topic interpolate spline from mesh in 3ds Max Modeling Forum

interpolate spline from mesh

mark_aldred — Mon, 23 Sep 2019 16:57:37 GMT

Imagine you have a mesh that used to be a spline but had a circular Sweep applied then was collapsed. Anybody know any tricks to get the spline back? I guess I need to put a vertice at the centre point of each loop? Any scripts or the like to help?

Thanks

Mark

Re: interpolate spline from mesh

miledrizk — Mon, 23 Sep 2019 17:21:26 GMT

Hi,

In the Editable Poly, go to the Edge subobject level and select the edges that make up the old

Spline shape. You can try double-clicking one edge to select the whole loop, you can also click the

Loop button in the selection rollout. If it's a ring of edges you want then click the Ring button.

Now, in the Edit Edges rollout click the Create Shape From Selection button, choose the option

Linear, give it a name(optional) and click OK. Now you have a spline shape as a separate object.

Re: interpolate spline from mesh

mark_aldred — Mon, 23 Sep 2019 17:25:43 GMT

Thanks, but unfortunately that won't do it because there are no edges that make up the old spline shape. The spline was given thickness, so I'm looking to get the line that runs through the middle.

Re: interpolate spline from mesh

leeminardi — Wed, 25 Sep 2019 01:32:35 GMT

If you have an editable poly and would like to extract a profile try the following:

Select the Edge sub-object and then working in the top view select and Edge that defines the profile of the lathed shape (that has been collapsed).
Click Slice Plane and Slice. Position the slice plane gizmo so that it is in the center of the object.
Now click Create Shape From Selection.
The resulting shape is a spline you can use to with lathe or other modifiers.

Re: interpolate spline from mesh

mark_aldred — Wed, 25 Sep 2019 12:26:01 GMT

Thanks, but it's not a profile I'm after.

Try this ....

1. create an ellipse

2. apply a sweep with a circular section to get a doughnut-like shape

3. collapse to editable poly

Now, how would I get the ellipse back? It's the line that runs through the centre of the sections.

I actually found a quick and dirty solution but it's not perfect. I selected the innermost egde loop, created a shape and scaled up. An accurate way to place a vertice in the middle of each section would be much better.

Re: interpolate spline from mesh

leeminardi — Wed, 25 Sep 2019 13:28:49 GMT

"I actually found a quick and dirty solution but it's not perfect. I selected the innermost egde loop, created a shape and scaled up. An accurate way to place a vertice in the middle of each section would be much better."

Using scale does not create an accurate result. Picture a long thin rectangle. Scaling it up yields a larger offset in the long direction of the original rectangle than inthe short direction. It would be better to choose the top or bottom isoline and remove it to form the centerline of the original sweep path. Working in a zoomed in front view of the shape I could easily select the isolines (edges) that define the path of the sweep and then remove is as a spline shape.

Re: interpolate spline from mesh

mark_aldred — Thu, 26 Sep 2019 05:58:29 GMT

Thanks for the help.

I actually chose the inner loop instead of this because top loop wasn't centre.

Scale the axes separately and the inner loop works fine.

I'd still like to find a better solution. Something like isolate all edge loops (sections), collapse to their centre points and use those vertices to create a spline.

Re: interpolate spline from mesh

miledrizk — Thu, 26 Sep 2019 10:38:16 GMT

Maybe you can try this (a little time consuming though):

1- Select each loop of vertices at a time, Right-Click the Scale uniform and set it to 0

On the left is the Original path, it will be used for comparison later

2- When finished, in the Edge sub-object level select one edge, click Loop, and use

The option "Create Shape From Selection", check the option Linear

On the left the extracted spline. To the Right the original Spline

3- I used the Align tool, with the Center - Center option to compare the two shapes

Both shapes aligned

Re: interpolate spline from mesh

mark_aldred — Mon, 30 Sep 2019 04:01:47 GMT

Thanks for the help.

That's exactly what I need to do, but I'd like to either find a short cut or automate.