# Modelling with bezier curves.

I’ve been modelling a DB bzf 761 doppelsteuerwagen (Dostos STW) for Open Rails on and off for a while.

Lately, I’ve come across a limitation with the bezier curves which I cannot overcome with the current tools supplied within blender, and I’d like some advice on how to overcome this problem.

Currently, I’m trying to model the interior stairs of the 761 from scratch, using bezier curves as they define geometry very well, and very quickly with ease.

The problem comes up with circles.

The problem with this, would be the handles
http://wiki.blender.org/index.php/Doc:2.6/Manual/Modeling/Curves#Editing_Bezier_Curves
As soon as I modify the handles, the circle deforms and it becomes oddly - shaped.

For example: It’s impossible to create a perfect arc other then ones which are a multiple of 90 degree ones like you can do in Inkscape.

This creates problems when creating walls which arc round, using meshes sin’t that much better to use either, since you can’t achieve the precision like bezier curves can.

Another problem, would be angling with respect of the nodes.

For example: Imagine an arc along a horizontal plane, it would appear like a flat line.

And then, lets try to move the one of the nodes up.

Here’s the same curve in 3D view

Then, an Inkscape representation of the desired method:

The desired effect:

It’s not exactly possible to achieve that with the current tools without distorting the circle using rotation and scaling, which leads to inaccuracies.

Can someone help me with these problems as they’re quite hard for me to solve with the tools that I current have?:eyebrowlift:

Before subdividing, set handles types to Free.

### Attachments

Yeah, and then you’ve still got the problem of choosing where to “cut” the bezier curve, Subdivide doesn’t exactly let you choose where to cut it.

But, thanks for the quick reply.

Yes. You can convert meshes to curve also and draw with Inkscape and export to blender to curves (.svg).

But the thing is, is that the same problems exist because blender import .SVG images as 2D objects (limitations on the file type), so when you import them, the problem with changing the angle of the bezier curve import without changing the aspect ratio from a top-down perspective, which has to be done completely in blender.

Besides, if I have to resort to importing bezier curves from another program, wouldn’t that mean blender has a deficiency / lacking a few features?