Can anyone tell me why every time I fillet either it will fail or do what's in the image. How can I avoid this from happening? Its very frustrating. Thanks for any help. File attached.

Hi Billa, shapes like this which come fairly close to being smooth to each other but are actually just slightly sharp tend to be difficult to fillet:



That's because fillets shrink down to a point in a spot that is smooth. So for a spot that is close to being smooth it will shrink down to a small size there and be difficult to extend and intersect with surrounding faces.

It would probably be good to have this as one long smooth surface rather than a patchwork:



There is a fair amount of warping on the patched connection pieces.

A couple of other things are that it's harder for the filleter to process things when you're only filleting some of the edges that come out from a shared endpoint instead of all of the edges because then it has to try an intersect the fillets with each other. When all of the sharp edges coming out from one point are being filleted it will be able to make a corner juncture patch for that spot rather than having to deal with fillets directly running into each other.

One more thing too is that it's good for areas that are coplanar to be made up of just one big plane instead of multiple coplanar fragments.

- Michael

Hey Michael,

OK so I understand now the reason why it wont fillet, but what I dont understand is how else would I have created this piece? I Used a loft, created by the outline of that object space out 4 times. I tried using a sweep but even with a sharp rail, it would make that slant, very wobbly. I guess Im a little confused by your comment of "just one big plane instead of multiple coplanar fragments"

As always, thanks for your patience and help.

-B

Hi Billa,

re:
"just one big plane instead of multiple coplanar fragments"

That means that instead of this (here are 2 coplanar fragments):



For helping with fillets you instead generally want just one face there:



To do that quickly you can use boolean union when gluing the halves together instead of join. It is kind of a good practice to use Join when you don't need pieces to be intersected but here it would be good to have those planes fused together which boolean union will do.

- Michael

Hi Billa,

re:
> but what I dont understand is how else would I have created this piece? I Used a loft, created
> by the outline of that object space out 4 times.

I'm thinking about that...

The piece that I don't like is this one:



It kind of torques quite a bit in a relatively small space. It's hard to make a sweep that banks around in a small zone like that too though.

One thing that might be workable is to separate things out into strips like this:



Fillet should not have difficulty on those if the pieces are not joined to the other side pieces.

- Michael

ok that makes sense, but what about this side? I tried making it one smooth plane, by deleting the faces and lofting, which didn't work and i tried using network, which didn't work either. So how would I get away with one smooth plane, on angles like this?

Another thing that is complicating things a little bit is back here:





- Michael

damn, I didnt even see that. Thanks!

Hi Billa,

re:
> ok that makes sense, but what about this side? I tried making it one smooth plane, by deleting the faces and
> lofting, which didn't work and i tried using network, which didn't work either. So how would I get away with
> one smooth plane, on angles like this?

You'd need something like a sweep that has long smooth rails running the whole length of the piece. It would need to be extended a bit so that it pushed through the surrounding surfaces and so could have its excess outer zone trimmed away.

But that middle zone changes shape quite a bit in a small area and that makes it harder.

What is the end result that you're looking for, is it everything being filleted or do you want some edges to be sharp in the end?

- Michael

Also what fillet radius do you want?

- Michael

So the end result will be the attached image. I've been working in 3ds max over 14 years and only recently made the jump to nurbs, So for me it feels like starting completely over with the learning, but I am creating everything right now with sharp edges, which will be my base for a low poly model, that will be exported to max and unwrapped. once I create the low poly. All edges will be filleted. This is needed for the baking process from high to low.

I tried using a sweep, but that middle section got very wavy and I could not get that to straighten out. Which is why i ended up using a loft with 4 profiles.

Hi Billa, so here's the thing to get used to, when you have an area like this to surface:



If that's all one smooth surface making a kind of smooth "sheet" form without any sharp bends or transitions within it, then it's good for that to be made out of one single surface.

However, the piece you want to build is an extended form that has a simpler structure to it. you want to temporarily ignore the boundaries of the final result, instead you need to make relaxed boundaries of a larger extended surface like this:



Then the end edges are going to be formed by intersecting some of these broad extended sheets with each other, rather than drawing in all the edges and trying to construct surfaces directly to those end edges. The end edges are too irregular here to be used to directly construct a surface from, they need to be a trim boundary (formed by boolean or trim) on a larger underlying surface rather than directly being the edges of a constructed surface.

This concept of extended surfaces that intersect each other is one of the main differences between NURBS modeling and poly modeling.

There are some tips here for people coming from a poly modeling background, they may be helpful:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

- Michael

Thank you Michael. Ill try that and let you know how it goes. Also thanks for the link. I'll go through it as well, before I ask anymore questions. I do apologize for so many posts in the past few weeks but I appreciate you helping so much.

-B

Hi Billa, no problem - it is a big transition from poly modeling. This concept of making broader extended surfaces is a key thing.

Do you still want this existing model to get filleted? I have been having success working on some separated strips and I can probably get it filleted if you still want and if you let me know what radius you want:



- Michael

Hey Michael,

Thank you but I really want to understand this and I'm afraid if I grab this model from you. Ill just use it and move one. So if I understood you correctly. I made extended sheets intersecting themselves, like in the attached image. Is this correct?

Hi Billa, that's a step in the right direction but not quite all the way.

So let me explain a little bit of analysis on the reference image.

Looking at this surface here:


Which is the one you're trying to make here:


It doesn't bend or warp throughout the entire surface, it looks like it's probably a plane actually. Even in this area here:


even though there are curved shapes there:



those curved shapes are not having any influence on the surface shape, that's telling me that those curves are purely trim boundaries on a larger underlying surface, those curves are not influencing the shape of the surface itself and so you should not be trying to build that surface by any kind of loft or sweep that's trying to use those boundary curves. Those curved edges will be the result of a trim or boolean, not part of a surface construction method.

So the surface you want to initially construct for that area is going to be a much larger piece that completely and totally ignores those curves initially, like this:


So applying this more broadly to other areas as well there is a base underlying form of the entire model like this:


So that's actually what you want to construct first like this:



The front slant and level change are introduced by drawing in a side profile:



And then doing a boolean difference using the side profile as the cutting object, which divides it into 2 pieces, then you discard this piece:



Then you're left with this:



You'd do another boolean something like this to cut away this area:





So it can help to think more of how the actual physical part might be machined, you start with some stock and pieces are cut off of that stock. This is in contrast to starting off by drawing all the final edges and then trying to build surfaces in between them which is more of how you'd do things with poly modeling.

Hope that makes more sense!

Then the part that will be a little trickier is there is one piece that is made up of a curved surface that is influenced by the shape of a curved boundary:



So for just that one area, that's the spot that you would using the type of surface construction that you were previously trying to use for everywhere.

I'd have to look at that a little more when you get to that stage, that could maybe be a loft between edges or it's also possible to do a sweep that's slightly extended and then used as a cutting object in boolean difference:



- Michael

Wow! I was way off. The way you explained it, makes it seem a lot more simpler. I feel like I was making it lot more complicated than it had to be. Thank you so much for the detailed explanation Michael!

-B

Hi Billa, you're welcome! So it is very easy for someone with a background in poly modeling to approach it the way you were doing it initially. In poly modeling you're usually avoiding booleans entirely while in NURBS modeling you want to have booleans as the main preferred strategy. Part of that is trying to focus on an initial larger extended shape.

If you find yourself doing a whole lot of filling in pieces with loft or network that can be an indicator that you're not going in the optimal path for NURBS modeling.

- Michael