Can’t do spline

[ksporry]

Why can’t I do a spline?

 I’m trying to draw a curved line within a 2D square in a 3D model. For some reason the spline curve defaults to a random 3D curve and doesn’t follow the points I click. 

you can see a video of what I mean here. I’m sure there is a simple explanation for this. 
nite, I’ve tried moving the square away from the rest of the drawing so that the spline only has the square to deal with but that doesn’t have any effect. I can only draw a spline that follows my points when I only draw the spline in an empty part of the space. 

https://youtu.be/oMnlf-fbsDs

[imadHabash]

Hi,

>>  I’m trying to draw a curved line within a 2D square in a 3D model

I've just seen a 2d model NOT a 3d model in your attached movie , isn't it ? 

would you try to type UCS command >> World . then type PLAN command >> double enter .

any changes ?

[ksporry]

I’m not sure how to explain it without just sending my entire model. 
basically I have several 3D components in this workspace. 
the view is 2D and some of it are 3D shapes. 
I suspect the problem relates to my other problem on random placement of points in Z direction. 
it’s rather bizarre because if you look at the screenshots attached to this reply, you can see how the selected/highlighted polyline is in a 3D space, whilst in fact, I started those lines using the very bottom magenta lines you see on the bottom of the cyan 3D object. 

[imadHabash]

turn OFF Osnap and 3Dosnap [ F3 and F 4 ] , any changes ?

[ksporry]

No change. Behaves the same. 

I can redraw this if necessary, but I’ll need to know how I can draw in an XY plane with a constant Z value. There’s supposed to be an object snap option to set “replace z value with current elevation”. However, I’m unable to find it. The instructions from the knowledge database are wrong, as the options screen does not contain this option. 

for info, the way I draw 3D models is by drawing 2D views, extrude those, and then apply Union/substract/intersect. So when I draw in an XY plane, I want all z values to be the same. 

[Kent1Cooper · Accepted solution]

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@ksporry wrote:

.... There’s supposed to be an object snap option to set “replace z value with current elevation”. However, I’m unable to find it. .... 

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That's the OSNAPZ System Variable.

[leeminardi]

Why are you drawing a spline when all the line segments are straight?  I would recommend you do one of the following:

1.  Create individual lines from point to point.
2.  Create a 3Dpolyline.
3. Define a UCS that contains the 2D geometry and then create a polyline.  Note, when you create a polyline the first vertex will define the plane it lies on. The other vertices of the polyline with lie on a plane parallel to the active UCS but with the same elevation as the first vertex.

What I see in your video is that you are defining Fit points for the spline that have different depth (Z) values.  As you define successive Fit point the spline needs to wrap around in 3D space to pass through the next Fit point.  The lower the degree of the spline the more radical the curve will become as it tries to fit the specified data.  If you want to create a spline that has sharp corner you could define several (3 for a cubic spline) Control Vertices where you want the corner but I think this would be getting too complicated for what I understand you  are trying to model.

[j.palmeL29YX]

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@ksporry wrote:

... how to explain it without just sending my entire model. 

 

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Why you don't do it?

Of course you can delete everything that does not affect the problem.

[ksporry]

Thanks Kent1Cooper, osnapz=1 did do the trick and allowed me to draw splines.