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## Alias General

Contributor
Posts: 14
Registered: ‎07-13-2005
Message 1 of 8 (409 Views)

# How to build two surfaces of one 1-span surface with history?

409 Views, 7 Replies
05-10-2012 09:03 AM

I have one large surface (with history) then empty space and on the other side two smaller surfaces (three actually, also with history).

What I want to do is to able to build different freeform blends from the two smaller surfaces partially onto the larger one.

I said freeform blend because there cannot be any support curves between the surfaces, and I would like to see how G3 continuity looks.

The real reason behind wanting to do this is that I want to tweak all surfaces on either side to align nicely with one another, while looking at the curvature of the blend between them. That's why I need history, and that's why I don't want any support curved aligned in between.

So, the real question, I guess, is how can I split a larger surface, or the edge of a larger surface, into more than one, while still being able to retain history and enabling more than one surface to be built off that edge?

Mentor
Posts: 241
Registered: ‎10-05-2009
Message 2 of 8 (401 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-10-2012 02:02 PM in reply to: eobet

Hello,

So, u have one set of surfaces on one side, a gap, and a set of surfaces on the other side.

Now u bridge both sets of surfaces with a freeform blend.... So far so good.

Now, if u tweak any of those surface sets on either side of the blend, the blend will update accordingly, because the blend has construction history... So what is the problem?

If u have one surface on one side and 2 or 3 on the other, u can still blend.

If u prefer to divide the big surface on on side so that u have the same number of surfaces on both sides, u can use the detach command.

NOW, it s obvious  this comand cannot have history, because u divided the big surface into 2... so the big surface doesnt exist anymore.... So you want these divided surfaces to have history with what? There is nothing for it to have history.

I m not sure i know what you want..... Anyway, just let me know if there is something you didnt understand, or if i didnt really answer what u were looking for.

Bye!

Contributor
Posts: 14
Registered: ‎07-13-2005
Message 3 of 8 (395 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-11-2012 05:40 AM in reply to: ravenzep

I realize now that my description was quite confusing. I was a bit too much into what I was doing, I think.

The second part of your answer is what I was getting at.

And the detach solution is exactly my problem, because I do wish to retain history.

I thought there would be some sort of command, like "patch precision" for example, where one would get lines drawn across a surface which would be recognized by other tools as an edge to build from, much like I can use those same lines produced by the patch precision tool to align curves with.

But I guess that is going to have to be my solution. Curves aligned with patch precision hull lines.

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Posts: 241
Registered: ‎10-05-2009
Message 4 of 8 (392 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-11-2012 08:48 AM in reply to: eobet

Hi,

And you dont really need patch precision lines....Not a lot of control, really.

Just project a simple line wherever u want in surface and align to tha COS.

I never use patch precision lines.

Contributor
Posts: 14
Registered: ‎07-13-2005
Message 5 of 8 (390 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-11-2012 03:58 PM in reply to: ravenzep

I would strongly disagree with you there.

A patch precision line always has the same amount of degree and spans as the surface itself, and will never break.

A curve on surface, however, can both break if you edit the surface too much (loose contact with the edge, that is) and has an unecessary amount of complexity (and it's a bitch to edit).

I think even Autodesk recognizes that curves on surfaces suck, since they made them almost obsolete with the 2012 curve fit option.

Mentor
Posts: 241
Registered: ‎10-05-2009
Message 6 of 8 (383 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-12-2012 03:47 AM in reply to: eobet

Great. It s from disagreement that ideas are born.

Now let s go to the nitty gritty,

I strongly think you did not understand.

I just used a projection curve as a little example. Maybe patch precision lines have a better use for quickly creating sub-surfaces from surface iso-parametric curves, huh?

"A patch precision line always has the same amount of degree and spans as the surface itself, and will never break."

Yeah.... But this is not the point. Anyway a ISOPARM is the same thing, and is wherever you want it to be on a surface, unlike a patch line, which is on the surface at regular intervals, meaning it will hardly be on a position you want, it is imposed by the software.... That s why i say it gives you not a lot of control. You can have a isoparm anywhere on a surface, and a patch precision line . NO you cannot.

"A curve on surface, however, can both break if you edit the surface too much (loose contact with the edge, that is) and has an unecessary amount of complexity (and it's a bitch to edit)."

No, it does not, beacuse you dont do the curve that you are projecting on the edges. This curve should be extended past the edges, precisely for not breaking. Anyway, it was just a example, because after i align something to a COS i delete the COS. Secondarily. both COS and patch lines are not needed to align curves to surfaces , because there is a project tangent tool that does it, and on any direction you want. A patch line forces you to U and V directions only. No control  once again.

"I think even Autodesk recognizes that curves on surfaces suck, since they made them almost obsolete with the 2012 curve fit option."

Are you kidding me? LOL

COS are raw data, and are very important and needed because is the most approximated thing there is with a zero deviation, as should be expected. COS are not needed to really model things from them, but they very very important for other things. You know, when you align anything by projection (surfaces), the software is always using COS behind the scenes for that alignment.

They are not obsolete and never will be, because they are extremely important and needed. OMG man, dont say that to anyone....LOL

The curve fit option is for other things, and is only an approximation curve, and is not a new feature at all. Been around for many years, and is now optimized with a single algorythm.

Really i just meant anyway that a precision line generally is not lying where we need them.....For that we have isoparms and total control! Anyone has his own preferences of course.

A COS obsolete?....Ewww....for how long do you know nurbs? 2005? or 3 months really?

You shouldnt express such assertive opinions, about things you clearly dont master. Nurbs and alias, is clearly one of those things, as you have demonstrated.

Contributor
Posts: 14
Registered: ‎07-13-2005
Message 7 of 8 (378 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-13-2012 03:48 AM in reply to: ravenzep

If you delete a COS after aligning to it, you break history, and that doesn't work for me since I want help modifying both surfaces I want to join using history to see how to best position them before I add a proper blending surface in between.

Also, I thought the project tangent tool was made obsolete with the new align tools in 2012 as well?

Patch Precision can be 1 or 100 without affecting the actual surface, so that implicitly is some control on their position. And the U and V direction restriction is fine by me, because I find that the way to get highlights to flow best is to try to have the hulls flow in the same direction... but I guess that might be just me not being very good at aligning surfaces.

Regarding COS, perhaps you will understand my perspective more if I tell you that I'm originally a Solidworks user. That means that I don't care about nurbs or whatever underlying algorithm or behind the scenes calculations the software does. I'm a user, not an engineer, so why should I care? What I care is what the UI enables me to do, and Alias makes it very, very difficult for me to work with COS, so naturally I think they suck.

Then again, I also think that the clutch in cars is one of the stupidest inventions ever, because I just want to drive. Why should I care what gear the engine is in while I accelerate? It exposes an unnecessary inner working of the engine that I as a user have absolutely zero interest in. Just give me automatic and I'll be on my way.

I like the discussion too, but I'm sorry to say that you so far haven't convinced me that there is a better way.

Valued Contributor
Posts: 60
Registered: ‎01-26-2010
Message 8 of 8 (364 Views)

# Re: How to build two surfaces of one 1-span surface with history?

05-16-2012 10:22 PM in reply to: eobet

If you are using 2013, it is simple. In the Freeform Blend option box is a button called "Modify Range" which gives you sliders to adjust the start and finish points for the blend surface. This has been needed!

If you are using an older version, you can projetc a curve on surface where you want the Freeform Blend to end, trim the surface, create the blend and then untrim the surface. The blend will remember the trim. This works fine unless you are using Edge Align, in which case it works sometimes. This also allows you to move the curve you used to create the COS and therefore adjust the endpoint of your Freeform Blend. This will maintain all the surfaces history.

If you try this method but want to be able to use the Edge Align and it is not working, let me know and I can tell you a more complex method.

Don't hate on the COS's, they are necessary and gennerally a good tool. Most things can not easily be made without them.

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