How to model a screws, bolts etc.

[Arlekin]

Hello,

So I find myself having trouble with modeling screws/bolts. I have done the cork-screw tutorial etc but I cant modify this technique to suit my needs.

Lets say I have modeled an 8 sided bolt with no screws on it a smooth bolt.
How do I add consistent screws to it? And if I should decide do lengthen or shorten the bolt how to keep the screws intact and logical?

I have tried:

To extrude a > shape extrusion along curve's, lofting, revolve and twist but cant quite make it to work.

I could:

^^^^ revolve this shape and it would give me a pretty nice fake screw but I want a real screw shape.

Any advice is appreciated :dont know

[Arlekin]

Ah obviously the question is about XSI. I am using 2011 version at the moment if it matters at all.
Ah also these are my first posts in these forums so Hello everybody nice to be amongst you.

[Arlekin]

This is what I have but this is a positive triangular screw and its not merged to the bolt. So I am interested in how to do the same thing but to the bolt I have or how to merge them so that the V shape is screwed into the bolt (out of bolt's surface).

http://dl.dropbox.com/u/8166977/screw.PNG

[Arlekin]

Best i could do at the moment is this....

http://dl.dropbox.com/u/8166977/screw2.png

The problem with this is that it is composed of 2 different objects (if its a problem) and it seems to bog down my machine abit for some reason.
(Core i7 920 with 12GB's of DDR3).

[Arlekin]

allright this is 1 object but Im still not totally satisfied with it as it took way longer than I would have liked. It took so long because I had trouble with transitioning from the end of the spiral/screw to the tip and bolthead. I still think there is a better way of doing it. But not to seem dumb and useless I post my efforts.

http://dl.dropbox.com/u/8166977/screw3.PNG

http://dl.dropbox.com/u/8166977/screw4.PNG

[chrisg]

Hi Arlekin,

We can't see your images, as they are in your secure drop-box account.

[Arlekin]

Ah indeed, sorry about the images, it should work now and you should be able to see my progress this far.
Well actually pumpmapped or displacement map is a valid technique aswell. Initially I was thinking about modeled version only but now im interested in every possible way. I think I have managed to get quite ok results, let me know what do you think.

[Arlekin]

Yeap for a bolt I would flatten it, it somehow just happened as I tested it actually a flat end would have been simpler for me to-do. The main question was how to create a screw/bolthead from 1 geometry I actually suspect that the only trouble I had with this one was also because I used 3 sided screw and turned it into 6 sided bolthead had I used 4 sided shape for creating the screw/spiral it would have been easier/quicker had to battle few n-gons at the transition.

[Arlekin]

Also this brings me to another question, a while back I was asked to model a realistic plane/planes and i might still continue with this project but modelling a realistic propeller proved to be a real nightmare, I could get somewhat realistic outcomes but nothing I would consider perfect. The problem is they are not linear in the way they twist. I figured it could be done with twist modifier but it only "screwed" things up so I did it by hand but again I think there is a better way. I tried to modify the twist modifier on a curve graph. Anyways what I want/need is something like this:

http://dl.dropbox.com/u/8166977/03_short184.jpg

[Arlekin]

What I was actually able to accomplish:

http://dl.dropbox.com/u/8166977/short%207%20a.jpg

I am at the moment only asking about the propeller but actually the whole project was a nightmare, because there are no surviving planes and the schematics are unreliable.
Anyway propeller is something that still bugs me a little but where it really stopped me in my tracks was texturing.
It was supposed to run in a virtual booth where you can rotate the whole model and should be reasonably low poly so it wont kill the booths cpu.
What I couldnt do is to figure out how to properly UV map it and include all the lighting etc info into it.

P.S: How good is covnversion between 3ds and XSI currently? With this plane they wanted 3ds files and I managed to convert the basic geometry but is there a reliable way of modeling doing everything in XSI and then porting it into 3ds and having it work afterwards? I figure there should be as they are both owned by Autodesk now.

[Arlekin]

I would think that the hardest parts were: Tail-fin (had odd shape and it was very hard to get it to look right), radiator grille behind the propeller (has very nice jugend (art noveau)/industrial drop-shaped holes there that were also somewhat hard to get to look right).
Also as I mentioned before texturing/uv-mapping was the real stopping-stone.
If all the textures/materials have to be included into 1 UV/texture map then I found it very hard to figure out how to unwrap it in a simple meaningful way.
So that It would be easy to update decals etc later on if I needed or someone else needed.
The model should also be good enough for some basic rigging/animating (probeller turning/tailfin twisting etc).
In essence it was modeled/or should have been modeled for use in a very primitive low poly game.
I think Im gonna give it another try as there are 20+ such planes to be modeled for a museum exhibition and I would really like to learn/master the art of packaging the whole thing in a neat usable way.

Still the issue remains that they like to work in 3ds but I dont...so I would have to find a way for easy conversion.