Spline Normals (XZ orientation)

Hello,

After creating a 3d spline, be it from geometry/lathe/slide or manual positioning, I find that although the Normal [Y] directions [of the spline vertex] are correct, the XZ orientation around the normal flips 90 deg along the spline at various positions.
Should it be doing that?
Is that the reason the extrude always twists rather than being consistent along a 3d spline extrusion?

Thanks

Can you show that in a pic? I don't understand what is that you're talking about.

I wanted to create a simple sweep along a path, the path taken from a model edge.

If I was to use a spline as profile using "Slide", there is no control over the tangency direction, so instead, used a polygon for profile and used the "Extrude" function.

This is a quick example.

Polygon profile at start of path:-



On extrusion, there is a twist in the result, and not wanted/expected.



I know there is the option to add "Twist" which can correct the output, but could not understand why I was getting such a result, as there must be some underlying control of the "Roll axis" of the default extrusion.

So rather than guessing what the twist needed was to get an accurate result, I decided to add a number of cross sections to the path using "Snap_Position_Normal#", but found that when I did that, the "Roll"[the XZ directions in relation to the normal direction] of the cross section changed at various points along the path, causing the profile to abruptly rotate 90 deg. So to check further, I added a cross section to each point of the path using "Snap_Position_Normal#" The result showed that some of the cross section "Roll axis" changed direction at various points on the path:-



That result I find inconsistent, and not what I normally see in other 3d programs I have used.

Should be fine now.

Should be fine now.

It as fixed the problem with the flipping the orientation(roll) on the path itself, thanks. There are still problems with the flipping of the XZ orientation on the spline vertex, But and the problem remains with the "extrude"

So the extrusion should not be keeping orientation(roll) to path? and instead twist while extruding. Is that correct?

There are still problems with the flipping of the XZ orientation on the spline vertex

I think it is fixed.

Fixed for that specific example, yes, but problem still exists on some other constructed splines I have made.

I really do not know what tangency you are working to with the "Extrude" and "Slide> Use path curve tangent spaces". The result are no where near to what is shown by the "Snap_Position_Normal#"(even when those spline vertex tangency are consistent.)

Here is a quick, simple example:-

A 3d path. I have used "Snap_Position_Normal#" to check the orientation of the tangency of each point on path. That looks correct, and would expect a slide using those tangents to show a similar result.


But when using "Slide" the result is no where near. This is the result when option "Use path curve tangent spaces" is enabled:-

Can you send me the file of this example?

Example file sent.

Please check that again with the new update.

Certainly a massive improvement, many thanks.

I am seeing a slight error with alignment of spline to start of path, but looks like a possible problem with "Snap_align_normal#". I do have an example, but will see if I can find others and will send them to you by e-mail.

Best Regards,

-Steve

Can you send me that file?

I have sent that example file.

I have found some solutions. Please recheck them.

I do like the results I am seeing now, and are certainly (IMHO) what most users would expect.

I can cause some problems in extreme circumstances, but changing options corrects the slight problem I do see.

I also like the fact that I can create a cross section not on correct XZ orientation(around normal direction), and NVIL will now blend that with the rest of the slide using the paths tangency, very nice.

Excellent work, and many many thanks for taking the time to implement this.

[If I do find any issues, I will e-mail you example files.]

Thanks again,

Best Regards,

-Steve