Hi Roger, have you actually run into difficulty with a T-splines model that was just exported as a set of NURBS patches not being acceptable because it made a really large file or something?

I mean, that is actually the main focus of T-splines, to give a sub-d workflow but make a NURBS result...

Did you maybe get something like a client that considered the t-splines output to be unacceptable because it was different from the kind of structure that they were used to?


But yeah if you want to have a final output that is structured like a more typical CAD model, then building it in NURBS from the start would help get you that result... But also for really sculptured / non-2d-profile stuff it will mean operating with a more advanced (and difficult to use, and sometimes kind of headache inducing) kind of toolset instead of the simple solid modeling toolset.

The one you have here is actually not bad at all, but if you start to have broader pieces of the model that you're trying to surface in that way with multiple simultaneous transitions and branching type stuff, all while maintaining high continuity, that's when sub-d/t-splines starts to really become a lot more efficient.

- Michael

Hi Michael,

I haven't had any 'trouble' as such, but I have had issues where my sub-d models have had to be re-edited after conversion because, for example, a circle of a set diameter was very slightly out even though it looked fine by eye. Due to the stretchy nature of sub-d's it's extremely difficult to get cad-accurate results. Bearing in mind I mainly build models of bottles, which must be symmetrical for manufacture.
For example the indentation on the bottle above is perfectly circular in the MOI one but the sub-d one is slightly off due to the difficulty of faking a boolean cut across a curved surface.

Recently a client needed to edit the radii on the neck of an odd shaped bottle that I'd build in modo. He'd specified one size that later needed changing. Normally he could just tweak this himself in something like Spaceclaim, but because T-Splines had patched over all the radii, instead of retaining them, he had to send it back to me to regenerate. He wasn't too happy about it.

I still use t-splines though as it really is very clever. I often end up with a hybrid model that has a sub-d body and a cad neck. Having MOI handy makes that kind of thing very easy. Horses for courses I guess.

cheers
Roger

>You mean have solids and surfaces automatically drawn in different colors?

Yes, something like that. Are those color options you ment available in trial 1.0 version?

Thanks,

d3

Hi d3,

> Are those color options you ment available in trial 1.0 version?

No, they're part of the new stuff that's in MoI version 2.0 .

- Michael

Hi Roger, I see, thanks for explaining it more.

Yes definitely getting things that are exactly circular is a big problem with sub-d...

If it's an exact circular hole that you need, that's something that a hybrid approach could be good with, like use sub-d/t-splines to build the full shape, convert to NURBS and then cut the hole with NURBS.

But if it's more of your main body shape that needs to have some exact circular shape, I can see that's going to be more difficult in sub-d. Sub-d is kind of more oriented towards things that are going to be more melty all over and not really having a specific radius called out.

Bottles seem to be a pretty difficult case combining a lot of different shape types...

- Michael

Its been a while since I looked at MOI, so had a play.
I do not like trying to patch up surfaces in MOI, so made a quick rebuild of the bottle/cut outs (as close as possible, albeit quickly done). I can get a G1 blend, but a G2 would require some changes to the bottle surface/cutouts.

How is that cut done?


Thanks,

-d3-

>>How is that cut done?<<

Is that a question to my post/model?

>>>Is that a question to my post/model?<<<

Yes, it was. I was wondering, have you used boolean to make the cut?
Looks fine, no bad edges when checking in 3d printing software.


Thanks,

-d3-

OK Steve, How the hell did you do that!! It looks lovely. I can get that in Rhino using a 2 rail sweep with tangency but not in MOI. Also, such a super smooth indentation with one surface.
Share your secrets oh master! :-)

Roger

It's a very interesting Polygonal point structure to the bottle. Interested to know how the bottle was made in MoI. :o

Hi Burr,

> It's a very interesting Polygonal point structure to the bottle.

That's actually what an exact surface of revolution looks like.

When you have an untrimmed surface of revolution, when you turn on the points for it in MoI, you will get the points for an automatically rebuilt surface instead which is more friendly for point editing than the exact one that has fully multiple knots in it. If you edit the polygonal looking point structure, you'll see that if you pull points of that structure around it kind of splits into quadrant pieces rather than staying as a single totally smooth surface.

If a surface is trimmed though, that automatic rebuilding will not take place. In this case the surface is trimmed so that's why you see that squarish polygonal point structure.

If you untrim it by selecting all of its edges and pushing delete, then you'll see the rebuilt control points appear on it instead when you turn surface points on.

- Michael

Aha. Very intersting. Never noticed that before.
Thanks

Hi Roger,

Sorry, I did not keep the construction (I am in a bad habit of deleting construction (in MOI V1), I need to get used to the fact MOI now has layers)

The main body is revolved (I made a spline from the edge/shape of the bottle, then revolved) I then cut a circular hole into the neck, copied the edge of the hole, trimmed and made blend to lines set at the top of the cutout, then trimmed away the rest of the cutout. The cutout edges where then merged.

The lip is made by Network (to make it one surface).

Hi Steve,

Thanks for that. I'm not sure I entirely follow how you got from a circular hole to the final shape but I'm going to have another stab at this and see what happens. It's amazing how you've got no cut lines across your indent surfaces. Hmmmm..

Cheers,
Roger

Hi Roger,

I picked the various construction lines from your original model.

After making the revolve I extruded a circle (I created the circle from the orientation of the lip, size from the cutout) to intercept/trim the main body.



I then copied the edge of the cutout, trimmed that new curve and made blend to lines I had created from the top of the original cutout.




I then extruded the blend curves (+ a line connecting them) and trimmed the top of the cutout.




I then selected the edges of the cutout and merged them.


- Steve

Very interesting but I still don't get it.
I think this would be a great candidate for a tutorial video.
Thanks for sharing man, your input is greatly appreciated.

Ok, I have again very interesting question, is there someking of skin on bottle or why I dont see all edges,and curves, are they suppressed?

Hi d3,

> Ok, I have again very interesting question, is there someking
> of skin on bottle or why I dont see all edges,and curves, are
> they suppressed?

Nothing is hidden as far as I can tell...

Where exactly are you expecting to see additional curves or edges?

If you have surfaces that are built in smaller pieces and joined, then you will have more edges in a model. If you have a smaller number of surfaces each of which is larger in size then you will also have less edges in a model.

Are you maybe talking about an isocurve type display? Some programs draw additional extra extracted curves in the middle of surfaces as just another way to display them. But that's kind of an old remnant from the time when everything was only displayed in wireframe instead of shaded. MoI does not draw extra isocurves and instead just focuses on showing you the surface without extra clutter drawn on top of it. But the edges of all the trimming boundaries are shown in MoI unless you have decided to hide them yourself.

- Michael

Hi Steve, I'm interested in your method also. The more you can expound the better!!! The inset tab creation from there?

Thanks