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Re: Software for a Student

Postby MK19 » August 25th, 2017, 3:12 pm


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The sub-D in F360 can convert to perfect nurbs surfaces which can be thickened etc though? If you use sub-D in Modo then you can't?

I am mostly annoyed that DS didn't buy T-Splines when they had the chance and rather than buy Power Surfacing and implement it they bought out an entirely new CAD package which noone is switching to. DS have shown they really don't care about their user base despite its size.

Re: Software for a Student

Postby Mrog » August 25th, 2017, 3:47 pm


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Well, yes, you can convert subDs to Nurbs in Fusion... but so can T-Spline for Rhino, or Inventor, any other incarnation of T-spline and even Maya can convert entire polygon objects to nurbs. Doesn't even Modo have some plug in to do that?

The advantage of Fusion is of course that you can have the conversion within the modelling process in the timeline and can always go back to your subD and make changes after the fact.
But what you also need to be aware of is that converted SubDs are not "clean" or "perfect" at all and quite the opposite of single span Class A modelling. The math of these surfaces is REALLY heavy. Yes, you can thicken them, etc. But it sounds much more useful than it is in reality cause they are so friggin overdefined and complicated that they break at every chance they get when you start building upon them and do things that go beyond a simple thicken of the surface. The SubDs can be a quick solution and sometimes are the easiest way out of a problem, but they are usually always the least elegant solution.

I really like the idea of what Fusion is trying to do with SubDs/T-Splines... but it is just not really finished and useful yet and almost creates as many problems as it solves, from a technical standpoint.

Re: Software for a Student

Postby cadjunkie » August 25th, 2017, 7:44 pm


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MK19 wrote:The sub-D in F360 can convert to perfect nurbs surfaces which can be thickened etc though? If you use sub-D in Modo then you can't?

I am mostly annoyed that DS didn't buy T-Splines when they had the chance and rather than buy Power Surfacing and implement it they bought out an entirely new CAD package which noone is switching to. DS have shown they really don't care about their user base despite its size.


There is a thicken command in Modo or you can pick geometry and offset the surface and then bridge or loft between them. Just as an aside you don't "have to" convert to NURBS to take something to be manufactured you can totally go direct to CNC, 3DP...etc.

Whom are you speaking of when you say DS bought another CAD package?

Re: Software for a Student

Postby cadjunkie » August 25th, 2017, 7:54 pm


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Mrog wrote:Doesn't even Modo have some plug in to do that?


The plug in is called Power SubD and honestly there's nothing else quite like it in industry in terms of pre-defining edges on a SubD model so that when converted to NURBS you can pick said edges and continue and CAD operations required.


[/quote]But what you also need to be aware of is that converted SubDs are not "clean" or "perfect" at all and quite the opposite of single span Class A modelling. The math of these surfaces is REALLY heavy. Yes, you can thicken them, etc. But it sounds much more useful than it is in reality cause they are so friggin overdefined and complicated that they break at every chance they get when you start building upon them and do things that go beyond a simple thicken of the surface. The SubDs can be a quick solution and sometimes are the easiest way out of a problem, but they are usually always the least elegant solution..[/quote]

If at all possible to show some examples of SubD that you'd consider not clean or perfect. I'm not necessarily disputing what you've experience just saying that there are possible ways to have bad NURBS geometry for a whole host of reasons. There are a fair amount of car companies using zBrush, Modo...etc as part of their design process. Not saying it's the end geometry used but this notion of "class A" being this be all end all is also kind of urban myth that people throw around with really thinking about what's really behind it. This could mean it was done in Rhino, SW, IV...etc. And when you say that SubD's are heavy, one that that you can do with mesh geometry that NURBS can't is actually decimate and reduce the heaviness. With NURBS you really can't do this.... you can try to rebuild it, yes, but that's about it. It'd be great if there were a shrink wrap feature for NURBS surfaces but alas....:(
Last edited by cadjunkie on August 26th, 2017, 6:30 am, edited 1 time in total.

Re: Software for a Student

Postby Mrog » August 26th, 2017, 8:36 am


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cadjunkie wrote:
If at all possible to show some examples of SubD that you'd consider not clean or perfect. I'm not necessarily disputing what you've experience just saying that there are possible ways to have bad NURBS geometry for a whole host of reasons. There are a fair amount of car companies using zBrush, Modo...etc as part of their design process. Not saying it's the end geometry used but this notion of "class A" being this be all end all is also kind of urban myth that people throw around with really thinking about what's really behind it. This could mean it was done in Rhino, SW, IV...etc. And when you say that SubD's are heavy, one that that you can do with mesh geometry that NURBS can't is actually decimate and reduce the heaviness. With NURBS you really can't do this.... you can try to rebuild it, yes, but that's about it. It'd be great if there were a shrink wrap feature for NURBS surfaces but alas....:(


I think you got me wrong, the SubDs themselves are mathetacially as clean, simple and smooth as it gets. It is really hard to mess up SubDs. It is the CONVERSION to NURBS that really f**ks things up. Converted SubDs are simply NASTY. Not only are they really heavy NURBS, also they are not able to maintain the perfect curvature of the poly mesh. Converted SubDs tend to "pinch" on starpoints. Even if the polysurface is absolutely pristine in Blender or Modo or whatever, once you convert it the curvature will do funny things. T-Splines are good to get you to where you want to be by 90% to visually ok data that is good for some prototyping. When you get into the nitty gritty surface developement it simply doesn't offer the necessary control over surface curvature and produces way way overdefined NURBS. And when I say Class A I mean single span. And converted meshes usually have a thousand spans. Think of it of converting a pixel image (that's the mesh) to a vector graphic (that's NURBS). The output might look ok, but it is usually overdefined beyond usability.

And yes, car companies use it for concept cars and prototyping because poly modelling is friggin fast. But first they usually stay exclusively in polys and don't convert, so they avoid all the curvature problems and second for an actual production car the data is useless and they will rebuild it single span... because the final precise control over curvature isn't there.

Re: Software for a Student

Postby cadjunkie » August 26th, 2017, 10:22 am


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Power SubD Export.jpg
@Mrog: Got cha....though I think there's a bit of some faulty footing you're on with regards to data translation. If I bring said "light weight" NURBS into say Modo or zBrush then you are going to see that the same "heaviness" found in importing the data in. This is not what happens when going back and forth as a raster to vector. They're all just different mathematical equations to represent what we see on the screen. There are advantages to being in both data sets to achieve certain intended outputs. Also lets not kid ourselves into think that NURBS can't get heavy just on their own. Having a range of features can still create a heavy data set that cause long rebuild times...etc.

Check the below screen shot that shows how a model can be set up for conversion when converting from SubD to NURBS. As "machines" start to take input from a wider range of sources there will be less need to have to convert to NURBS. I've CNC'ed from a mesh and it works fine but it can be production process dependent...

Power SubD Export.jpg

Re: Software for a Student

Postby MK19 » August 26th, 2017, 10:42 am


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Mrog wrote:Well, yes, you can convert subDs to Nurbs in Fusion... but so can T-Spline for Rhino, or Inventor, any other incarnation of T-spline and even Maya can convert entire polygon objects to nurbs. Doesn't even Modo have some plug in to do that?

Yes but for Rhino it is the company which Autodesk bought and they are no longer going to support T-splines. They are trying to kill it off to force people to switch to F360. I have seen examples of it done in Maya and would like to play with it but it would be yet another package to learn.

cadjunkie wrote:Whom are you speaking of when you say DS bought another CAD package?

Sorry, brought out. I mean SW ID.

Re: Software for a Student

Postby Mrog » August 26th, 2017, 10:51 am


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cadjunkie wrote:
Power SubD Export.jpg
@Mrog: Got cha....though I think there's a bit of some faulty footing you're on with regards to data translation. If I bring said "light weight" NURBS into say Modo or zBrush then you are going to see that the same "heaviness" found in importing the data in. This is not what happens when going back and forth as a raster to vector. They're all just different mathematical equations to represent what we see on the screen. There are advantages to being in both data sets to achieve certain intended outputs. Also lets not kid ourselves into think that NURBS can't get heavy just on their own. Having a range of features can still create a heavy data set that cause long rebuild times...etc.

Check the below screen shot that shows how a model can be set up for conversion when converting from SubD to NURBS. As "machines" start to take input from a wider range of sources there will be less need to have to convert to NURBS. I've CNC'ed from a mesh and it works fine but it can be production process dependent...

Power SubD Export.jpg


Yes to everything you say. My critique of the "heaviness" you get from converting even simple SubDs to NURBS is that especially Fusion 360 more or less encourages a workflow like that... which is a nice idea in theory because SubDs are great, but in practice they result in rather unwieldy NURBS that sooner or later always destroy the parametricness of the model or cause trouble with tolerances or a million other things that can go wrong because of overdefined data. What I am trying to say is that T-Splines is hella useful but it is not the end all be all to all modelling pains like Fusion pretends it is. Because currently the deep T-Spline integration is actually the only thing Fusion has going for itself. When it comes to pure parametric modelling solidworks is quite a bit better than Fusion and when it comes to the surfacing things like Rhino are at an entirely different league. In the end designers won't get around learning surfacing, parametric modelling and polymodelling. There is not one that can replace the other.
Which brings us full circle to the comment that learning Rhino is useless ;) It is not, there are so many things that are nearly impossible or really really hard to do with parametric modelling... and vice versa.

Re: Software for a Student

Postby MK19 » August 27th, 2017, 7:04 am


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Mrog wrote:
Which brings us full circle to the comment that learning Rhino is useless.

Sorry, that wasn't my point. I didn't give as much context as I intended - I mean in a 3 year degree (extremely limited time period really) learning Rhino is not worthy over properly getting a grip with SolidWorks in my honest opinion. Advanced surfacing is something which is beyond the scope of a 3 year degree for the majority of students and basic surfacing is as quick and easy in SolidWorks really.

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