Filleting
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 From:  Michael Gibson
2048.17 In reply to 2048.11 
Hi PaQ,

> As you're talking about it, will Viacad (pro) be a better alternative
> than rhino to extend my actuall MoI toolset ?

Well, it all depends on what you want to do.

Viacad would be better for things along the "Mechanical CAD" or "Solid modeling" direction (for example, shelling & fillets), while Rhino would be better for stuff along the "Industrial Design" and "Surface styling" type direction (flowing surface type stuff).

Neither one really covers the other area very well.


> For the moment I switch time to time to rhino for :
>
> - the surface continuity option with the sweep or network tool
> - the patch tool
> - sometimes to use the sweep tool when Moi's distribution
> failed to give a nice result.

This is the kind of surfacing stuff that would do better in Rhino. I think that some of this is present in ViaCAD as well, but is kind of like an afterthought over there and not really set up very well (in my opinion).


> As I'm still a noob in this cad world, I don't really get the
> difference between viacad and Moi/Rhino nurbs library.

Well, they all use different libraries. So they tend to have different sets of bugs and different weak and strong areas.

The one used by ViaCAD is used by many "parametric solid modeling" / Mechanical CAD programs though and has a lot more development time spent in the areas of filleting and shelling in particular.


> You suggest to give a try to viacad, is difference so huge about filleting
> stuff. It happends in some case that I'm stuck
> with some fillets, even if it happends less and less. And most of
> the time if a fillet failed in MoI, Rhino will not really help either.

No, it is not very likely that Rhino will help out for filleting. There probably are a few cases where Rhino could do a fillet where MoI had problems, but much more of the time I think it is the other way around where MoI handles fillets that Rhino has problems with.

And Rhino does not currently even have a shell function at all, so it is zero help for that. Shelling is a pretty good area of ViaCAD though.


> Viacad pro seems to have some nice tools in :
>
> - Bending Along Curve ... well why not (are they using
> construction history to handle this ?)

No, they use some code in the ACIS "Deformable modeling" library to do this, being able to bend things depends on a bunch of code that calculates the bent object, having construction history doesn't really have anything to do with it.

But this is an area that would probably be handled better by Rhino, that have a nice set of new tools in v4 for deforming objects.


> - Offset Surfaces : would it be a little better than MoI's one ?

Yup, this would be a strong area of ViaCAD.


> - Skin with Guide Curves ... don't really get the concept

I think it is their version of 2-rail sweep.


> - Surface Matching ... sounds cool, and seems to be performed
> after the surface creation, not sure if it will work on imported models

Should work fine with imported surfaces, but probably again I'd go for Rhino with this kind of "surface styling" oriented task.


> - Tangent Covers ... well seems to be a patch tool right ?

I think so.


> Would like to have an advice about it, the workflow seems really
> different from MoI and I'm affraid by the learning curve :S

Yeah, one downside of ViaCAD is that it is kind of based off of an older line of programs, it has a lot of legacy remnants in the way that it works. It would probably take a bit to get used to actually creating things from scratch in it.

I'd generally recommend to use it mostly for filleting and shelling pieces, if you just focus on those particular tools that would probably get the optimal use out of it with least frustration.

- Michael
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 From:  Michael Gibson
2048.18 In reply to 2048.12 
Hi Brian, no problem. I'm sorry that filleting gives so much trouble it is unfortunately a quite sensitive and complex calculation involved with it.

It looks like PaQ has given some great steps above there for how to make a more totally "fillet friendly" shape.

I took a look at your model, and it actually your existing model seems to fillet ok for me at a small radius value like radius of 0.2 .


So after doing that, here is a look at that front edge that PaQ was referring to:



Zooming in:




You can see there that since those pieces do not meet smoothly, it forces the filleter to try and splice in a kind of corner connection piece between them. Making those smooth to one another will eliminate that and helps makes a more simple fillet structure there, that can help.

Then the other thing is notice how this "seam" edge is pretty close here:



Probably the #1 problem with fillets currently is that it will not cross a nearby edge like that, it will only approach it. So currently it tends to be best to make your part actually cut through the seam instead of come close to it, that avoids that issue.

- Michael

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 From:  Brian (BWTR)
2048.19 In reply to 2048.18 
PaQ, Michael
Thanks for all that brilliant help.

WOW!

The study/think cap is going to be busy again today.

Brian
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 From:  Brian (BWTR)
2048.20 In reply to 2048.19 
As a PS side note!

I saved the MoI file as an OBJ file and took it into a polly modeller to try filleting there.@#%&**

MoI is GREAT!

Brian
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 From:  PaQ
2048.21 
You're welcome Brian, I'm happy if it was helpfull somehow :)

Thanks Michael for the little nurbs lesson here.
I don't think I will invest to much time to learn viacad if it's only to use it 3 times/month just for some fillet issue ... but I will play with it a little bit during the evaluation time.

I can't wait to see how MoI will grow too :o)
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 From:  Michael Gibson
2048.22 In reply to 2048.21 
Hi PaQ - the other kind of very different area that ViaCAD is good at is in sort of blueprint style 2D drafting. I think it's got stuff like generation of 2D plans from a 3D model, and easy to use dimensioning tools.

But probably for your kind of work that would not really come into play much.

Rhino has some of that stuff as well, but that is a pretty good area for ViaCAD also.

- Michael
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 From:  PaQ
2048.23 In reply to 2048.22 
Hello Michael

> the other kind of very different area that ViaCAD is good at is in sort of blueprint style 2D drafting. I think it's got stuff like generation of 2D plans from a 3D model, and easy to use dimensioning tools.

Well it might be funny for creating some techno artwork or background, but indeed it's not something I need in my daily work ;)
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 From:  steve (STEEVE)
2048.24 In reply to 2048.13 
>Looking at the profile curve of the wing, there is indeed probably a discontinuity in this area, the 3 points (red lines) should fit on one line.

Very nice trick PAQ, moving the offending point in line with its neighbours.

I was just about to post a filleting question, but now I don't need to :)
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 From:  Frenchy Pilou (PILOU)
2048.25 In reply to 2048.13 
@Pac you say I draw a line (for align the 3 points)
but you can also use the "helpers" lines for draw this line ;)
---
Pilou
Is beautiful that please without concept!
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