Robert McNeel & Associates are in decline

If this discussion carries on someone should change the title …
who would want to do CAD without Grasshopper ? The future is bright.

T-Splines are like subdivision surfaces […], with the difference that you can insert geometry without changing the surface.

– Quoted from : http://www.tsplines.com/products/what-are-t-splines.html

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I think it was clearer to use somewhat other terms:

Mesh-based SubD modeling as used in Maya, Modo, Cinema4D, Blender… works with quad-meshes which can be represented in a very lose and boxy form or with millions of polygons, so that they may become very smooth (but still consist of facetted geometry).

Limit surface based SubD as used by Tsplines Clayoo, Catia, Siemens NX and other implementations inside CAD programs use the end-result of arbitrary many subdivisions and therefore have a perfect smooth geometry representation.

Mesh based Subdivision surfaces modelling takes place inside modelling applications which usually don’t offer any other way to create models. Mainstream mesh based SubD toolsets have gotten very refined over decades, the whole software architecture and workflow got optimized towards getting things done with SubD-methods. The simple geometry type is resources friendly – performance is great. Also subsequent processes which deal with the finished models were highly opimized towards quad mesh geometry as input:
Texture mapping, rigging and deformation based animation (character animation) rendering, physics simulation etc. Every Game Engine works with meshes.
Such programs are mature products, but one also has to state that users typically have output goals very different from CAD users: Physically producing stuff very rarely is of interest, hence precision never played a major role. What looks good on screen is very often good enough.

On the other hand there’s Nurbs based CAD programs which have been optimized over decades to deal with curves and surfaces – a workflow that has very little in common with editing geometry in Modo or Blender. Using Subdivision in CAD apps is a relatively young idea, far from mainstream, clearly at this point not suitable to replace Nurbs. This tech now gets implanted to programs which were optimized towards entirely other workflows, likely by programmers who only worked with Nurbs so far. The latter also applies to users of CAD packages – after years of Nurbification dealing with SubD is something entirely new to a lot of them as well.

SubD implementations in CAD have the problem that one needs to design a workflow which somehow fits established conventions. None of them thus far offers the fine-grained control one has at disposal in a dedicated SubD modeling application.

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Pretty clear explanation. Thanks.

thanks holger.

i was wondering if people were wanting Modo like subD in rhino which i personally thought might be a little weird (or not something i’d personally make much use of)… your explanation of mesh-based vs limit-surface clears this up for me.

Well, a handful of users would indeed prefer mesh based SubD (these users typically have a mesh modelling background) but probably most people here would choose the limit surface based approach. I personally do belong to the first group, although the latter seems so evident.

That said – I personally am not a great advocate for at all bringing SubD style modeling to Rhino as I find its ubiquous question>answer game (Select face to extrude: click, click) not a foundation for a SubD-editing workflow I personally would like. I described what I mean in a longer conversation with myself.

I would already be happy with better display, render + possibly Nurbs conversion support for 3rd party meshes.

cheers All, Holger

Spot on!

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@jeff_hammond

Here is the simplest way to look at it:

Does one’s creation need to ‘look right’, or ‘look right and be right’

Video games, animations, etc., primarily need to ‘look right’ on a screen.
Manufactured products need to ‘be right’.

Now look at the two categories described by hifred and consider the prime markets they cater to.

The hair in the soup – (that’s what I wrote a few posts further above) is that there’s no limit surface based
SubD modeling approach yet, which actually provides production grade geometry. Until now I see no added
value over utilizing any SubD-package and converting a carefully shaped mesh cage to Nurbs.

What – just as a game of thought – if one used the less stony path first?
With a mesh-based solution, one should have something pretty cool running after a year or so and likely also greatly better support for 3rd party created SubD meshes. One could convert all this stuff (native and imported) to Nurbs and would end up with the geometry quality one may achieve with popular SubD plugins for Rhino. Autodesk just announced EOL for Tsplines in Rhino…

McNeel could use more personnel resources for providing a truly convincing workflow, e.g. with a more feature rich Gumball, editing in symmetry, possibly the introduction of local coordinate-systems – all stuff which is crucial for SubD editing in general.

Users could slowly get their feet wet with a new modeling paradigm, had fun and got usable output.
The big brains at McNeel – as time allows and silently in the background – would crack some real tough problems having to do with Topology and Trimming and such. When done with all that one could swap the whole system to Limit Surface based. Any user who previously tried the mesh-based solution was well prepared – workflow and strategies remain the same.

Here’s some random web-collected geometry, which got modeled using Mesh-based SubD.

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oh, right, i know the difference between meshes and nurbs surfaces… it’s the exact reason i quit using sketchup and started using the early mac rhino beta (and have been using ever since)…

i could make some sweet renders with sketchup and a subdivide plugin but when it came time to build, the model was all but useless unless i needed to measure a point which was also a vertex on the mesh… i had some very convoluted workarounds in sketchup in order to get my vertices in the positions i needed to get measurements from and if something in the design needed changed, start over from the beginning.

my confusion regarding this thread was because people were saying ‘subdivide’ but not necessarily speaking of meshes… between david’s post and hifred’s, my confusion has been moreOrless cleared up since the distinction between mesh-based and limit surface based subD has been made.

Right…, Value add is SubD creation as efficient and accurate as possible: accurate meaning the design accuracy of the SubD, i.e., a specific section of the surface has a 10" radius in the Y direction and a 30" radius in X, whereas other regions of SubD may be more freeform (less need design accuracy)

Relative shape accuracy of a conversion is a given need…

Gotcha. Used your question to illustrate a point. It was @DavidRutten accuracy statement I was keying on. Hoping McNeel SubD focuses on innovative means for defining design creation accuracy, when needed, in a manner similar to what is possible with NURBS, which has been a mainstay. This is where a value add will come from.

Thanks for allowing me to do so. Not questioning your understanding. I did not make that clear. Read long thread quickly.

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@jeff_hammond Have you tried machining on a dense mesh? It apparently isn’t possible or I haven’t figured out how. Which, if true, makes it out of the question for doing any production of terrain models…
–Mitch

nope, i’ve never tried machining mesh geometry yet. (with any application for that matter).

i know fusion just gained a bunch of mesh tools (they may still need specifically enabled per user?) but i don’t know if this means anything for CAM.

so, in short, i don’t have any helpful info regarding this :wink:

Yeah, apparently they need to convert the thing to surfaces before machining… Which means stuff like the following (1m polygon mesh) is currently out of the question.

It is a bit surprising to me as ADesk own Delcam and ArtCam, both of which can machine on meshes…

–Mitch

Mitch,
the model should look ok with a some hundredthousand faces. Is that already too much for the CNC program you are using? Does toolpath creation take forever?

In case you badly need a surface model from this one, I might be able to help.

[quote=“jeff_hammond, post:72, topic:37603”]
I know fusion just gained a bunch of mesh tools (they may still need specifically enabled per user?) but i don’t know if this means anything for CAM.[/quote]

Fusion’s CAM workspace indeed can only handle surface data. One can load quad meshes but needs their
internal Tsplines (Sculpt) workspace to convert polygons to Nurbs.

i’m not too in the know about this kind of software but i believe fusion’s CAM is, or is based off, HSMworks.

Nope. No time at all, as you can’t even select the model. :stuck_out_tongue_winking_eye:

Nope, just testing today, and my first test here pretty much ruled it out for our use.

–Mitch

So how heavy is the mesh?

Just an note of interest…

Almost all, if not all, CAM products convert NURBS to meshes internally before doing the tool path calculation.

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