pb with GORDON surfaces  1-20  21-22

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 From:  lorem (LOREMBOLO)
1191.1 
Hi,

I must be stupid, cause I don't really understand Gordon surfaces...and the way it works..
:(
here is a chair I want to model. The lines are explicits to see the desired volume.



But I can't achieve to make a gordon surface with these splines....
Do you know how I must do ?

Thx in advance for help...

3dm scene attached
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 From:  Fitz (3DARTZ)
1191.2 In reply to 1191.1 
wouldnt you use the net surface tool?
then you could just shell it to get the thickness?

Mike Fitz
www.3dartz.com
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 From:  Marc (TELLIER)
1191.3 In reply to 1191.1 
Hi Lorem,

I have made an attempt to do a similar shape with network, (just an excuse to explore this command that I don't know very much :)


It seems that this shape is better done in two halves and mirrored afterwards...

Marc

EDITED: 10 Dec 2007 by TELLIER

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 From:  efra (EFRAIN_AMADO)
1191.4 In reply to 1191.1 
Hi Lorem,I found that selecting the curves and separete them you can choose one half and aply ofset,after is done you hide the curves so you can go with the other half good luck .enjoy.
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 From:  lorem (LOREMBOLO)
1191.5 In reply to 1191.4 
Many thanks to all of you guys !
I'm going to test the different methods...



Marc >>> I also made this model to explore the Gordon tool...it is still difficult to me...You get exactly the thing...

Efra >>> You mean offset tool with the main outilne curve divided in two ?

Fitz >>> The net surface ?? As I use french version, I'm not sure what tool it is.


Anyway, thanks again.
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 From:  efra (EFRAIN_AMADO)
1191.6 In reply to 1191.5 
Sorry Lorem ,my mistake. is network tool.
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 From:  Michael Gibson
1191.7 In reply to 1191.5 
Hi lorem - for the Network tool (this same tool is labeled "Gordon" in the French UI) to work, it needs to be able to determine a 2D grid layout for the curves.

Think of it as latitude and longitude lines on a world globe that correspond to horizontal or vertical lines on a flat map.

In order to provide this kind of organization, your single outside loop will need to be split into 2 pieces, so that you will have 3 long curves that touch at at 2 "pole" points at either end.

With that layout you can then see that the long curves will be like longitude lines on a map, and the shorter curves will be like latitude lines.

To split the long curve up, select it and run Edit / Trim, then select your center long curve as the cutting object.

After that then these curves have a suitable arrangement for Network. Except Network doesn't seem to behave properly with them still, that seems like it may be a bug in Network, I will take a look into that.

One other thing you can try right now would be to use Sweep instead - select the shorter curves as profiles, then run Construct / Sweep, then pick the 2 outside curves (the ones that were split from the long closed curve) as the rails.

- Michael
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 From:  lorem (LOREMBOLO)
1191.8 In reply to 1191.7 
Thx Michael,

I've found severall solutions.
But I would like to use the net/gordon tool for trainig purpose.
I started over from scratch, it works, but with the old file it seems ther is a pb....

I continue exploration....and post soon the different methods used

thx for helping !!
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 From:  lorem (LOREMBOLO)
1191.9 In reply to 1191.8 
I can't wait :)

So : my first method :


I have a question :
Why can't I use "Proj" intersection beetween main outline curve and solid at step2 to get separate volumes?
It only creates some points on the solid...that's why i use the "ugly" extrusion method at stpe3....

Not really good method to my opinion, but it works....
;)

Sorry for the bad english...
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 From:  Michael Gibson
1191.10 In reply to 1191.9 
Hi lorem,

> Why can't I use "Proj" intersection beetween main outline curve and solid at
> step2 to get separate volumes? It only creates some points on the solid...that's
> why i use the "ugly" extrusion method at stpe3....

You mean by using a Boolean command?

That won't work for your case because your shape is not a flat planar curve. For curves to interact with solids in the Boolean commands, the curve must be planar so that it has a well defined extrusion direction. Otherwise MoI is not able to figure out the extrusion direction.

If you use Edit / Trim it can work if your curve is pretty close to the surface - Trim will do a kind of "pull" on a non-planar curve towards the surface to be trimmed but it can get confused if the curve is not pretty close by the surface.

- Michael
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 From:  lorem (LOREMBOLO)
1191.11 In reply to 1191.10 
Thx Michael,

ok for boolean... I was thinking of this tool :


and it dont work...or I don't understand ;)
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 From:  Michael Gibson
1191.12 In reply to 1191.11 
Hi lorem - that tool is for something different, it will create the curves where 2 solids intersect each other.

It does not cut or edit the solids in any way, it only creates new curves, like this - 2 solids that are pushing through each other:



Calculation of the intersection curves - these can now be used as a rail curve or for other construction purposes:




This command can also be used to find the points of intersection between a curve and a surface or solid, like this:





But the key thing is that this command creates new objects at the curves or points of intersection, it does not cut or modify objects - to modify objects use Trim or the Boolean commands instead.

- Michael

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 From:  lorem (LOREMBOLO)
1191.13 In reply to 1191.12 
Ok, I understand...
So my method is not so "ugly"....
;)
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 From:  Frenchy Pilou (PILOU)
1191.14 
hi lorem
Something i don't understand : your curves are not "jointed" at the intersection and even not attach at the sides!!!
Is that normal?

Despite of that Gordon works fine :) Separate the entiere object; kill the half et voila :)
---
Pilou
Is beautiful that please without concept!
My Gallery

EDITED: 11 Dec 2007 by PILOU

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 From:  lorem (LOREMBOLO)
1191.15 In reply to 1191.14 
Yes Pilou, you are right.

In Help file, it's written about network : "It is not necessary for the curves to exactly intersect,"
But, if the Network tool works fine in the 3dm scene I first posted, it doesn't work anymore on my new scene....maybe too much attempts, and other tools used...so I start over a new one.

Question : is it a problem to make a network with different kind of curves (point surves and control points curves...) ?? ?

Note : the problem with the Network/gordon + Mirror method is the tangents...symetry is not perfect and it's a bit tricky to adjust points to achieve a perfect mirrored object... ....
+++
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 From:  Marc (TELLIER)
1191.16 In reply to 1191.15 
Hi lorem, you must already know this but it is relatively easy to make curves tangent with control points, you just align them in a perpendicular way. (see attached)

If your object is not perpendicular to a plane it gets trickier, but building reference geometry with object snap works well in this situation.


Regards,

Marc
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 From:  Michael Gibson
1191.17 In reply to 1191.15 
Hi lorem,

> Question : is it a problem to make a network with different kind of curves
> (point surves and control points curves...) ?? ?

Yes, you can mix together curves that were made using different commands.

- Michael
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 From:  lorem (LOREMBOLO)
1191.18 In reply to 1191.17 
Thx for help....

I'm going crazy with network tool....
Here is another 3dm scene....I tweaked curves in order to have a perfectly mirroring object..and now network tool have no result....
:(

I think I'll try a different method...
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 From:  Malc615 (MALC)
1191.19 In reply to 1191.18 
Hi Lorem

I have found that the Network tool can be quite temperamental.
You have to use trial and error sometimes to get a surface just right.
I have been fiddling with an Audi TT car for a couple of month's (almost done) and have had the same sort of problems as you have encountered. Tried hundreds of ways to do the front wing but eventually cracked it with trial and error.

I have had a go with your chair and I think this is what you are after.

Notice the outer shell is just a mirror of the original - but still keeping the split down the middle, that is importatant for it to work - and then I used the back spline to creat the curves, just touching, to get the right shape.

Keep on trying and you will succeed I am sure.

Best of luck.
Malc.
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 From:  Michael Gibson
1191.20 In reply to 1191.18 
Hi Lorem,

> Here is another 3dm scene....I tweaked curves in order to have a
> perfectly mirroring object..and now network tool have no result....

It looks like MoI is getting confused about how to organize the curves.

If you turn on control points for your small curves and drag their endpoints so that they are snapped right on to the longer ones, that will clear up the organization and Network will then succeed.

If you run into other problems with Network, try to align the ends of your curves more precisely snapped on to each other and that should help. I will see if I can tune this up so that it isn't necessary though.

You can also use sweep for situations like this with 2 longer guide curves - it can be less fussy about how things are arranged.



One other issue - even though you have tweaked your curve tangents you will still not have a perfectly mirroring object here. It will be perfectly mirroring right at those curves, but in other areas the cross-section will shift and torque around which gets in the way of perfect alignment. For example here is what the control points look like near the tip of the surface:



That shifting happens because Network is not only created off of those profile curves but also the other long curves as well, which do not have equal length and pinch together at the top.

For network it can be easiest to get a smooth object by doing the full object all at once instead of half.

There is a special "Maintain tangent" mode for sweep which can build a smooth mirrorable object, but right now it only works if all your profile curves are on parallel planes. It works by keeping all the control points along those same planes instead of shifting them along the rails which is what normally happens. I think I should be able to tune up this sweep mode in the future to handle situations like the one you posted here.

- Michael
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