Hi, its my third day with Moi and I just finished this Clipper lighter. It went ok but there where a couple of bits that I got stuck on.

One was the ridge under the gas button and its fillets to the main cylinder which I couldn't get to look nice. They look dodgy all the way round.







The other was the yolk piece that holds the flint wheel. Couldn't work out a good way to make it brain freeze.






Heres the file if you want to look.

Oh yeah and Pics :)

Hi Wheel - this is an awesome result after only using MoI for 3 days and being new to NURBS modeling as well!

Some answers to your questions...

On this one:



That actually shouldn't be a problem - the fillet in that area is properly formed, just as a way to help some of its own internal calculations the filleter may sometimes split larger fillets into 2 pieces like that, but the shaping is properly formed there.

For example if I export to an .obj file, you can see that area looks fine:




This area here:



is not so well formed, but it is a very difficult type of corner situation to put a really great quality shape in. If you want a better shape, you kind of have to change the approach a bit so that the corner is not so severe there - that usually means placing a fillet on the protruding part first, before applying the fillet to where the pieces meet.

What I mean is say for example I want to fillet this object:



If I only try to fillet these edges here:



That creates a difficult corner situation:



It is tough to get something nice when there is a sharp-edged shape thrown into the mix there.

On the other hand, if you fillet these edges first:



That will create this type of shape:



Now that original place we wanted to fillet is traveling along a completely smooth path, a smooth path helps to make nicer corners:




Your other question on this piece:



Those narrow vertical pieces are not quite vertical, they have like a 1 degree angle or so to them, so they don't mate up completely nicely with the box below them.

If you want to build things by kind of carving or joining little pieces, it helps a lot more make sure there is a lot of accuracy and matching between the pieces. Things that are slightly angled or positioned slightly off will tend to cause little slivery bits to happen when they cut one another, those slivery bits will cause problems with filleting.

Let me know if you are still stuck on this piece and I can help you rebuild it if so.

- Michael

Also on that last flint holder piece, I think you've got some of the arcs and lines drawn in such a way that the line coming off the arc is not quite tangent to the arc but pretty close to it. That kind of very shallow angle between curves will tend to make problems with filleting later on - it is better when things that are within a few degrees of being tangent are built using snapping methods to make them precisely tangent instead of just almost tangent.

Basically, if things are sharp, that's ok, and if they are tangent that's ok, but it is a problem when they are in a kind of no-man's land of not tangent but within a couple degrees of being so.

- Michael

Thanks for your kind words and advice. I'm really comfortable with the way Moi works after going through the tutorials. It feels natural and intuitive very quickly.

>>Fillet then Join.

Ah ok that looks much better. I'll try that again and do some little tests like you've shown. I figured it was a tricky join but your example makes it very clear, :)

>>Not vertical. Arcs and tangents not quite aligned.

I was getting slivery bits joining these parts. This was why... I see. That was the best join I could get, I must have nudged them off vert at some point while tweaking. I didnt use the " Arc tangent " tool on those side profiles either, I just eyeballed it...oops . I'll look into that in the docs.

I've got lots of ideas to play with now. Thanks for your time, suggestions and explanations. They are much appreciated. Regards Wheel.

Hi Wheel,

> I didnt use the " Arc tangent " tool on those side profiles either,
> I just eyeballed it...oops .

Yeah, just eyeballing it tends to cause problems with filleting later on down the road. Filleting is pretty finicky about that.


But actually, Arc tangent is probably something to use more for special circumstances and not really so frequently.

A few things that can work a bit more easily are first all instead of manually drawing in arcs by hand, you can use the fillet command on a polyline to replace corners of the polyline with automatically calculated tangent arcs.

I mean like for example if you have a shape like this:



You can then select it and run Construct / Fillet - that will allow you to pick corners of the curve to fillet:



Then you pick a radius (same as filleting an edge of a solid), and that will create tangent arcs for you:



If you have something made up of lines and arcs this tends to be the best way, just draw all the lines first, get the pieces joined together into one curve and then fillet them.

Then you don't have to actually mess around with drawing any arcs manually at all.

However, in the case where you have a big arc piece like you did in your example that needs something slightly different.

With a big arc piece instead of a corner arc piece, I would actually draw the big arc first instead of the lines first, like this:



Then there are some straightforward lines that can be drawn - make sure you have "Straight Snap" enabled while drawing these so you can see them snap vertically or horizontally:



Now to draw the final line such that is matches up tangent to the arc, you would start it at the bottom point, then as you move up to the arc you can find a "Tan" object snap on it that will be the point where the line is tangent to that arc, like this:








So you can see there that I drew the arc a big bigger to start with on purpose, so that I could find that snap point on it later on. In fact you could draw in a full circle there instead of an arc if you wanted.

Then to finish, you select the arc, and use Edit/Trim to cut off the excess part:



Using Trim like this to clean off excess bits can make it easier to construct things rather than only working exclusively off of the very ends of things all the time which tends to require some more careful planning to make sure everything is all precise (for tangent arc pieces).


Hope this is useful!

- Michael

Tricky!

I have rebuilt the main body and joined the ridge part as you suggested. Its much better with your instructions thanks. Remaking the body ontop of the old one worked out pretty easy aswell, just snapping circles to circles and making sure I had the right bits selected before boolean diff subtracting and merging pieces.






The flint holder was going well. I made the profile curves as suggested, vertical lines and tangent arcs. I extruded the curves and then boolean diff subtracted out a cube from the middle, but couldn't get the fillets to work on the inside edges. I was suspicious of the little straight part at the bottom so removed that and tried the above steps again and the fillets worked fine. Sweetness.







Thanks for your help sorting these bits out, its a fun and refreshing change using Moi to my regular poly modelling toolsets.

Hi Wheel, that is great progress.

> I was suspicious of the little straight part at the bottom
> so removed that and tried the above steps again and the
> fillets worked fine. Sweetness.

You've gotten the hang of NURBS modeling very quickly, even to the point of knowing which things the filleter doesn't like! :)

Yeah co-planar bits split up into multiple small pieces tends to bother it right now.

You've already fixed it, but just a note on the quickest way to do so - you can delete those 2 co-planar pieces, then select the whole object that now has a hole in it, and use Construct/Planar to fill in the larger planar hole. There is stuff in the booleans that tries to do this automatically but there are some circumstances where it doesn't work yet.

Construct/Planar can be used to either create a trimmed plane surface from a set of planar curves, or it will also fill in planar open holes on surface/solid type models.

If it doesn't fill, then it means something is not planar there - that was actually the first clue to me that something was slightly off on your original shape.


> Thanks for your help sorting these bits out, its a fun and refreshing
> change using Moi to my regular poly modelling toolsets.

You're welcome, and I'm glad you are having fun using MoI!

It's nice to have the combination of both of these different kinds of toolsets available to you, depending on the type of model you are currently building.

- Michael