Visible crease when creating surface from sweep, no crease when swept from Rhino  1-20  21-25

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 From:  niko (NICKP100)
3473.1 
That little cutout(where it joins with the big surface) produces a visible crease in the rhino viewport when imported in, but when it is actually swept inside Rhino(using the same method of course) the crease is not visible.
Any ideas?

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 From:  Michael Gibson
3473.2 In reply to 3473.1 
Hi Niko, could you please point out which things you are using as rails and which things as profiles for the sweep, and also what parameters you are using in Rhino?

But one thing to be aware of is that it is pretty normal to have creases between things if you build them in individual chunks, see here for a description:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.19


If you want to have smooth things, you're usually better off building them as larger surfaces instead of as cut up strips.

- Michael
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 From:  Michael Gibson
3473.3 In reply to 3473.1 
Hi niko, also this kind of thing here tends to be kind of bad for sweep in both MoI and Rhino:




Your profile curve there stretches out quite a bit and is tangent to where it touches the rail, which is very unlike the other profile curve on the other side.

This creates a surface with control points really kind of compressed in that corner area:



This point here is actually the corner point of the NURBS surface point grid:



It's very easy for such things to have bad surface qualities in that area, with the surface actually being bunched or folded back over on top of itself right in those corner areas.

You may want to do something like put in a surface blend here and then trim it to make it rounded at the end rather than trying to sweep in this way.

- Michael

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 From:  Michael Gibson
3473.4 In reply to 3473.1 
Hi niko, or maybe something more like this:

Sweep an extended shape:



Then trim off the end:



That then gives a much more regular surface structure which looks like this:




That will tend to avoid bunching or self-overlapping in the surface.

- Michael

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 From:  Michael Gibson
3473.5 In reply to 3473.1 
Hi niko, so back more on your original question, one thing about Sweep is there is not a single "canonical" way to do sweeping, unlike something like Extrude or Revolve.

Sweep is a much more complex process that involves a kind of repeated refinement, and it's not likely that you're going to see the exact same result between 2 different programs doing the sweeping.

If you look at the surface control points, you can see that Rhino happened to generate a surface with more control points in it along what I think was your rails direction. In this particular case, that happens to make a shape that is slightly less creased to the other surface but that is more or less just a matter of luck.

- Michael
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 From:  niko (NICKP100)
3473.6 
Ok understood. I fixed the cutout with the trim method.
I still have the same problem though even though I fixed the cutout.
View both in Rhino and you'll see the difference. (The blanks in the MOI file are created with the network command while the U-shape is a blend). One was recreated in Rhino while the other is a direct import from MOI.
Thanks Michael

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 From:  Michael Gibson
3473.7 In reply to 3473.6 
Hi Niko, well like I mentioned before, if you use a surfacing command that only works off of curves (rather than being particularly designed to work off of surface edges and adapt to surface continuity like blend), then it is going to be normal for you to see creases between things if you build them in a piece by piece manner.

In order to eliminate creases you have to do some extra steps, something like cut some space between things and use Blend, or use Rhino's Match command to edit the surface.

That's going to happen in different cases in Rhino as well.


In the most recent files you posted, one thing to note is that your MoI file does not have surfaces joined together, that's going to cause different meshing between them and accentuate the division. So make sure to join surfaces together if you are going to compare the shading.


If I load your last posted files into Rhino, I get the Rhino one looking like this:




And the MoI one after joining looks like this:




There still seems to be a crease in the Rhino one, I think that you're right that it again happens to be by chance a couple of degrees less than the MoI one but I wouldn't consider that a really major difference.

Possibly MoI and Rhino use a slightly different method for rotating the profiles as they travel along the rails or something like that.

- Michael

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 From:  Michael Gibson
3473.8 In reply to 3473.6 
Hi niko, here's another shot of your last MoI model with just diffuse lighting only:



That crease that you're talking about is really pretty subtle.

That kind of thing is just a general problem when building surfaces in a kind of "patchwork" like manner like this.

One option is to use the Match command in Rhino to tune up surfaces built like this to have better continuity.

But if you're looking to make deformations in things and maintain super smoothness, you might want to look into a sub-d modeling toolset like TSplines instead of doing a NURBS patchwork.

- Michael
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 From:  niko (NICKP100)
3473.9 In reply to 3473.8 
Well maybe it's the way files get imported into Rhino, but after sweeping the previously blank areas there's definately an obvious very visible ugly crease in the MOI model(there's no curves there I used the surface edges). In Rhino I used a 2 rail sweep with the curvature option on and it came in super smooth. In MOI I picked the maintain tangent option to avoid creasing.
Check it out for yourself.
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 From:  niko (NICKP100)
3473.10 In reply to 3473.9 
I also get the same problem when I try to create a network.
I think it might be that Rhino creates a smoother result because both sweep and network give the option to maintain curvature where as MOI does not have that option.
I guess what I'm asking is if there's any plans to enhance these commands or if there's something else I'm missing.
I apologise if all this sounds like bitching but I love MOI so much that I hate co-working with Rhino to get the desired result
Thanks
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 From:  Michael Gibson
3473.11 In reply to 3473.9 
Hi niko, the "maintain tangent" option in MoI does not do the same kind of a thing as what you were thinking.

It does not adjust the tangent to adapt to a surface edge, instead it makes the sweep work by moving the profiles only in parallel planar slices instead of sliding them along the rails where they can potentially get twisted from their original orientations.

You also can only use it with some particular configurations, like when the profile curves are all on parallel planes to one another and share a common tangent direction on one side.

I probably should have called it something like "Position profiles along parallel planes" or something like that instead, but it was a bit difficult to describe.

See here for some illustrations and description of what that option in MoI actually does:

http://moi3d.com/forum/index.php?webtag=MOI&msg=2908.13
http://moi3d.com/forum/index.php?webtag=MOI&msg=2226.11


It's totally different than the continuity options that you were using in Rhino.


> In Rhino I used a 2 rail sweep with the curvature option on and
> it came in super smooth.

Maybe you were using different curves for the rails than I was? Or is that something new in Rhino v5 where you can adjust continuity for a profile curve instead of only along the rails?

But yeah if you are using the continuity options, that's something that MoI does not have yet, you currently need to use Rhino if you want to have continuity adjusted for Sweep or Network.

I do plan on working on adding those to MoI in the future.

- Michael
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 From:  steve (STEVE_HOME)
3473.12 In reply to 3473.10 
Hi niko,

I thought I would try to see what problem you are having. Looking at the current surface patching I am seeing problems where the patches are not G2. I have attempted to correct in MOI, but the more I attempt to correct the more rebuild is needed. It would probably be easier for me to start from beginning, however, I have attached where I got to, to see if this is closer to what you where wanting.
There is the slight problem of the far right edge, where some editing/trimming is still needed.


- Steve
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 From:  Michael Gibson
3473.13 In reply to 3473.9 
Hi niko, I guess one thing that confused me is I assumed in your original model that you used these as the rails:



and these ones as profiles:



But it seems you were using them the other way around.

- Michael

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 From:  niko (NICKP100)
3473.14 In reply to 3473.13 
Hey Michael
I actually used the trim method which you described.
The problem however was not with the original crease which in fact turned out to be pretty close to Rhino but with the creases made by the patches which were originally left empty in the shipMOI model I posted. There's two of them.
I guess after tinkering in Rhino I think I came to the premature conclusion that the problem lies with MOI not letting me adjust the refit tolerance. When I use more decimals I get the same problem in Rhino, whereas if I keep it at.001 or.01 it reshapes the patch to fit that tolerance and appears a lot less creased.
In Rhino this can be adjusted within the Network and sweep commands.
Is there anyways I can adjust this in MOI?
Your help is always appreciated
Thanks
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 From:  Michael Gibson
3473.15 In reply to 3473.14 
Hi niko,

> whereas if I keep it at.001 or.01 it reshapes the patch
> to fit that tolerance and appears a lot less creased.

That's just a matter of luck... To not have creasing you really need to use options specifically related to continuity, not really just random geometric side effects from a denser or lighter surface fitting that happens from a tolerance adjustment.


> In Rhino this can be adjusted within the Network
> and sweep commands.
> Is there anyways I can adjust this in MOI?

No, the tolerance is not adjustable in MoI.

But even if it was, it's not really the thing you would need for this case, you need some option to modify the generated surface to have continuity to the other existing surfaces, that is not something that is directly controlled by a fitting tolerance.

I do want to add continuity options in to MoI in the future, but for now you would need to use Rhino for trying to make this kind of curvature continuous patchwork skin.

But even then this type of "patch-by-patch" approach can be frustrating to do with NURBS, it is probably better to do with a sub-d modeling approach rather than with NURBS.

- Michael
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 From:  niko (NICKP100)
3473.16 In reply to 3473.15 
Everytime I can't do something in MOI it breaks my heart....seriously
hopefully we'll see the continuity options in V3, as I think that they're very important.
Continuity is not something that exists only in organic models...look at a car or a boat for example.
This patchwork method is sometimes inevitable in some models and to be honest I still find the NURBS method way faster. I managed to do this in MOI (with the help of Rhino of course) in a matter of no more than 5 minutes. Doing it in Modo would be a more trial and error thing.
If anybody can think of a method to get that result without leaving MOI Id be interested to know
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 From:  Michael Gibson
3473.17 In reply to 3473.16 
Hi niko, I certainly wish that MoI could have every single function in it all at the same time, but please keep in mind that with just 1 person working on it, it can take time to make progress particularly in more advanced or specialized modeling areas.

This kind of "stylized surface modeling with continuity" is kind of a finicky and advanced workflow that can often have difficulties even when all the tools are in place.

It basically uses techniques from the era when NURBS modeling was something done on an SGI workstation.

Long ago people used to model characters and such with the same kind of techniques, but that kind of workflow has been largely replaced by subdivision surfaces. That's why I have not focused on this particular area yet, it does not really play to the primary strongest areas of NURBS modeling which is actually more in solid modeling and booleans where designs are driven more by 2D profile curves rather than swooping around all over.

See these for some similar discussion on another recent thread:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3425.3
http://moi3d.com/forum/index.php?webtag=MOI&msg=3425.4
http://moi3d.com/forum/index.php?webtag=MOI&msg=3425.24


The primary focus for MoI early on is to make it really quick and easy to do simple models. The kind of stuff that you are talking about does not really fit into that category, it's just not an area that is fully fleshed out yet in MoI.

I do expect to make progress in it though!

In the meantime, there is no reason for it to "break your heart" ! :) You sometimes will need to export things to Rhino, do your thing over there, and then copy/paste back into MoI. Over time you will be required to do that less and less.

- Michael
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 From:  BurrMan
3473.18 In reply to 3473.16 
>>>>If anybody can think of a method to get that result without leaving MOI Id be interested to know>>>>

I wanted to look at this for some learning. Although Michael has probably given a proper workflow, this is how I would fix it in MoI.

I projected curves onto the seperated tounge surface then ran a loft and joined it back in. It seems to have cleaned up that one area a bit, but maybe I have produced other pitfalls I dont see. Feedback welcome.

I did notice that trying to loft it, was creating some funcky stuff up at the tip of the tongue, where I was trying to end it with the little "arc". I tried a few different methods, and it would create a joined surface, but not sure if something here is problematic later down the road for something else???

Anyway, just focused with tunnel vision on the one little area and removed the crease from the join.

EDITED: 19 Jun 2012 by BURRMAN

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 From:  niko (NICKP100)
3473.19 In reply to 3473.18 
Hey guys
Burrman, your results are similar to what I was getting.
Here's what your model looks like when rendered.



And here's what I was trying to do.Following Steve's advice I had to abandon the idea of doing2 sweeps or 2 network plus a blend at the U spot (because MOI currently lacks continuity options in both of these commands) and did 3 blends instead so that continuity is ensured.



You can check my model which I attached.
This brings me to my next request/question for Michael. In case (like in the attached file) the multi blended surface (which now has multiple edges on one end) has to be attached to another surface with a single edge,will it be possible to accomodate that in the V3 version of the blend command ?
I'm sure a multiple edge blend was requested but I'm not sure if a multiple edge to a single edge blend was.

Thanks STEVE and Michael and everybody else with your feedback

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 From:  BurrMan
3473.20 In reply to 3473.19 
Niko,
I didnt redo the U shape part, I only focused on the part you were pointing to at the top of the U where it crossed the surface.
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