Unnatural twisting on 'mesh renderered' splines

[jibijib]

Why does this twisting occur on the last version of Max for splines with 'enable in viewport' enabled?

I've only seen this happen in  2024, if you create a spline with a number of corners, it does this weird twisting on the mesh that is only cured by adding a chamfer to a corner or sometimes adding a point halfway across a segment?

[Byteman]

It can be due to a number of settings or all in combination:

• To achieve curved splines you need either enough number of vertices or to set the interpolation value to some value other than 0 to add in between steps between vertices. (Defaults to 6)
• Also the vertex attributes should be set to any value other than Corner. (Smooth, Bezier or Bezier Corner) Segments also have similar attributes Line or Curve. They should have been set to Curve, not Line.
• Finally there is an Optimize parameter which overrides the interpolation setting if the segments are close to a Line than a Curve by a threshold level. It prevents the creation of unnecessary interpolation steps if the segments are linear.

As a final tip, vertices although being only a point in space they can be rotated and cause twists. Keep that in mind, too. 

Attributes for Vertices or Spline Segments can be accessed by right clicking the correspondin sub-object. (Vertex attribute set as Corner is visible in the upper left quad menu in the image)

Remember to set the Enable in Render option along with the Enable in Viewport to make the splines renderable.

[jibijib]

Thanks for replying, I know the above and I've been doing splines for years but wondering why it has suddenly changed as I've never had a problem with this before?

[Byteman]

@jibijib Is your problem only the twisting?

May be you should consider using Sweep modifier or Loft compound object which has options to straighten corners. 

May be adding a tiny chamfer to the 2nd vertex (after the twisted one) might give the spline to have a chance to behave as you like.

You may also send the object over to look for a remedy together.

[3dtasarimokulu]

I made video for you

[jibijib]

Thank you for going to the effort of doing that 3dtasarimokulu - I think that is the same as refining the spline, which corrects it, if you add a vertex on any length of segment, it will correct the direction.

It has only started doing this in version 2024