Nsided Patch Problem - V3 Aug 1

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 From:  kevjon
6120.1 
Hi Michael

I tried out nsided patch to create a wing fillet for an aircraft. It wasn't too successful.

It would make this task really easy if I could get it to work. Your insight would be appreciated.
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 From:  bemfarmer
6120.2 In reply to 6120.1 
For the larger pink object, why is there a space between the upper edge curve, and the pink surface?
The upper top of the pink surface looks like it is made up of line segments.
Or is this just a display artifact?
-Brian

Raising "Point Count U" to 200 greatly reduces the problem areas?

EDITED: 14 Aug 2013 by BEMFARMER

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 From:  Mauro (M-DYNAMICS)
6120.3 
Hi Kev:
alternative solution:

make a BLEND G2 (bulge=0,5) between two main edges



extract ISOCURVES from blend surface



delete now blend surface than select isocurves+ four original edges and hit NETWORK choosing CUSTOM to have tight tolerance



now you have a Patch where main edges are G2 connected (NSIDED give just G1)

it's a compromise..i know...but you can't expect that tools work in all situations..this is a complex case (i attached my file)

M

EDITED: 29 Jan 2015 by M-DYNAMICS


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 From:  Michael Gibson
6120.4 In reply to 6120.1 
Hi Kevin, the way N-sided patch works is by making a kind of star pattern connecting edges to a central hub point - it won't work well in cases where the edges do not form a generally convex boundary like in your case here.

Also it gives a kind of equal weight to each edge and that can make a mixture of significantly different length edges to be a problem also.

If you set Bulge = 0.1 and Point count U = 100, you'll get a result that is not as mangled but still has a pretty significant downward swoop in the middle area from the influence of the lower side edge. In the future I'd like to see about being able to set the central point directly which may then help for cases like this where the auto generated central point is too low or high for the desired result.

- Michael
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 From:  kevjon
6120.5 
@Michael

Thanks for the explanation and the tips about increasing the spans for smoother results. Moving the point sounds like it would be a useful addition to the tool.

@Mauro

Cheers, looks like a really nice solution and final result. I have noted that Michael has significantly improved Network over the 1 & 2 versions of MoI.

Just one question. How do you know when to use Lighter for Network or Custom ?
When using Network->custom how do you know what figures to type in the input box ?

@bemfarmer

Thanks for the tips about increasing span for smoother results. While it didn't work in this instance the tip may help when I use it for other things.
~Kevin~
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 From:  Mauro (M-DYNAMICS)
6120.6 In reply to 6120.5 
Have a try with this surface using NORMAL-LIGHTER-CUSTOM
after each choice turn on control points:you'll see different densities and "topology"
supposing you want to move some surface's points,you can choose option that give less control points (easier to select and manage)
you also can see little curvature difference between LIGHTER and CUSTOM...choose option that fits better your target
Network try to build a shape following curves you draw,often make a compromise, giving unwanted bulges
I noticed choosing CUSTOM you force Network to follow your curves with a tight tolerance avoiding to go beyond them
This is fundamental when later you'll join the patch with fuselage and wing
Sorry for my English and for this explanation,maybe is not 100% correct
Let Michael,if not too busy, talk about different Network choices

M
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 From:  Michael Gibson
6120.7 In reply to 6120.6 
Some information on the new Network choices:
quote:

Updated Network command - fixed a bug that was causing Network results to be extra lumpy in certain circumstances, the fix should give better quality surfaces. There is also a new "Mode" option that you can adjust to modify the fitting behavior.
Mode = "Normal" fits the boundary curves by the regular fitting tolerance. This makes the resulting surface hug the shape of the boundary curves accurately enough so that it can be joined to other things built off of those same curves.
Mode = "Lighter" makes the surface fit to a looser tolerance, making a lighter surface but that adheres less to the boundary curves.
Mode = "Custom" - allows you to enter in a numeric tolerance value of your own choosing.
Mode = "Uniform" - allows you to enter in a number of points - each section of the Network is fit with that number of control points per region rather than refining things adaptively to meet a distance tolerance like the other modes.
You can use one of the other modes than "Normal" if you want to output a less constrained and lighter surface at the expense of it not hugging as tightly to the boundary curves. So one thing to note if you use Network is that there is now an additional stage to the command where you can set the mode, and the command will not complete until you push "Done" or right click on that new additional step.


- Michael
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 From:  Mauro (M-DYNAMICS)
6120.8 In reply to 6120.7 
Thanks Michael !
Before last update i noticed choosing CUSTOM with default tolerance (0,01mm) allowed Network to follow exactly boundary curves
That's why i choosed immediately CUSTOM with Kevjon's patch....but now i know i can choose NORMAL thanks to this update
anyway...leaving apart my approximative explanation (in English).... i understood right :)
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 From:  Michael Gibson
6120.9 In reply to 6120.8 
Hi Mauro, so some additional specific details:

"Normal" mode actually uses the default relative tolerance (0.001 if your object is between 1 and 50 units in size, otherwise a fraction of the curve's bounding box size) for the outer boundary curves and 10 times that amount for the tolerance of the interior curves.

"Lighter" mode uses boundary tolerance of 15 times default tolerance for outer boundaries and 30 times default tolerance for inner boundaries.

"Custom" mode uses the value you set for both boundary and inner fitting tolerance.

"Uniform" mode uses the given number of sample points rather than doing a tolerance deviation based fitting.


Also if you are doing a 4-sided network with no interior curves, there is also an "Exact" setting available that uses the curves as-is (inheriting all curve structures into the result surface) with no refitting done at all.

- Michael
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 From:  kevjon
6120.10 
Thanks all, very useful information about the Network command in v3.

Having lots of trouble patching the wing/fuselage joint on the underside of the aircraft and making it all look smooth and seamless. So for now I head back to polygon modelling but will keep on eye on future development of MoI to see if tools become available that will solve problem areas like these.

EDITED: 16 Aug 2013 by KEVJON

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 From:  Mauro (M-DYNAMICS)
6120.11 In reply to 6120.10 
Forgive me Kevjon but i think it not depends by futures Moi's tools to solve your trouble
I mean you should consider a different approach to model that plane
Why split the fuselage in half ? You'll have the seam..difficult to join smoothly
Why that wide hole underside if the fuselage shape there, is not flat but curved?
Take a look at side wiew i highlighted with red arrows..you should model the whole fuselage with Loft or Network, following the jellow line i highlighted,THAN..trim fuselage and do the blend to join the wings
or..after whole fuselage,start to draw a wing section to trim fuselage than follow Samardac Method:copy first section and paste scaling them when needed to do the Loft...now you have also close to point option ;)



hope you'll understand what i mean

M

EDITED: 16 Aug 2013 by M-DYNAMICS

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 From:  kevjon
6120.12 
Hi Mauro
The aircraft is P39Q Aircobra.
I've tried many different ways than the one posted to get a smooth transition between the wing and fuselage and try to make it look close to the real thing.


> Why split the fuselage in half ? You'll have the seam..difficult to join smoothly

The fuselage is modelled as a whole following Samardac loft method except I used (normal-exact). I've just split it in half to to simplify the task of patching this area. Whether you are patching the whole area or just half, the issue is the same ?


> Why that wide hole underside if the fuselage shape there, is not flat but curved?
> Take a look at side view I highlighted with red arrows..you should model the whole fuselage with Loft or Network, following the yellow line I highlighted,THAN..trim fuselage and do the blend to join the wings

The bottom of the fuselage needs to follow the contours of the underside of the wing, it doesn't have the bottom of the fuselage projecting through the contours except at the front and rear of the wing.


>or..after whole fuselage,start to draw a wing section to trim fuselage than follow Samardac Method:copy first section and paste scaling them when needed to do the Loft...now you have also close to
> point option ;)
> I have tried this way except the real aircraft does not have the contours of the fuselage projecting through underside of the wing. The fuselage shape instead flows smoothly into the contours of the wing >undersurface.

I'm really excited about the Samardac loose loft method & loft to point, however it doesn't allow seamless transition of two surfaces in two directions like patch or network.
I have attached the curves of the wing and fuselage if you could show me a nice way of getting the two to flow smoothly together on the underside of the wing would be greatly appreciated. I think it might be good learning exercise for others as well.

EDITED: 17 Aug 2013 by KEVJON


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 From:  argo
6120.13 In reply to 6120.12 
Wish you luck with this kevjon,
I hope you find a solution as it is similar to the fin/fuselage challenge I had (unsolved) in the ...Organic Modelling of Glider Fuselage topic I started.
Cheers.
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 From:  kevjon
6120.14 
@Argo

Thanks

I don't know if this helps you but this is how I tackled the fin/fuselage joint. I used Network and blend.
Actually thinking about this more, I could probably get rid of the network and included that part in the loft of the fin shape.

I also tried Andrei's Loft-Loose-Exact for the whole fin including the fuselage fairing but it doesn't give tangency at the fuselage joint which results in undesirable shading highlights when converted to polygons and rendered. It really needs to be at least G1 blend to overcome the shading highlight errors.

EDITED: 17 Aug 2013 by KEVJON

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 From:  Mauro (M-DYNAMICS)
6120.15 In reply to 6120.14 
This is just to explore alternative ways :)
You could try to mirror wing sections and loft whole wing than move some points of yellow section until you have a better shape





my suggestion is also to pay attention how to manage points in wing sections
supposing you need to blend wing+fuselage surely it failed because wing is too sharp
avoid also to have the seam of the wing just in the sharpest part
use MarkCurveStart plug-in to control each section and move it in neutral position




red one is a section of your wing,blue one is how i managed points in that area:
avoid to put a point in the sharpest part,give more distance between them to have more rounded shape
this allows to blend or fillet to have more space available to work

M

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 From:  OSTexo
6120.16 
Hello,

Part of the issue may be that the edges and surfaces are causing more trouble due to the control point organization and complexity. After doing a few tests I've found you can get better surfaces by having less points that are placed well than more. It also may be harder since you are trying to create the entire surface in one piece. Perhaps some model planning would help so that you can create several smaller surfaces that exhibit good control point placement rather than trying to deal with one large surface. I don't think loft is going to get you where you want to be in this instance if you are looking for something past G1. Getting to at least G2 and having a nicely planned model should get alleviate some of the smoothing issues.
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 From:  kevjon
6120.17 
@Mauro

>You could try to mirror wing sections and loft whole wing than move some points of yellow section until you have a better shape

That looks like it has some potential combined with a blend between fuselage and wing. I'll give that a go and post up the result, good or bad.

>my suggestion is also to pay attention how to manage points in wing sections
>supposing you need to blend wing+fuselage surely it failed because wing is too sharp
>avoid also to have the seam of the wing just in the sharpest part
>use MarkCurveStart plug-in to control each section and move it in neutral position

The extra point you show in the red curve (which is the way I did it) is so I can snap my wing profiles to guides to avoid having a wobbly leading or trailing edge to the wing.



>avoid to put a point in the sharpest part,give more distance between them to have more rounded shape
>this allows to blend or fillet to have more space available to work

hmm, good point. Perhaps I need to delete my snapping point after I have all the wing cross sections in place. It may help when doing the blend between fuselage and wing.

This is the shape I need to create on the underside of my wing. As you can see it is relatively flat under the wing.



@OSTexo

I'm more than happy for you to show me how to achieve better results with a better planned model and less points.
~Kevin~

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 From:  kevjon
6120.18 In reply to 6120.17 
Ok, here is one way of tackling it. The white lines in the Network patches are G2 blend curves to try to keep continuity.

But after converting to polygons not too good.
~Kevin~
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 From:  kevjon
6120.19 
Ok, I think this is bit simpler and gives a result that is good enough for my purposes.

What I learned in this exercise should stand me in good stead for other low winged aircraft.
~Kevin~
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