Feature idea: blended fusion

[jnxd]

It will be interesting to see how you handle the situation where two faces converge... I was looking for an example I saw on the Reddit CAD Challenge some time ago, but can't find it now.

By two faces converging do you mean a case where a fillet would effectively become an edge? In terms of reality, that is almost never the case, so a practical implementation should have options where one puts in what kind of a "fit" is needed. Think clearance, interference, or transition fit for bores and shafts. I can't think of any practical cases where fillets are imvolved.

On a slight aside these border cases should be incorporated into the implementation of toponaming too. TODO: discuss jman's case.

[bejant]

By two faces converging do you mean a case where a fillet would effectively become an edge?

Yes, I suppose that's one way of looking at it (I was thinking that the Fillet would become a point at the seams); the example I had in mind was trying to Fillet something like this edge:

20170507-FilletGlitch.png (10.32 KiB) Viewed 1301 times

20170507a-FilletGlitch.fcstd

(10.2 KiB) Downloaded 21 times

I used the Part WB to create the shape but Part WB > Fillets fail as does 0.17 PartDesign Fillet (I need to update):

OS: Ubuntu 16.04.2 LTS
Word size of OS: 32-bit
Word size of FreeCAD: 32-bit
Version: 0.17.10949 (Git)
Build type: None
Branch: master
Hash: 20828b3cb31557301da66465363717e1e66c28c7
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.1.0

[jnxd]

Yes, I suppose that's one way of looking at it (I was thinking that the Fillet would become a point at the seams); the example I had in mind was trying to Fillet something like this edge:
20170507-FilletGlitch.png
20170507a-FilletGlitch.fcstd

This is indeed a puzzling case. We might have to start from scratch here regarding what one means by a fillet. Specifically, how is it defined near the point.

[tanderson69]

Anytime you have a variable fillet that ends with a 0.0 radius, you have a poor condition. This is true for any modeling kernel. It is one of those things you learn to avoid if you can. For that case, I would try for a constant fillet. something like:

filletHacked.png (23.48 KiB) Viewed 1276 times

IMHO: These situations that present problems for the modeling kernel are outside the scope of a freecad feature.

[bejant]

In this case I'd like to see a constant radius for the portion of the edge where it is possible, given the radius chosen by the user. For the portions of the edge where a constant radius is not possible (as the edge nears the seam), I think it would be better if the user had the option to allow the radius taper to a point, instead of a fail as it happens now.

Anytime you have a variable fillet that ends with a 0.0 radius, you have a poor condition. This is true for any modeling kernel. It is one of those things you learn to avoid if you can.

But in the instances where it can't be avoided, I'd like the ability to create a fillet (or chamfer) instead of seeing the operation fail.

IMHO: These situations that present problems for the modeling kernel are outside the scope of a freecad feature.

I'm not sure this is a CAD kernel limitation (I can create a Part WB > Fillet of the type Variable Radius that taperd to zero). In the case of the two cylinders I was thinking the radius would be:
0 to User Value (where possible) to 0.

[tanderson69]

In this case I'd like to see a constant radius for the portion of the edge where it is possible, given the radius chosen by the user. For the portions of the edge where a constant radius is not possible (as the edge nears the seam), I think it would be better if the user had the option to allow the radius taper to a point, instead of a fail as it happens now.

Anytime you have a variable fillet that ends with a 0.0 radius, you have a poor condition. This is true for any modeling kernel. It is one of those things you learn to avoid if you can.

But in the instances where it can't be avoided, I'd like the ability to create a fillet (or chamfer) instead of seeing the operation fail.

IMHO: These situations that present problems for the modeling kernel are outside the scope of a freecad feature.

I'm not sure this is a CAD kernel limitation (I can create a Part WB > Fillet of the type Variable Radius that taperd to zero). In the case of the two cylinders I was thinking the radius would be:
0 to User Value (where possible) to 0.

So what you are really saying is: "I want a robust way to specify a variable blend"? No doubt! Even when you get it, in this case, you will just be making corrupt models instead of the feature failing.

variableFilletError.png (50.94 KiB) Viewed 1217 times

I don't think this has anything to do with DeepSOIC blended fusion feature proposal. I think we should stop hijacking this thread.

[bejant]

So what you are really saying is: "I want a robust way to specify a variable blend"?

No, not exactly...

I saw the first post in this topic by DeepSOIC which reads

The idea: for operations that do fusions/cuts, it is possible to find edges where shapes being fused/cut intersect, and add fillets or chamfers there.

and was reminded of some trouble that happens with Fillets and Chamfers, and my reply was about that.

As a user I think this new Blended Fusion / Cut tool will be handy and would like to see it have the capability to handle the use case I wrote about. If the Fillet / Chamfer tools get improved along the way too I'd consider that to be an added benefit.

Even when you get it, in this case, you will just be making corrupt models instead of the feature failing.

Well, obviously nobody wants to create a corrupt model or see the feature fail. I'd like the Blended Fusion / Cut tool to be so robust that I can fearlessly add Fillets and Chamfers anywhere in the modeling process instead of at the end.

I don't think this has anything to do with DeepSOIC blended fusion feature proposal. I think we should stop hijacking this thread.

I thought it was relevant so I replied but now I think I've explained well enough...

[industromatic]

I've not used FreeCAD since

viewtopic.php?f=3&t=13071&p=104732#p104732

1.5 years ago, but this sounds like things may have improved some, but still, order of operations matters very much?

I'm planning to use FreeCAD again for a part that is to be milled, but then the same thing could be molded
later on with draft angles required, and fillets required. For now, with milling of parts, fillets can be left off when they are
concave -- just use a round ended mill with a sharp inside corner shaped model and all will be filleted as it is made even
though no fillets in the model.

So, are things working as well or better than 1.5 years ago re: BREP fillets to be done last
after all booleans create CSG models?

[DeepSOIC]

1.5 years ago, but this sounds like things may have improved some, but still, order of operations matters very much?

I'm afraid, not much has improved in regard to fillets... if anything at all

We've experimented a bit today in direction of blended fusion, and got some success, but... not very encouraging. I leave it to jnxd to report more details

[industromatic]

If it has held and not gone backwards, that's good. Thanks for all you do keeping some free open CAD going instead of absolutely having to buy something like Rhino3D with a student low price and not have the source code...

Maybe BRL-CAD will complete some of their documentation goals and become usable. I've never gotten much benefit out of it, but FreeCAD has plenty of benefit. I've done a combo of Solvespace with FreeCAD to finish to create swept shapes suitable for plastic molding. I'll be doing it again soon.