use command of spedit, there are more points appearing. what are they?

if you move them the shape of the curve will be changed, are they knots points?

[cnreader]

as I said above it has 6 points.

[cnreader]

In this cad, the degree seems fixed, cannt be changed.

right?

[Raggi_Thor]

http://download.mcneel.com/eval/?p=25

[cnreader]

Does the software learn easily?

[cnreader]

as I said above it has 6 points.

 

I noticed that the points are four in circle, six in ellipse, but when the object was broken, the point will be 7.

The points in cad2000 was called vertex.

When I select it, it display command, move vertex, next, etc. when I draw it, the shaple fo circle or ellipse will be changed.

But I still odd, how shall I use it to get the shape what I need.?

It seems the vertex is just the control point.

[Raggi_Thor]

If you know AutoCAD you will love Rhino :-)

NOTE: I am selling Rhino in Norway!

 

The big difference (in this matter) is that you can use all normal editing commands on the controlpoints. You don't need to start a command and type NEXT and so on to get to the point. Just select any curve, press F10 to turn on the points, select one or many points and move, rotate, scale, delete and so on.

 

I spent some time yestarday drawing splines in acad but I didn't manage to make a true circle. Is it possible at all? I almost got a half circle.

[SEANT]

If a circular Spline of degree 2 (order 3) were needed, and Rhino was not available, it could be generated with Autocad by jumping through some hoops.

 

For example:

 

Set SPLINETYPE system variable to 5

 

Command: _polygon Enter number of sides

proceed to make polygon (actually a Polyline) to the approximate size needed

 

Command: _pedit Select polyline or [Multiple]

select polygon Spline

 

A Quadratic (degree 2) Spline Fit 2DPolyline is generated.

 

Command: _spline

choose [Object] option and select 2DPoly

 

The poly is converted to a circular spline with 8 semi-regularly spaced Control Points. Fit Point data has been purged.

 

A _scale with [Reference] option may be needed to get the appropriate size.

[cnreader]

If you know AutoCAD you will love Rhino :-)

NOTE: I am selling Rhino in Norway!

 

The big difference (in this matter) is that you can use all normal editing commands on the controlpoints. You don't need to start a command and type NEXT and so on to get to the point. Just select any curve, press F10 to turn on the points, select one or many points and move, rotate, scale, delete and so on.

 

I spent some time yestarday drawing splines in acad but I didn't manage to make a true circle. Is it possible at all? I almost got a half circle.

 

Try this way,

select 4 control points to form a square. then select close, select a suit direction as it tangent direction. enter. you can find a circle in front of you. the key is selection a tangent direction at last.

[cnreader]

If a circular Spline of degree 2 (order 3) were needed, and Rhino was not available, it could be generated with Autocad by jumping through some hoops.

 

For example:

 

Set SPLINETYPE system variable to 5

 

Command: _polygon Enter number of sides

proceed to make polygon (actually a Polyline) to the approximate size needed

 

Command: _pedit Select polyline or [Multiple]

select polygon Spline

 

A Quadratic (degree 2) Spline Fit 2DPolyline is generated.

 

Command: _spline

choose [Object] option and select 2DPoly

 

The poly is converted to a circular spline with 8 semi-regularly spaced Control Points. Fit Point data has been purged.

 

A _scale with [Reference] option may be needed to get the appropriate size.

 

you mean select polygon command at first, then convert to spline?

[Raggi_Thor]

Thanks, interesting.

I think I forgot to change SPLINETYPE from 6 to 5.

[cnreader]

I download the rhino today, and it require too high to my computer. so I give up.

I thnk it will be easy use from your instruction. I hope to master the curve . becaseu every software has differnt operation way to it

[Raggi_Thor]

I don't know how much adverticement is accepted in this fourm, but you could look for other low cost or free 3D modellers also.

[cnreader]

I don't know how much adverticement is accepted in this fourm, but you could look for other low cost or free 3D modellers also.

 

its not ad. its a good suggestion instead.

yes thee are lots of free 3d modeling software. but many people recommand the rhino.

especially at nurbs .

[cnreader]

How do you use to use these curve generally?

I feel, as I study it, I cannt control it . I can modify its control point, but how to adjust knots positon?

[Raggi_Thor]

How do you use to use these curve generally?

I feel, as I study it, I cannt control it . I can modify its control point, but how to adjust knots positon?

 

In my Acad 2008 the interpolating points are there and can be stretched (moved), but they dissapear after I change SPLFRAME to 1 (ON) and modify a controlpoint.

[cnreader]

These are drawed by another software.

one is cycle and another si sine wave. drawed by b-spline.