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