Fuselage help please

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 From:  Noob
7366.1 
Hello.

I am a total noobie with MOI and I really love it. I am trying to model a velocity v-twin plane. i wanted to try to model it in MOI as a first project to get comfortable with it. I'm having problems with the fuselage.

I've watched a number of Andrei's youtube videos...which are helpful, but i am a little confused with what i'm doing wrong. I've spend a lot of time trying to get my curves just right. i've tried network but after watching Andrei's videos i'm pretty sure that loft is the best technique to accomplish what i want and get the best topology in the end. I'm using MOI pretty much with the out of the box setup and i haven't setup any plugins or shortcuts, which Andrei uses.

Question 1:
There are a few things I'm not sure how to 'fix' after a curve has been drawn. For example, say i wanted to adjust the roof of the fuselage cockpit area and give it a slight arc like in the references after i've created the initial curves and still keep the center point/curves tangent to the center line? or adjust curve points and make them tangent after the initial curve has been drawn?

Question 2:
I'm not sure if i'm going about cutting the curves into the fuselage to separate the surface is the 'right' way. after i create curves from the right orthographic view, i project the curves onto the surface that i will intersect with the surface to make a separate surface for the windows. first, i'm not sure if this is the 'right' way to do this, and secondly, the curves are not being projected completely onto the surface...the bottom pieces on the back windows are not projected. i have checked the original curve to make sure all the joints are actually connected. so i'm guessing it may have something to do with the surface edge that is conflicting with the projected curve, since they appear to be either in the same spot or close to it. any advice?

Question 3:
Let's say I figure out how to resolve questions 1 & 2 above, what is the best approach to think about bevels? should i think about them before i project any curves and do a copy/offset on them first, then project? or can i do a bevel later once i get my base created for things to then work on beveling things that need beveling?

I appreciate any help or advice...thank you!! I really love this software, it is very intuitive, i am just wanting to get familiar with it and figure out how to approach things in general so that I can make cooler things :)

~ NOOB






Project curves...this happens (bottom lines are not projected from original curves):



Velocity v-twin plane (see 'image attachments' for some plane references)

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 From:  Michael Gibson
7366.2 In reply to 7366.1 
Hi, welcome to the forum and to MoI!

An airplane is one of the more difficult and advanced projects that you could really try to do in a CAD program, it may be awkward for you to start out initially with such an difficult level of project rather than doing something like mechanical parts to get familiar with things to start with... Just something to be aware of. The more that your design uses organic flowing shapes the more it can be better suited for creating in a sub-d modeling program rather than in a profile curve driven CAD program like MoI.

quote:

There are a few things I'm not sure how to 'fix' after a curve has been drawn. For example, say i wanted to adjust the roof of the fuselage cockpit area and give it a slight arc like in the references after i've created the initial curves and still keep the center point/curves tangent to the center line? or adjust curve points and make them tangent after the initial curve has been drawn?


You'd turn on the control points for your curves, and edit those points to move the appropriate ones upwards, keeping the last 2 ending points of the curve to be in a horizontal line to control the end tangent direction.

If you want to make adjustments it can help to try and use a smaller number of curves rather than a lot of curves.


quote:

Question 2:
I'm not sure if i'm going about cutting the curves into the fuselage to separate the surface is the 'right' way. after i create curves from the right orthographic view, i project the curves onto the surface that i will intersect with the surface to make a separate surface for the windows. first, i'm not sure if this is the 'right' way to do this, and secondly, the curves are not being projected completely onto the surface...the bottom pieces on the back windows are not projected. i have checked the original curve to make sure all the joints are actually connected. so i'm guessing it may have something to do with the surface edge that is conflicting with the projected curve, since they appear to be either in the same spot or close to it. any advice?


For answering this question it would help a lot if you could post the 3DM model file in it with your geometry, so I could inspect it and try to repeat the trim over here and see what's going on. It's a lot easier to analyze the actual geometry than it is just a screenshot. One general note though, you don't need to project curves onto the surface as a separate step, you can just cut using the 2D curves directly and let Trim handle the projection for you, which is the preferred way.

quote:

Let's say I figure out how to resolve questions 1 & 2 above, what is the best approach to think about bevels? should i think about them before i project any curves and do a copy/offset on them first, then project? or can i do a bevel later once i get my base created for things to then work on beveling things that need beveling?


Well it depends on what particular pieces you are going to be beveling. For a complex shape like you've working on there you will probably be looking at using the Construct > Blend command to put in smooth connecting pieces between things rather than the Fillet command though.

If you can post your 3DM I can give you some better information probably...

- Michael
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 From:  Noob
7366.3 In reply to 7366.2 
Thank you for taking the time Michael! I really appreciate the help and advise.

I've attached the last version i have w/out the projected curves for the windows.

~ Noob

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 From:  Frenchy Pilou (PILOU)
7366.4 In reply to 7366.3 
you can have measures inside Free DesignSparks ;)
http://moi3d.com/forum/index.php?webtag=MOI&msg=6186.1

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 From:  Michael Gibson
7366.5 In reply to 7366.3 
Hi Noob - so one thing that would probably help with manipulating shapes would be to use fewer curves, right now your current setup is rather dense with cross sections and the more sections you put in the more constrained the shape will be and it becomes easy to have bumps and undulations in the shape.

Another thing that can help is to use the "Loft style = Loose" option which will tend to make a more relaxed surface. With that option the surface will only be guided through the cross sections and not go exactly through them, so your cross sections need to be a little larger than the final shape for that mode. You can also include a point object (draw it in under Draw curve > More > pt) at the front and back to make your loft closed, that works best with Loft style = Loose as well.

For your trimming, one complication is that one of the internal edges of your loft just barely skims right along the same bottom line of your trimming curves. You can still trim with that, but it's possible the Trim command may get confused in the step where it asks you to pick which pieces to discard, you may have to just push "Done" there and then select the faces after that and use delete if you want to get rid of them.

You may possibly want to run the Rebuild command on your loft cross sections before lofting them to make those curves to be just one single smooth curve rather than a segmented curve. Info on Rebuild here: http://moi3d.com/3.0/docs/moi_command_reference10.htm#rebuild


.... After a bit more investigation it looks like there is some bad shaping near the back of the shape where the surface is kind of strained and probably zig-zags back and forth over itself, creating a self-intersection. Self-intersections in a surface will cause problems with intersection and cutting operations so that's probably what is really messing up the Trim in your case here. Here's a screenshot:






Maybe try running the Rebuild command on your cross-sections to eliminate the segmentation in them and make them made up of just one smooth curve segment, that will avoid the compression that is happening currently since one of the segments in the end section is very small I guess.

Hope this helps!

- Michael

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 From:  kevjon
7366.6 
If you reduce the amount of fuselage cross sections used you can get a reasonable result with network-normal or lighter.

The trick with network is to use as few cross section curves as you can to define the shape and let the perimeter curves do most of the work.

You will need to experiment with amount of curves and their placement to get something that is good enough for your purposes.

EDITED: 25 Apr 2015 by KEVJON

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 From:  Mauro (M-DYNAMICS)
7366.7 
Hi Noob:take a look at this,maybe can help you even if speaker's language is not clear :)

https://vimeo.com/65707052
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 From:  Frenchy Pilou (PILOU)
7366.8 
Excellent! Can I put your tuto videos on my site ?
By Mauro ;)


EDITED: 26 Apr 2015 by PILOU

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 From:  Mauro (M-DYNAMICS)
7366.9 In reply to 7366.8 
Yes of course...sorry for language,i tried to do my best :)
This is the link to the gallery:
http://moi3d.com/gallery/viewitem.php?id=614
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 From:  Frenchy Pilou (PILOU)
7366.10 In reply to 7366.9 
Spiegazioni sono perfetti !
Done! ;)
http://moiscript.weebly.com/avion.html
---
Pilou
Is beautiful that please without concept!
My Gallery
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 From:  Noob
7366.11 
Thanks for all the help!!!

The P-38 Lightning videos are going to help out a LOT!!! GRAZIE MILLE MAURO!!!

i will post the progress...and/or other problems/mistakes i make :) ...since everyone is so helpful here (which is very refreshing)...reminds me of the zbrushcentral forums.

thanks again...michael, frenchy (big fan), kevjon (thanks!), and mauro!

eventually i'm hoping to change my username here :)...you gotta start somewhere right?

~ Noob
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 From:  Noob
7366.12 
Ok, so its been a few days and i've run into some issues with this fuselage. i ended up cleaning up the points on the rails and profiles to make the geometry lighter...and i'm pretty happy with the results....except for the part on the top of the nose. i've re-made this quite a few times and tried to refine the profiles and i'm not really sure why it seems to be bulging when it should be a linear arc towards the point of the nose and roof.

is there a way to fix this after the surface has been generated? (within MOI) or some other technique to generate the fuselage w/out the bumps?

i really didn't notice it until i started to try to cut things out of the fuselage...so i started over...from the base network and the bulge is there as well..so i don't think it was the cuts.

thanks for all the help!

-noob

here are some screenshots and keyshot renders to show what i'm talking about (different iterations)











EDITED: 2 May 2015 by NOOB

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 From:  Noob
7366.13 
I opened up the file in Rhino (mac) just to see. (i don't really know how to use rhino.). ignore the wing :)

it looks like the geometry is bunching up in those areas. any ideas?






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 From:  Michael Gibson
7366.14 In reply to 7366.12 
Hi Noob,

> is there a way to fix this after the surface has been generated? (within MOI) or some
> other technique to generate the fuselage w/out the bumps?

It's very difficult to give any good advice just looking at screenshots, it's a lot better to post a 3DM model file with the actual geometry in it.

It tends to be difficult to alter things like this after the surface has been generated, usually it's better to address such things early on in the surface creation process.

For a more relaxed surface you might try using Loft with the Loft style = "Loose" option, that tends to make a relaxed surface.

The other thing that would help is to avoid having profile curves that have harsh transitions in them like totally straight line segments switching into suddenly curved portions. Later on when things try to fit a smooth surface to something like that it will have difficulty making a smooth transition from totally flat to suddenly curved. If your profiles were made up of more gradually changing curves rather than lines and arcs that would probably help too.

- Michael
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 From:  Noob
7366.15 
Hey everyone,

I wanted to post some keyshot renders of my progress on the v-twin plane...there are a lot of errors in this that i need to fix, but this is what i have so far.

Michael, I decided to just go with what i started because I didn't have enough time to figure out a better way to do the fuselage...or at least a better way to get some cleaner geometry. I really appreciate the help and advice! Gotta lot to learn definitely.

-noob








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 From:  Michael Gibson
7366.16 In reply to 7366.15 
Hi noob, it's coming along well!

- Michael
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