Mobius Strip in SW

[Alin]

A few of us started a discussion about the limitation of SW in creating a Mobius Strip as a surface body. Long story short, we failed to create one, even when we used multiple faces.



The original conversation is there https://r1132100503382-eu1-3dswym.3dexp ... m0sahqpjeA, but I know that more experts are here.

What is your take?

[bnemec]

I don't really understand all the details or the proper definition of a Mobius Strip. It sounds like the requirement of being a continuous surface rather than a solid was added for this discussion. If we trace a solid body Mobius the trace would go around it twice to get back to the starting point. The solid body has a single continuous surface that goes around the body twice. My argument is that going around the Mobius once is not a full loop because the trace is on the opposite side at that point, need to go around again to get back to the starting point on the same side. This applies even if it were a surface.

I imagine the solid with edge faces removed to get the surface. It looks like two surfaces, but there's only one as that is the path that the object would take as it makes a full loop. The normal vector of that surface never flips, needing to flip the normal vector indicates that the trace has not gone all the way around, only half way. One could argue you're trying to do a half-Mobius Strip. As the thickness of the body goes to zero we still have one surface but to reach the limit of t->0 the surface would self intersect.

This is starting to feel much more like a ZTG discussion in disguise.

I get it you were trying to use both sides of a single surface, but I didn't understand any definition of a Mobius Strip to be zero thickness.

I wound up with this model attempt, I cannot find a blue line in the loop as you mentioned in the video, all four are black. But Checker still says there's one open surface.

[Frederick_Law]

I don't really understand all the details or the proper definition of a Mobius Strip.

Outside surface became inside.

[bnemec]

Outside surface became inside.

Right.

That was my layman's understanding of the concept. I'm used to things going over my head so I assumed there's more to it than that.

[Frederick_Law]

Let's give you a headache:
https://en.wikipedia.org/wiki/Klein_bottle

Maybe this will help:


Damn YouTube:

[bnemec]

Let's give you a headache:
https://en.wikipedia.org/wiki/Klein_bottle

Maybe this will help:


Damn YouTube:

Oh the irony of that video on you tube and it being linked to in a forum thread.

[Arthur NY]

@Alin

Not that hard.... Here's a model done in Solidworks 2001.....Yes forgot to add that these were done by Paul Salvador.

moe-figure-8.SLDPRT

(98 KiB) Downloaded 231 times

moe-figure-2-surfs.SLDPRT

(101.5 KiB) Downloaded 219 times

moe.SLDPRT

(52 KiB) Downloaded 224 times

[Alin]

@Alin

Not that hard.... Here's a model done in Solidworks 2001.....

moe-figure-8.SLDPRT

moe-figure-2-surfs.SLDPRT

moe.SLDPRT

Cool. I opened all three files.

1. Moe is not a surface body. As you could see in my video, I acknowledged that a solid body can be created (8 faces).
Also, Moe is not a Mobius strip. There is a 360 degree twist instead of 180.

2. Moe-figure 2-surfs is a collection of two surface bodies. If you try to knit them you still have an open edge.

This is what we are brainstorming -> is there a was to have a closed surface body (even if it has multiple faces) that resembles a Mobius strip?

3. Moe-figure-8 is not a Mobius strip (it has 2 sides)

[Alin]

I wound up with this model attempt, I cannot find a blue line in the loop as you mentioned in the video, all four are black. But Checker still says there's one open surface.

image.png

Could you please upload the SW file?

[josh]

Could you please upload the SW file?

No need. It's just a 3D mobius with its face offset zero to create a single surface with two 180 degree twists. No longer a mobius.

[matt]

Paul Salvador did this a couple decades ago....

http://www.zxys.com/swparts/

[DennisD]

Paul Salvador did this a couple decades ago....

http://www.zxys.com/swparts/

Among other (impressive) things.

[mattpeneguy]

Paul Salvador did this a couple decades ago....

http://www.zxys.com/swparts/

I think those files were listed above by @Arthur NY.

[Alin]

I think those files were listed above by @Arthur NY.

... and none of them satisfy the requirements I stated.

[bnemec]

Could you please upload the SW file?

I didn't save it. Nothing novel, as stated by Josh the screen shot is just a loop with a 360 deg twist.

Only thing different is instead of rotated sweep I used the flex (twist) feature to get the 180 deg twist.

First I extruded a surface and twisted that, then loft surface to close the gap and had blue edge, indicating open surface.

Second I extruded a thin feature and twisted that 180, lofted between the two faces to close the gap. Did offset surface half the thickness and confirmed still open surface with blue edge.

Then I strayed into theoretical over-my-head land of zero thickness Mobius Strip. If we go back to grade school with scissors and glue, take a piece of construction paper that is blue on one side and green on the other and make a Mobius with that. If we pretend the paper has zero thickness then there is one face and one edge. I would argue that the physical surface is not a continuous surface, there’s an inherent discontinuity at the point where we glue them together; indicated by sudden shift from blue to green. Another way of saying what was mentioned in Alin’s video that the normal vector of the face flips. Point is the Mobius Strip cannot be a continuous closed surface in real life, let alone in a model. Alternatively, the model is accurately replicating the physical, there’s a break in continuity where the loop closes.

Now back to the screen shot, as Josh stated, that is not a Mobius Strip, it’s just a loop with 360 degree twist. But if we reduced the thickness of the solid that loop came from down to zero, that surface would become a Mobius again as it converged on itself. That’s where I got off the train because I didn’t understand was I was thinking about.

[Alin]

Thanks to all for the suggestions. For me, the fact that a twisted face cannot be knitted at both sides to a surface body is very interesting.

So, no closed continuous strip of knitted faces can be created in SW if there is a half-twist anywhere in this "chain" of faces.

[mattpeneguy]

... and none of them satisfy the requirements I stated.

You want people to post files and meet the requirements?...You need to lower your expectations...

[DennisD]

You want people to post files and meet the requirements?...You need to lower your expectations...

Excuse me, @mattpeneguy, but Alin posted this first on the 3DSWAMP. THEN he posted it here to get a better intellectual discussion and better efforts.

[Krzysztof Szpakowski]

Hello everyone.
Nice to see/read. Also Reptilians (hi Dan) ;-)
Alin, I see you're not giving up on the Mobius strip theme. As you wrote, unfortunately, the reversal of the normal during the half-turn prevents such surface topology. Bnemec, You're right, you don't have a blue seam line, but it's not a Mobius strip. You have a half twist twice, which results in a full rotation of the surface and proper stitching.
Alin. I have an idea for the next topic. How about a perpetual motion machine? :-D

K

As a joke, I'm attaching a solid Mobius strip bounded by one surface.

mobius2.SLDPRT

(288.5 KiB) Downloaded 174 times

[Frederick_Law]

Second I extruded a thin feature and twisted that 180, lofted between the two faces to close the gap. Did offset surface half the thickness and confirmed still open surface with blue edge.

That's 1 Pi Mobius.

a loop with 360 degree twist

2 Pi, not Mobius.

3 Pi, Mobius.

We need Mobius slot car tracks.
Alin, next SLUGME project

Is any roller coaster track Mobius?

[Krzysztof Szpakowski]

Hi Frederick.
Mobius strip has one more interesting property. Cutting it along we get... no... no... not two strips but one! Only narrower and longer,

[Arthur NY]

More than anything else this just goes to show that most software's within the CAD industry have NOT progressed in over 10 years. No new major features to create designs with. Extrude, Revolve, Loft, Sweep and Boundary have been the major tools and as a whole DDS major focus has been moving to 3D ESP.....errrrrr 3D EXP.....oooops I mean 3D Widget Wizard Online!!!

There was a time when I use to look forward to seeing what's new coming in the next version of Solidworks. And even if we were to say that DDS has made it so that the software is more stable.....etc, the amount of broken functionality that hasn't been addressed in over 15 years is mind boggling. The little bells and whistles that have been added over the years are nice to have but no new real geometry creation tools is just plain sad.

[gristle]

I tried this with two surfaces in SW. One edge will knit, the other won't. Dump the geometry into Rhino and it can join one edge but when trying to join the other it gives an 'inconsistent normals' error. Honestly, this is unsurprising. Displaying normals illustrates the issue clearly.

[DennisD]

That's 1 Pi Mobius.



2 Pi, not Mobius.

3 Pi, Mobius.

We need Mobius slot car tracks.
Alin, next SLUGME project

Is any roller coaster track Mobius?

And then replace the roundabouts with this!

[SPerman]

As I am recovering from my latest crash, all I can think is that I just want software that can draw euclidean geometry reliably. My need for modelling mobius strips is rather low.

[DennisD]

As I am recovering from my latest crash, all I can think is that I just want software that can draw euclidean geometry reliably. My need for modelling mobius strips is rather low.

But here's the thing. Once you get onto the topic of Mobius strips you can never end it.

[Krzysztof Szpakowski]

but no new real geometry creation tools is just plain sad.

I don't know what you mean by "real" geometry. I promise you that I modeled a lot of real geometry in my old SW2012. And despite the lack of several tools that have appeared since then (e.g. offset surface boundaries, cone round), I have never had "real geometry" kill that old SW version or me ;-). And I write this not as a supporter satisfied with the software development and policy of DS. Those who know me can confirm this. But the impossibility of designing true geometry? Believe me, SW has great potential. Most limitations lie within us.

PS
Here you have as a "gift" a Klein bottle which is very easy to model in SW.

klein.SLDPRT

(469.5 KiB) Downloaded 174 times

[Krzysztof Szpakowski]

And then replace the roundabouts with this!

szczer.jpg (4.26 KiB) Viewed 23175 times

[Arthur NY]

@Krzysztof Szpakowski

So let me break it down for you to make it easier to follow.... Geometry Creation Features/Tools like Extrude, Revolve, Loft, Sweep. There have been NO new tools really added of any significant in over a decade. If you look at SW 2002 vs Solidworks 2012 there were huge jumps and differences in the tools and features added. I couldn't go back from 2012 to 2002 and still get the same work done. Contrast Solidworks 2012 to Solidworks 2022 and there's very little difference. Meaning I could go back to 2012 and still be just fine.

This isn't a knock against Solidworks only this is the CAD software industry as a whole.

[Arthur NY]

I tried this with two surfaces in SW. One edge will knit, the other won't. Dump the geometry into Rhino and it can join one edge but when trying to join the other it gives an 'inconsistent normals' error. Honestly, this is unsurprising. Displaying normals illustrates the issue clearly.

You've hit the nail on the head. Am so use to not have to deal with normals in Solidworks because the Parasolid Kernal doesn't work that way. Which explains why it can be done as a solid and not a surface.

[gristle]

You've hit the nail on the head. Am so use to not have to deal with normals in Solidworks because the Parasolid Kernal doesn't work that way. Which explains why it can be done as a solid and not a surface.

In my Wildfire days, I did use the 'flip normal' feature a few times. It was quite handy for fixing merges (trims) where the wrong side was being trimmed. If SW had flip normal, it might help with those occasions where trims fail or when the wrong side is trimmed. Being able to display the surface normal direction would be handy as well.

One thing added since 2012 that I use all the time is style splines.

[Alin]

@Krzysztof Szpakowski

So let me break it down for you to make it easier to follow.... Geometry Creation Features/Tools like Extrude, Revolve, Loft, Sweep. There have been NO new tools really added of any significant in over a decade. If you look at SW 2002 vs Solidworks 2012 there were huge jumps and differences in the tools and features added. I couldn't go back from 2012 to 2002 and still get the same work done. Contrast Solidworks 2012 to Solidworks 2022 and there's very little difference. Meaning I could go back to 2012 and still be just fine.

This isn't a knock against Solidworks only this is the CAD software industry as a whole.

If we were to look with a magnifying glass, we can find a few gems in sketching and part modeling like the Intersect tool, wrap and unwrap anything on anything, style spline, offset surface that works, more powerful patterns, silhouette, defeature silhouette, sketch symmetry about faces and planes, C3 (torsion) relation, thread, scale tool, advanced fillets and chamfers, and a few more.
For assemblies there is so much more.

[Arthur NY]

@Alin I've said this before.... I'm not the normal run of the mill Solidworks user. What you're point out in no way shape or form comes close to what I'm talking about. It's ok.... you can just agree with what I said and call it a day. I realize that it's hard for AE's to say as such because you have to toe the line, but at least just be realistic.

Yes all of these very little additions help along the way but I'll rebut you and say that patterns have not gotten better in terms of going over a certain quantity. You still take a huge hit in performance and that's more than 20 years old.

Here are a few VERY outstanding items that have still yet to be addressed.

"Move/Body" feature... that you can't translate AND rotate in the same operation is so 1995.

Splines:
- The base Spine's preview behavior changed around 2008-ish or so but what the new one is sucks big time.
- Adding C3 is kludge at best. The rules are not consistent in just the 2D solver let alone the 3D Sketcher. it's gotten better since it was first added but it is still a far cry from what it should be.

Scale Tool: Maybe it's just me here but the Scale Feature still works the same is another one that is so 1995!!! It's been in the software since the beginning. BUT that you still can't access the numbers outside of editing this feature is MIND BLOWING!!!! Just boggles the mind... and no don't mention that it can go into a config table...etc. The scaling numbers should show on screen like the majority of the other features.

Intersect Tool: Basically a combination of tools that really already existed in other areas of the software. Golf clap for that but it's not game changing by any means.

offset surface that works: That it didn't work as prescribed and now that it does and we users should be grateful for that? How is that a good thing?

Back on topic..... Since Solidworks can't show normals here is a screen shot that explains 100% why, as a surface, the software can't be one knits surface. This is screeshot from Rhino3D that shows the one face in purple being the negative side of the surface which is what the software is not able to resolve as a single knit surface. If there's nothing else that I do like about Solidworks is that it does what we tell it to do, nothing more nothing less which is what makes it pretty rock solid overall.

[Alin]

@Alin I've said this before.... I'm not the normal run of the mill Solidworks user. What you're point out in no way shape or form comes close to what I'm talking about. It's ok.... you can just agree with what I said and call it a day. I realize that it's hard for AE's to say as such because you have to toe the line, but at least just be realistic.

If we were to list all the things that could be improved, the list would be measured in miles. I started cataloging all the areas where the developers stopped before fully completing their job and I would welcome if more users like you would find the time to add more items to this list.

https://forum.solidworks.com/thread/238018

If you want a new list to be hosted on @matt 's site, that would be fine. Of course, only if you and other power-users would be interested in that.

[Krzysztof Szpakowski]

@Krzysztof Szpakowski

So let me break it down for you to make it easier to follow.... Geometry Creation Features/Tools like Extrude, Revolve, Loft, Sweep. There have been NO new tools really added of any significant in over a decade. If you look at SW 2002 vs Solidworks 2012 there were huge jumps and differences in the tools and features added. I couldn't go back from 2012 to 2002 and still get the same work done. Contrast Solidworks 2012 to Solidworks 2022 and there's very little difference. Meaning I could go back to 2012 and still be just fine.

This isn't a knock against Solidworks only this is the CAD software industry as a whole.

I suspect that you did not work with early versions of SW, which, for example, were not suitable for my application due to limitations in surface modeling. And it was between 1995 and 2002 that much more functionality was added to modeling tools than later. I don't know what new "real geometry" modeling tools you expect? Someone once asked a question on an old forum: How to model a rhinoceros in SW? If you need these types of tools, such as "Giraffe neck shape" "Bugatti Vayron hood surface", you won't get them.

[Glenn Schroeder]

If we were to list all the things that could be improved, the list would be measured in miles. I started cataloging all the areas where the developers stopped before fully completing their job and I would welcome if more users like you would find the time to add more items to this list.

https://forum.solidworks.com/thread/238018

If you want a new list to be hosted on @matt 's site, that would be fine. Of course, only if you and other power-users would be interested in that.

Most of the links in that discussion don't show up for me, and the ones that do don't go anywhere useful.

[Alin]

Most of the links in that discussion don't show up for me, and the ones that do don't go anywhere useful.

Yup. Same.

[Glenn Schroeder]

Yup. Same.

Also, for the last week or so I've been getting notices that someone has replied to that thread, but when I go there I never see anything other than the one reply from @Frederick_Law.

[Arthur NY]

If we were to list all the things that could be improved, the list would be measured in miles. I started cataloging all the areas where the developers stopped before fully completing their job and I would welcome if more users like you would find the time to add more items to this list.

https://forum.solidworks.com/thread/238018

If you want a new list to be hosted on @matt 's site, that would be fine. Of course, only if you and other power-users would be interested in that.

I've been Alpha/beta testing for about 20 years with SW HQ direct. They don't listen because their in a bubble. Mark Biasotti and I would have very long conversations about this and in the end a lot of the reasons why SW didn't give anything new for a long time was because DDS was trying to get users to upgrade to Catia. It never worked because of the price differentials. In the end what they list as "user driven" additions to the software is a bunch of smoke and mirrors.

[bnemec]

Also, for the last week or so I've been getting notices that someone has replied to that thread, but when I go there I never see anything other than the one reply from @Frederick_Law.

Curiosity got the best of me and I went and logged in.
Maybe Alin can update the subject to "The missing 5% functionality - 5% of All of the Chapters"

[Arthur NY]

I suspect that you did not work with early versions of SW, which, for example, were not suitable for my application due to limitations in surface modeling. And it was between 1995 and 2002 that much more functionality was added to modeling tools than later. I don't know what new "real geometry" modeling tools you expect? Someone once asked a question on an old forum: How to model a rhinoceros in SW? If you need these types of tools, such as "Giraffe neck shape" "Bugatti Vayron hood surface", you won't get them.

I've been 3D modeling since the early '90's. Using Solidworks since '97. Using anything from CAD Key, Alias Wavefront, SDRC and Pro/E..... I am quite familiar with everything the software is capable of. I can also say that even with 2000 version there were some crude surfacing capabilities if you knew what you were doing. Point and case these models from Mike J Wilson were made in Solidworks 2001.... Scooby Doo, Speed Racer Mach 5 Car...etc.

https://www.mikejwilson.com/otw.html

Also Paul Salvador's website is filled with TONS of surfacing examples from very early on. I know because it was one of the first Solidworks model websites that I learned a lot from.

http://www.zxys.com/swparts/

Was Soliworks making Class A surfacing that I could get in Alias, no, definitely not. And even to this day is still quite lack luster in so many ways when it comes specifically to surface modeling. None of this negates the overall aspect that it's a sad day on the CAD software side of things in general.

[Frederick_Law]

Also, for the last week or so I've been getting notices that someone has replied to that thread, but when I go there I never see anything other than the one reply from @Frederick_Law.

Oh, good. I thought they blocked me

PS, I replied and it instantly went to the bottom of the SWYMP

[Glenn Schroeder]

. . . In the end what they list as "user driven" additions to the software is a bunch of smoke and mirrors.

I've complained about the things DS does often enough, and likely will again, but I don't agree with that statement. There have been a number of changes to the software in the 14 years I've been using it that were user driven. There have even been a few that I specifically asked for, usually through submitting ideas for SW World Top 10 (at least two showed up in SW2023; see viewtopic.php?t=2789).

Edit: Also, see viewtopic.php?p=31123#p31123

[Arthur NY]

I've complained about the things DS does often enough, and likely will again, but I don't agree with that statement. There have been a number of changes to the software in the 14 years I've been using it that were user driven. There have even been a few that I specifically asked for, usually through submitting ideas for SW World Top 10 (at least two showed up in SW2023; see viewtopic.php?t=2789).

Edit: Also, see viewtopic.php?p=31123#p31123

That part of the post is some what tongue and cheek. Sure there are things that have been added into the software that has been user requested. What I can say is that there are a lot of things that are actually internally posted as things for them to add into the software and then use a request as reason to bring it to the front burner.

Also, at the core, when the software was first launched it was "For Engineers .... By Engineers" and now a days it's more like software that's more for management and C-suite level people. The PDM and PLM aspects, while important, and do trickle down to the engineers it not helpful in the day to day in terms of making models.

[mp3-250]

@Arthur NY

if you have 100 engineers working with the same data pdm is very important.
problem is SW is not even fixing the basic tools and functionalities of SW PDM (which was an acquisition not internally developed), so I do not ubderstand where the perception of resources going to PDM came from.
it is an incomplete tool acquired from conisio, so like the cad and sketcher engine (licensed from siemens) SW did not develop from them scratch to begin with.

[Arthur NY]

@Arthur NY

if you have 100 engineers working with the same data pdm is very important.
problem is SW is not even fixing the basic tools and functionalities of SW PDM (which was an acquisition not internally developed), so I do not ubderstand where the perception of resources going to PDM came from.
it is an incomplete tool acquired from conisio, so like the cad and sketcher engine (licensed from siemens) SW did not develop from them scratch to begin with.

Am well aware of both their PDM and Sketch solver. I do understand the reason for PDM for a team of engineers. But that has nothing to do with the base core functionality of the Features/Tools not evolving.

Part of what you're seeing is the tapering off of anything Solidworks and the slow, death by 1000 papercuts, move to 3D Experience Platform. This is what I mean by focus on PLM, PDM...etc. If you look at the "What's New" PDF over the course of the past 10 - 15 years you'll see that it been a slow and steady creep of this lack of adding new features.

[mp3-250]

@Arthur NY
my point is they should focus on making SW works.
Adding new functionalities keeping the rest broken is not good.
At the current state only a fraction of SW tools are reliable to be used in a medium sized company like us, the rest is going to bite you back and,make you rework a lot of data or slowing down the product development.

[zxys001]

Cool. I opened all three files.

1. Moe is not a surface body. As you could see in my video, I acknowledged that a solid body can be created (8 faces).
Also, Moe is not a Mobius strip. There is a 360 degree twist instead of 180.
image.png

2. Moe-figure 2-surfs is a collection of two surface bodies. If you try to knit them you still have an open edge.
image.png
This is what we are brainstorming -> is there a was to have a closed surface body (even if it has multiple faces) that resembles a Mobius strip?

3. Moe-figure-8 is not a Mobius strip (it has 2 sides)
image.png

Yeah, only one there but with the split (or a fail) we all were trying different ways and these were a few I had played with 22yrs ago.

[zxys001]

I don't know what you mean by "real" geometry. I promise you that I modeled a lot of real geometry in my old SW2012. And despite the lack of several tools that have appeared since then (e.g. offset surface boundaries, cone round), I have never had "real geometry" kill that old SW version or me ;-). And I write this not as a supporter satisfied with the software development and policy of DS. Those who know me can confirm this. But the impossibility of designing true geometry? Believe me, SW has great potential. Most limitations lie within us.

PS
Here you have as a "gift" a Klein bottle which is very easy to model in SW.

kleib.png

klein3.effectsResult.png

klein.SLDPRT

Unlimited Wine!?

[Krzysztof Szpakowski]

Unlimited Wine!?

Thank you o Great Lord Klein