alias support - an alpine helmet

Hello,


I’m working on a ski helmet for a project and realize I’m a bit rusty when it comes to Alias. If you could spare a few seconds to look at those images and give me some hints. I’d be the happiest boy on the planet!

This is the wirefram. I used a bi-rail using the three vertical lines as generic curves and the top and botton curves as rails. In the next step I wanted to mirror it and the following occured…


I understand that the surfaces aren’t tangent where they meet, but all the generic lines have a 90 degree angle from the centre line. What can be the problem?

I also wonder why there’s a gap between the two surfaces and, finally, if I can somehow do it as one surface instead of two?


Btw it’s Alias AutoStudio 11 and ImageStudio for renders, if that should be an important issue.


Thanks on advance,

First of all, you used blend curve, and I hate it.

Secondly, when you create the first side, make sure you choose “implied tangent” for that edge.

thirdly, if the implied tangent doesn’t work, you can create a flat surface perpendicular to the first surface and align tangent to it.

Generally speaking, for me, I don’t usually create half and mirror. I create a surface that covers the middle.

You hate blend curves, are there motives for that (such as performance) and, if so, what are the alternatives? I’ve only taken one class in Alias, was told that blend curves are the best and I never really argued.

The problem as I see it is that I need a shape that has to close in the top, in combination with the fact that the shape has to be “tall”, why I can’t use for example a serie of circles to sweep the surface.

What method would you suggest to create the shape?

It’s a personal preference. I use 5th degree curves if I want curvature continuity and align them to cos and get the exact curve that I am looking for.

Thank you for great help!


I think my problem here is that I haven’t understood how to deal with curvature continuity/tangency. Or, i know we did it during that class but it’s lost.

I suppose curvature continuity is applied on curves and not on surfaces? I don’t understand how to achieve tangency/curvature continuity between a 5th degree curve and a straight line, what tool to use? Sorry for real stupid qustion, and thanks again.

Hmmm… NURBs modelling is all about using curves to create the surface you want.

Rule:

Your curves have to be EXACTLY what you want before you can use them to generate surfaces.

That means you need to make sure the curves are tangent/curvature the way you want them before you can achieve a surface that has the same continuity.

To align your curves, use the object aligh tool.
Palette>Objects>Align

You can choose beteen positional, tangent and curvature.

First click chooses the curve that you want to change. Second click chooses the curve you want to be aligned to.

Definitions of the continity types:
Positional (G0): The end point or edge of curve/surface touches each other.
Tangent(G1): The end pt/edge of curve/surface meet to form a highlight without a controlled roll of.
Curvature (G2): Meet with controlled roll off and acceleration.

Tangent: Aligns the first CV to the tangent of the other curve/edge.
Curvature: aligns 2 cvs.

Therefore:
Tangent requires 2nd degree curve and above.
Curvature requires 3 or more degree curves. If you want to align on both ends, you need to use 5th degree curve.

To choose degree of curve, double click on the edit pt curve tool and make your choice.

After you get your curves set up and done right, you can surface them using square or birail tools. Make sure you turn on the continuity choice on the respective edges in the tool window(double click it).


Looks like your instructor hasn’t really taught anything, or that you slept your classes away. Really, these are the most fundamental concepts. If you are familar with these, you can build almost anything, Rhino or Alias.

See, this is why I hate blend curves. You learn to use it, but you don;t understand how it works.

The class was intensive and in Italian (not my cup of tea), but I’m quite sure this part didn’t exist.

Thank you very much for help and explenation, you’ve been of much help! I’ll post renders of the final design when it’s getting there.

Ì appreciate your help a lot! Though it gets even worse and it seems as the more time i spend in the program the more I forget. I have two additional questions if that’s OK?

In your first screencapture, you have placed two horisontal lines that both align to the XY plane. As soon as I start to place curves on a positive/negative to distance to the XY plane it keeps putting the controlpoints in the plane. How do I control that? I.e. how do I create a plane that aligns to XY and draw in it?

How do I make two 5th degree curves to intersect along the curves and not on their endpoints?

I don’t get what you mean, but perhaps you don’t know snap tools.

Snap to grid: Alt+mouse click
Snap to CVs: Ctrl+left mouse click

I didn’t show many things in the screen shots because I just wanted to show the method. I don’t know how much you know about the software.
The curve you see isn’t on the origin planes. They are above the XY plane. If you want to align A to B, you got to have B first right? So you have to create the curve or surface that you want your curves to align to. Or you can simple move CVs to the position you want.

Snap to CV in one dimension: Ctrl+middle or right mouse click, each aligns in a different dimension.

To snap along edges/curves, hold ctrl+alt and click on the curve/edge.

To intersect, meaning to cut curves, use the curve section tool ( under palette>curve edit>last button). First click chooses the curve section you want to keep. Second click chooses the cutting curve. This process is not reversible, so back up a curve first.

Looks like you need someone to show you how to do things. I don’t think you can finish your model with this amount of knowledge. It’s hard to show you without being there. Alias is not as dummy proof as Rhino. There are lot’s of things hidden and you won’t know until someone tells you. I’m still learning, but at least I can build things without those more advanced knowledge.

I still can try to answer your questions. I suggest you to sketch out what you are trying to achieve first and plan out the procedure. That will save you a lot of time.

Well, thanks to your comments I’ve achieved what you showed me above, using 5th degree curves, curvature continuity, construction planes, snapping, etc. Much appreciated! But i agree, it’s not very easy to self-learn the software, and the pdf help files are terrible…

A question, when I use Symmetry and import the modell in ImageStudio the symmetry-half doesn’t appear, any idea why?

I’m not -that- teerrible at Alias and I think it will work out, just need to put down some spare time in the project. I have some blueprints of previous helmets from the company that I will use as viewport images to achieve the correct shape…

Symmetry is just a rendering of the model, it doesn’t exist as a real surface.

Is there some way to transform a symmetry into a new surface, or should I use the duplicate function?

Ok, these are three images of the current situation, i think it’s getting there.



The surfaces with surface quality shader (or something)


Two renders. It’s another way of building up the modell but I Guess it works equally good?

If that’s the surface that you want, then it’s good. I can see some devations on the surfaces and I don’t know if they are intended.

An additional question; above I’ve used 5th degree curves from forehead to neck. The curves going from the top of the helmet in the ear’s direction are assembled of smaller curves, each one going between one forehead>neck curve.

Are there any curves/tools that I could use to create one single curve in that direction too? I want to create a grid that covers the head, which would make the final shaping of the helmet much easier…

Thank you

I don’t know if I understand you, but there are 2 kinds of curve tools.

Edit point curve and CV curves. You are using edit pt curves. If you want to get a long curve, try cv curves. They work differently, but may give you what you want.

You can also just continue to click with the edit point curve.

thought Id see how the surfacing is going and if you still need any guidance

You can create real geometry for symmetric layers (before you take your data into ImageStudio) by using the Layers->Symmetry->Create Geometry tool.