Help with birail

[Nem]

can someone show me how to birail this particular part of a car? like CV placement etc cos i tried and it gets really really messy because this isnt a simple face like the door

[Nem]

and heres the image

[bernhard]

hello nem !

well, I´m working on the same like you do.
I´m still trieng to model a simply part from a car, a vehicle or an airplane, or something else.

And I use the technique with EP Curves, and than Birail 1,2 or 3.

I will contact you with the MSN.
Maybe we can talk about that - I have some ways how you can use the birail option.

bye for now,
bernhard

[NitroLiq]

It might be nice to post your solutions here as well so others can benefit from your knowledge.

[mtmckinley]

first, make sure the curves that are opposing each other (left and right, top and bottom) match each other's spans.

(also, when dealing with a 2 profile, 2 rail birail, you can get the same result with a Boundary.)

For a Birail 2 (having 2 profiles), make sure the ends of the 4 curves are all point snapped to each other. If the ends are not touching, it won't work.

Select the birail 2 tool. Select the to profiles, THEN select the 2 rails.

Should work.

The boundary function creates a practically identical surface. Like the birail, the ends have to be snapped together and you get better results if the opposing curves match spans. Then, simply select them in clockwise or counter clockwise order, and surfaces > boundary.

[bernhard]

hello !

well, sorry for my bad english. I´m experimenting and I used the wrong vocabulary - so, I don´t really have a solution , cause I have many problems to model an objekt with that technique.

I only want to tell, that I am testing this tool, and well, I can´t really good explain - so I thought I will contact via MSN.

lol; sorry, but a good tip:
there is a wonderful gnomon video showing you that technique. I think it is Modelling III - the GTR car.

bernhard

[bernhard]

Hello Nem, Hello Mike !

Well, I´ve tested it and build up the EV-Curves I could see from the car.

The problem seems to bee, that there are more than only 3 profiles. Okay, so I thought it shouldn´t bee no problem to use birail 3+ - well, but I have no clue, why the birail doesn´t take effect ?


here is the PLE-Version file to download:
http://www.tophunter.at/3dproblems/birail_problem_nem.mp

I´ve tried 2 variants:
1st: selected the left ep curve, than the right one -->enter
than I´ve selected the rest


2nd: selected the upper line at first, than the lowest-->enter
than I´ve selected the rest

hmm, grrrr - no surface was built

mike, what do I wrong ?

thx,
bernhard

[Nem]

well this is what i get with birail 2

[adldesigner]

Could you post a wireframe?

[Nem]

here ya go

[mtmckinley]

looks like you just need to arrange your curves a bit. The 4th point on one curve will try to match the 4th point on the opposite curve (for example).

[Nem]

how many CVs would you recommend i use? cos it seems to get heavy no matter how many i use

[adldesigner]

Why don´t you try making some curves on that same surface NEM?
You could actually try a loft on some rather refined curves on surface. Might help you out. Then you discard this one.

[bernhard]

Hello friends !

Below you can see the exisiting ep-curves from Nem´s image - and only with that curves it wasn´t possible for me to use the biral 3+ tool.

So I added again a new ep-curve and used birail 2.
than it worked, but the result I´ve got, are 2 surfaces.

Q1. Isn´t it possible to use the birail 3+ tool on the existing ep-curves from Nem you can see on this image ?

http://www.tophunter.at/3dproblems/birail_problem.jpg

Q2: How I can weld (connect) two nurbs-surfaces fluidly ?
Hmm, I mean, is it really necessary to connect different surfaces togehther, to avoid such problems you can see on the first mesh image from Nem ?


thx for helping friends,
bernhard

[adldesigner]

**UPDATED May 24th**

What you guys should strive for before trying to go for a NURBS car, is understand first how the curves work, familiarize with the surface tools, make some tests along and generally get a feel for NURBS modelling before attempting a complex surface as this one.

That said, let me give you some pointers on NURBS modelling which might come in handy:

Opossing Curves should always have the same spans.
To change spans on a Curve, use the Rebuild Curve Action.
Opossing Curves should always have the same direction.
To change direction on a Curve, use the Reverse Direction Action in the Curves Menu.
When picking try to follow either a clockwise, or a counter-clockwise pattern. Don´t go picking them on a random order, I just use curves surface direction for this.


The Birail tools are not meant to be used as flat surface generator, but instead are to be used to create surfaces in which you want to control the location of generated isoparms.
To use them effectively, you should keep the preceding points in mind, remember to have them connected, and know when to use the Enter key.
Birail1 makes use of three curves (One profile and two rails). It creates a surface that pretty much starts at the profile, and finishes at the end of the rails. To use it: Start the tool, pick the profile, then pick the rails.
Birail2 makes use of four curves (Two profiles and two rails). It creates a surface that sweeps from the first profile to the second along the rail ones. To use it: Start the tool, pick the two profiles, then pick the two rails.
Birail3+ makes use of as much curves as you specify (Three+ profiles and two rails). It creates a surface that sweeps from the first profile through all the profiles you pick along the rail ones. To use it: Start the tool, pick the first profile, then the second till you´ve picked all your profiles, press ENTER, and then pick the two rails.


For the surfaces you guys are attempting to make, I´d really use the Boundary tool instead. Remember Nurbs are 4-sided patches, and as such 4-curves represent the ideal way to construct them. If you take those pointers -and the ones above- in mind you won´t have much trouble working with the Boundary tool.

Again, I stress, work first with some surfaces, twist them, play with directions, rebuild them, change spans .. before attempting more complex surfaces and all. Believe me, you don´t want to see stitching in badly constructed surfaces.

As per your image bernhard, I´d say that does not qualify for a Birail operation, you´ll only get a poorly constructed surface. Build a four sided one, and just Boundary it together.
To stitch them together is a whole other business, however it takes the same exact pointers in mind.

Hope this helps guys.

[bernhard]

Hello adldesigner !

yep, you are right - it´s much better I´m testing the tool on an very easy object - I have to do more training sectioncs.

I will see what I will learn - your tips are really good to me.
Thank you for helping us,

bernhard