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 From:  Cube
5491.1 
Hello,
Just having a play and was trying to create an object with a variable fillet.
The fillet part i managed fine using dual rail sweeps, but this left the need to build the rest around this, and then fill in the top surface (see pics). In the end I found a few posts and using a combination of instructions; I selected the top 'edge', 'copy and pasted' it and then extruded it out. Next i 'copy and pasted' the same top 'edge' and squashed it 'flat' then extruded it out to intersect the other extrusion. Next i used a 'Boolean Isect' ('Boolean Diff' kept top part and removed the bottom) My question is was the best way to fill the top hole?
I have a feeling this top surface may not be as it seems, if i try to 'Boolean Union' it to the rest it goes a bit odd.






















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 From:  bemfarmer
5491.2 
Please post .3dm file.
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 From:  TpwUK
5491.3 In reply to 5491.1 
Hi Cube, if you are playing with version 3 beta (the latest one) then there is a more variable network surface option. Draw a curve using the three point curve option, draw it from the middle of the top edge to the bottom edge mid point and then adjust its curvature to suit, then select the four outer edges of the hole, then the new curve you just did, and click network surface.

Hope that helps

Martin
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 From:  Cube
5491.4 In reply to 5491.3 
Sorry can't post the 3dm as I was just having a play in the save disabled version. Will be purchasing but probably wont be for a month or so.
So is the way I did it a valid way of construction or am i going to run into problem later (i.e coplaner faces)
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 From:  Michael Gibson
5491.5 In reply to 5491.1 
Hi Cube, yes can you please post the 3DM file? It's a lot easier to see what's going on by examining a 3DM file since it's then possible to look at the actual geometry an zoom in, look at different angles, etc... which can't be easily done just by looking at a screenshot alone.

When you get a weird looking result that has chunks missing from it or "leaking out" like that, it usually means that there is some problem with the trimming boundaries of that particular surface piece, they're probably mangled in some way like having pieces cross over themselves or things like that. That can be possibly the result of a bug, or it can also be the result of bad geometry inputs like having some original curves with little loops in them or similar stuff.

But it can be difficult to build a good quality model going in a "patch by patch" method like you're doing here because if you just build different surfaces next to one another they will usually not match up smoothly between each other and there will be a sharp crease in your model there.

Usually to get a good smooth model you would need to use filleting or blend which are the main construction tools that ensure smoothness of the stuff that they generate to the surrounding surfaces.

EDIT: sorry was writing this while you posted your reply above and so didn't see it.

- Michael
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 From:  Cube
5491.6 In reply to 5491.4 
btw I should add that the boolean problem was when I was trying to just boolean the top surface of the orange central fill object.
on reflection I think the issues could be trying to boolean just a single surface?
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 From:  Michael Gibson
5491.7 In reply to 5491.4 
Hi Cube,

> So is the way I did it a valid way of construction or am i going to run
> into problem later (i.e coplaner faces)

It's valid as long as you don't mind that there's going to be sharp creases between each of the separate pieces that you've constructed...

The most simple way to fill in a hole like you've got on the top there can be to divide the closed curve into 2 halves and then do a loft between the halves. But even though that will fill in the hole it won't make a smooth connection to the surrounding surfaces.

Usually in order to make things smooth with NURBS you would construct the bigger broader pieces first and then do fillets and blends to form the transition areas, building only the transition areas first is kind of reverse from the regular way that you'd try to approach it.

If you definitely need a variable radius fillet, then probably the easiest way would be to bring your geometry into a different CAD program that can do variable radius fillets right now, ViaCAD is a good option for doing that: http://www.punchcad.com/p-9-viacad-2d3d-v8.aspx

- Michael
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 From:  Michael Gibson
5491.8 In reply to 5491.6 
Hi Cube,

> btw I should add that the boolean problem was when I was trying to just boolean
> the top surface of the orange central fill object.
> on reflection I think the issues could be trying to boolean just a single surface?

Yeah usually booleans are done between solids, or a solid with a surface cutting it, and not just 2 open surfaces cutting each other.

If you need to cut 2 surfaces with each other you can use the Edit > Trim command for that kind of cutting - basically the booleans are like a "batch mode" version of trim where they do trimming plus figuring out which areas to keep or discard based on what solid volume they are contained inside of and then joining up the results.

They can save time because they combine several tools together like that, but the main way that they do that combination is by part of the process working according to volumes. So if you don't have solids yet you can instead do each of those types of operations directly by the lower level tools like Edit > Trim and Edit > Join. Then with the "low level" trim tool instead of it automatically deciding which pieces to discard based on volume it instead slices them up and lets you specifically pick which pieces to discard.

But if you're doing this type of individual surface construction, it sort of means you're not really fully utilizing the optimal way to build NURBS objects because you're doing things the advanced and low level way instead of speedy way doing solids. Sometimes you need to do things the low level way if you're doing a lot of custom surfacing but if what you really need is a variable radius fillet, I'd recommend bringing your object into a different CAD program and then doing the variable radius fillet there and then bringing it back into MoI, that will be the most time effective way to get things done for a variable radius fillet right now.

- Michael
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 From:  Cube
5491.9 In reply to 5491.7 
thanks, guess it's just a case of getting used to different way of modeling.

EDIT - Always quite enjoyed finding work-a-rounds when modeling :-)
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 From:  Michael Gibson
5491.10 In reply to 5491.9 
Hi Cube, yes NURBS modeling is a pretty different method from polygon modeling.

One of the things that tends to be hardest for people to get used to is the idea of building bigger extended pieces and then cutting them with one another as the main method to produce shapes. People from polygon modeling backgrounds often want to put in the final edges and then patch things in from there.

But usually with NURBS modeling you don't want to specifically draw all the final edges yourself, you want to try and draw mostly 2D curves then make some pieces from 2D curves and produce some areas by cutting with the 2D curves and with that method many of the 3D edges of your final model are formed not by your own direct drawing them but by intersections calculated between the larger pieces.

The good thing though is that when you get into the groove with this method you can produce a lot of stuff really quickly since you can make a lot of stuff happen all from 2D curves.

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


The more sort of generally blobby-ish and organic your shape is then the less it is very well defined only by 2D profile curves and such shapes are usually a better fit for polygon modeling rather than NURBS modeling.

- Michael
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 From:  BurrMan
5491.11 In reply to 5491.9 
Me too....
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 From:  Cube
5491.12 In reply to 5491.11 
BurrMan,
Could you give me a quick rundown on how you built that as a single solid?
Thanks,
Steve

EDITED: 20 Oct 2012 by CUBE

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 From:  BurrMan
5491.13 In reply to 5491.12 
I used 2 parts to create a blend, then removed one of the parts. Here's an example with the 2 surfaces. After blending, I deleted the bottom surface, then miirored the 2 top ones down. They can be connected and joined. For your example I used a "loft" because your model looks straight on the sides.. You could connect them with blend also, for a smoother look.

I think in the example I posted I trimmed the blend up from the bottom a little too, before I mirrored it.
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 From:  Cube
5491.14 In reply to 5491.13 
Excellent thank you very much. I hadn't thought to use blend here, its not one of the tools ive played about with much.
I think I need to spend some time on the basics and getting used the different way of modeling... but thanks for your input that is very useful.
It's odd but I find myself really enjoying using Moi in the same way i used to enjoy sketching, even after a long day doing 3ds max and comping (which is far less enjoyable! - surprising what difference a nice interface and great anti-aliasing can do), never thought id find myself enjoying 3d modeling again.
Appreciate peoples time.


EDIT - Just tried your method, and although a slightly different shape as I was not following any guide, I managed to get the principle shape in about 5 mins as opposed to about half of hour messing on Friday. (just tested its construction by booleaning out a massive hole)
Will also have a proper read through Mike K4ICY tutoral as I should have done initially.

EDITED: 21 Oct 2012 by CUBE

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 From:  Cube
5491.15 In reply to 5491.14 
Question, just having another go at this method but im getting a little gap between one of my blends, is this quite a common problem?
Anything you can do to avoid it?
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 From:  TpwUK
5491.16 In reply to 5491.15 
You're zoomed in pretty close there Cube, so it might be related to mesh angle. There are two things you can to try and fix this. Join the surfaces together with the join command, or if they are already joined, then go to options and select View and set the mesh angle to a lower number say 10 or even 5 since you are working on a smallish model

HTH ...

Martin
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 From:  Cube
5491.17 In reply to 5491.16 
Hello,
It's not just a display issue (I also wondered this), there is a gap, when I join all the surfaces together on this one it just comes out as one 'joined surface' rather than the 'solid' of the previous one.
Also if i try to use the 'Merge' function on the edges a couple of them just wont merge together.... I was going to 'Merge' then trim slightly differently.
Anyway i'm going to install the demo on my work machine tomorrow so if I can recreate the problem ill post a 3dm file.

Thanks.
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 From:  Michael Gibson
5491.18 In reply to 5491.15 
Hi Cube,

> Question, just having another go at this method but im getting a little gap
> between one of my blends, is this quite a common problem?

Yeah that can be a common problem when doing blends in multiple pieces - it looks like your lower surfaces are probably not smooth where they meet and that means that the different blend surfaces (which adapt themselves to be smooth to the surfaces involved) will bulge out in slightly different ways and then not meet up along their side walls like you show there.

In a case like that you'd need to use Network or Sweep to generate the surface instead because with those commands you can specify the "side rails" of the surface instead of only leaving the sides to be auto calculated like they are in Blend.

This problem should also be solved when Blend is updated to be able to do a longer chain of edges all in one pass rather than being limited to only be between one single edge to another single edge. I'm hoping to update Blend for that before v3 is finished.

Previously it has not been a #1 focus to get that kind of Trim + Blend style modeling as a primary method of model construction because really if you're doing that kind of modeling you're most likely trying to organic shape modeling in NURBS and that's the kind of modeling that is really best suited for polygonal sub-d modeling instead of trying to do it in NURBS in the first place. It's been more of a focus for MoI to try and perfect more of the stronger areas of NURBS modeling initially first which is more stuff like doing booleans with 2D curves as cutting objects and things like that.

When you're getting into Trim + Blend style modeling there is only really a basic level of that set up currently in MoI, so you're running into some of the limitations in that area currently.

I do expect to reduce some of these limits here in the v3 timeframe though.

- Michael
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 From:  Cube
5491.19 In reply to 5491.18 
Hi Michael,
I have attached a sample file.
A - Is the initial construction which is then translated to the solid B - no problem.
C - shows when the blend gap appears... you will see in the top view the only difference is that I have tapered the curve inwards, but by doing this you can no longer get the blends to meet up.
D - with this one i added some extra points to the curve and bingo it worked fine...
I'm guessing that blending is quite sensitive to the smoothness of the original line work that you draw.

All in all i've achieved what i wanted now and learnt quite a bit in the process, thank to all who have responded.

http://moi3d.com/forum/get_attachment.php?webtag=MOI&hash=6b0ece3447c8c0fbc9c0eb1d016d921b&filename=Test.3dm
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 From:  Barry-H
5491.20 
Hi Cube,
I have looked at your file and see that you are blending in sections.
If you run the Rebuild command on you profiles and set the tolerance to 0.001
you will be able to blend as one surface.
If you look at the photo attached you will see I have added another model (right view top model)
where I have adjusted the top curve as it was to close to the extruded outer profile at
the one end and when blended was causing a small bulge.
Hope this helps.
Barry.



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