Spline modeling donut

[Danmitch1]

Hi, Its possible that im searching for the impossible but can you apply a surface modifier to a donut (converted to an editable spline) without it filling the inner circle?

Im trying to build a tube

[10DSpace]

@Danmitch1 

Is there a reason you don't you start with the tube primitive and convert to an editable poly?

You can also convert the donut shape to an editable poly and extrude the donut poly. 

 Either way you get to a similar place depending on the number of segments you select for the tube.

[Danmitch1]

My goal (perhaps impossible) was to create a model 100% using splines with surface modifiers. 

I realize I could finished the model and use a Boolean subtraction to cut the hole but like I said, I wanted to complete the model 100% out of splines and surface mods. Maybe not possible?

Thanks for your reply!

Dan.

[10DSpace]

@Danmitch1 

Sorry, but if you are insisting on the constraint of no other tools in max other than spline and surface, then I do not know a way to do specifically what you want to do.  The surface modifier seems oriented to completely covering external surfaces of spline cross sections and I do not know a way of specifying selective coverage (and in your case, selectively changing/flipping normal direction across individual segments) to guide the surface modifier away from complete coverage with a single surface normal orientation for the entire surface.      That is where I would reach for editable poly modeling tools, personally.    Maybe someone else here knows a way with spline and surface tools alone.

[Danmitch1]

Yeah thats what I was afraid of. I was thinking it was a threshold thing but if I increase the threshold of the surface, parts I want a surface on start to disappear..

There must be a way of creating holes in the surface other than converting to editable poly.

Thanks for your input!

Dan.

[10DSpace]

@Danmitch1 

There must be a way of creating holes in the surface other than converting to editable poly.

Well in thinking further about the issue, if you separate the donut into left and right and inner and outer halves,

then the surface modifier will leave the hole you want.   

You could then use a copy of the individual donut sections with cross sections created from outer to inner to cap the top.  This gets around the surface modifier's behavior of closing the entire surface, because essentially you are surfacing cross sections based on arcs which are not closed shapes.  Hope this helps.

[Danmitch1]

Thanks for your efforts, as this is a good solution i failed to mention this is to be 3d printed. It will need to be one mesh.

[leeminardi · Accepted solution]

Convert the outer spline profile to a NURBS then attach the inner profile.  YOu can then add the Extrude modifier and the shape will be capped.

Note, an editable poly can be saved as an STL file for 3D printing. 

[Danmitch1 · Accepted solution]

Oh ok, that would work then. I was wanting to stay out of editable poly mode and use only splines for super high poly modling while not choking the pc with millions of polys on display. Plus curves are much nicer and easy to create using splines.

I was watching this Youtube video and couldn't figure out why my version kept capping the top and not his until rewinding and really following step by step.

Turns out I started with a circle spline while he started with an Ngon. That was all that I needed to do..

My question now is why?? Because of the extra vertices?