The Zen of Splines

[LurkerAbove]

It looks like when you weld control points Shift+Weld vs Weld (right click while holding the left mouse button on PC, or a ~ click on mac) the behaviors are different.

 

It looks like Welding the ends of a spline together joins the spline, making one spline, while Shift+weld seems to attach them, but they don't form one smooth spline.

 

 

Can someone point me to documentation that explains this better. The book also mentions something about spline direction, which I can't seem to find information about either.

 

I've looked at the basic splinesmanship web pages, and they are great, but also dated. Also, in an attempt to force me to do things rather than just see what's going on, the basic splinesmanship page sometimes gives instructions without a 'completed example'.

 

So what is the difference between using A and Shift A to add control points? When I do it, I don't see any difference on my model, but the tutorial indicates there is one, but *I'm never told what*.

 

Its maddening really. But I promise to read all documentation that I'm pointed to, and I will document any anecdotal knowledge so that this becomes easier for everyone. It seems like a lot of problems come down to splinesmanship, and I'd like to beef up our collective knowledge in this area, if I'm not the only one having trouble.

[Caroline]

Thank you for pointing out this difference to me. I've spent a lot of time just doodling with splines to get the feel for them, and adding an extra point to a spline I'm going to cross, so that I definitely don't join onto the same spline.

 

I looked in the Technical Reference manual for "Shift A" and came up with this that explains it:

http://www.hash.com/htmlHelp/v12.0/CustomHtml/Join.htm

 

So in summary, I think, if you have an existing spline with 2 points, and you start a new spline that is going to cross the existing spline, if you just A onto the existing spline, the new spline will become part of the existing one. But if you Shift A, then the new spline will be a second separate spline.

 

I find the Technical Reference Manual, which comes on the disk, often has useful snippets of knowledge. It is often frustrating, because you can't read it easily, but if you kinda sorta know what you're looking for, it is often there.

[LurkerAbove]

Thanks for the info. I'm on V13, and tried to search under Shift A and didn't seem to pull that up. It is helpful, though, and perhaps I need to dig into the older technical references.

its hard to use some of the older references though, because the interface has changed, and sometimes things are referred that don't exist.

 

I don't mean to gripe, just pointing out.

[Caroline]

I've learned a lot about searching in the last few months - even before learning splining, I think it's the most useful basic skill! And I enjoy searching, because I will always learn something on a totally unrelated topic that will be useful next week.

 

I've learned to put quotes ("") around everything that has a space, and in the forums, if I go to the search box on the main forum page, to search for separate words with a + sign in front of them, so you get both words in the search.

 

As for example I just looked for +spline +tutorial, checked the titles of the many threads, and came up with this thread, which is talking about the same sort of thing:

http://www.hash.com/forums/index.php?showtopic=23013&hl=

 

and this one, which is a wink tutorial about avoiding creases, but you're probably past this stage:

http://www.hash.com/forums/index.php?showtopic=13938

[LurkerAbove]

Those are helpful, and if you haven't found the basic splinemanship site yet, its well worth the read, and its fascinating. Great stuff, but it leaves me wanting to know more.

 

like, "What's Spline Direction?" Without a def, it sounds like left or right.

 

I'd love to actually do some animations or screenshots of spline concepts, about when they hook up and when they don't.

 

It does seem as though splines are the root of all evil

[Caroline]

I really enjoy modelling with splines - I'm making a huge (for me, anyway) model (the requisite newbie dragonish creature), and I really like being able to pull out a few points and adjust the shape of his tum, or add a few points and make the top of his head more lumpy.

 

The challenge now is to look at my model and remove unnecessary splines. Some of the models out there are so elegant and spline-light.

 

I think one of the tutorials that really helped me suddenly realize that I'm working in 3d space, but I hesitate to mention it, because it is 10 years old, and the decal bit at the end doesn't apply, is this Skylark one by Jeff Lew:

 

http://www.hash.com/users/jsherwood/tutes/SkyLark.pdf

 

And to keep it on-topic, it shows building a flat face, and adding extra points so that it's obvious where to hang other splines. It's not as good as Colin's Cooper face, because I don't think that Jeff had 5 point patches way back then, but making a flat face and pulling out the features is a very different approach.

 

But if you can put together the definitive "what to do with splines, how to avoid creases, how to add new splines, how to get rid of existing ones", then you'll definitely be approaching enlightenment.

[LurkerAbove]

That one I haven't seen. Its a pretty slick tutorial. I think the idea of pulling out the features is kind of neat as well, and cooper was put on a shelf for another day.

 

The A:M handbook has Martin's face, of all things, and tries to explain things about hooks and 5 point patches, it comes after the quintessential dinosaur example, which I'm very excited to try.

[robcat2075]

That Skylark tut is a classic.

 

Anyway, I believe "spline direction" refers to how splines "meet". More often called "spline continuity" .

 

[attachmentid=22665]

 

 

Crossing GOOD... bouncing off each other BAD.

 

They can appear the same, especially if they are peaked at the meeting point. But the bad way is really bad.

[LurkerAbove]

That Skylark tut is a classic.

 

Anyway, I believe "spline direction" refers to how splines "meet". More often called "spline continuity" .

 

[attachmentid=22665]

 

 

Crossing GOOD... bouncing off each other BAD.

 

They can appear the same, especially if they are peaked at the meeting point. But the bad way is really bad.

 

 

Thanks for clearing some of that up. I have a vague notion why the GOOD is indeed GOOD. Can you help me understand why BAD is BAD?

[robcat2075]

I have a vague notion why the GOOD is indeed GOOD. Can you help me understand why BAD is BAD?

 

Guess which intersection is BAD...

 

[attachmentid=22667]

 

bad spline continuity causes creases and weird shading artifacts .

 

Splines like to cross like an X. they don't like to bounce off each other like two parentheses )(

 

the basic splinesmanship pages are still solid advice. can you point to an example that didn't seem right ?

[LurkerAbove]

I have a vague notion why the GOOD is indeed GOOD. Can you help me understand why BAD is BAD?

 

Guess which intersection is BAD...

 

[attachmentid=22667]

 

bad spline continuity causes creases and weird shading artifacts .

 

Splines like to cross like an X. they don't like to bounce off each other like two parentheses )(

 

the basic splinesmanship pages are still solid advice. can you point to an example that didn't seem right ?

 

Thanks for the illustration. Here's an attempt at one of my own:

 

 

[attachmentid=22668]

 

When the red and goldenrod splines were the same spline, I got weird artifacts. It was only after I shft-attached did it work like I wanted it to.

 

As to what didn't seem right, I probably mis-wrote. Here's what I read on the basic splinesmanship page:

 

Make the "A" and "B" splines again on a different part of the screen, this time for

spline "B" you can use the "Add Lock Mode (shift +A) Button" and directly draw

a spline with 3 CPs on it. Now, grab the center CP on spline "B" and move and

weld it to the end of spline "A." Notice the difference in the resulting shape. I'm

not showing a picture here so that you have to look on your own screen. Pretty

tricky huh.... ;-)

 

Unfortunately, I didn't see anything cool or tricky. Using Add Lock didn't seem to be different than using just plain old add. Sadly enough, I still don't know the difference between them.

[robcat2075]

 

 

Unfortunately, I didn't see anything cool or tricky. Using Add Lock didn't seem to be different than using just plain old add. Sadly enough, I still don't know the difference between them.

 

Ok, that part was out of date. Add-lock behavior is the normal default mode of the Add tool now. The old simple Add just drew 2 CPs and stopped... I think.

[LurkerAbove]

Thanks so much for clearing that up. I know that keeping up with documentation is hard, and the basic splinesmanship tutorials still rock on toast, but its moments like that which make the veins in my head throb.

[someawfulbridge]

Something I learned from the beautiful, beautiful David Rogers book:

 

Shift-A adds a control point to the preexisting spline WITHOUT reshaping the preexisting spline.

 

As far as adding to the preexisting spline, that's going to depend on which spline is selected when you add a control point. If you're welding to a CP in the middle of a spline, you're continuing your new spline and just "passing through" the CP. If you're welding to an endpoint, chances are you'll be adding the new spline to the old.

 

Make sense? I know, I know, I'm just a neophyte, but discovering the wonders of Shift-A was a wonderful thing.

 

Mark

 

Thanks so much for clearing that up. I know that keeping up with documentation is hard, and the basic splinesmanship tutorials still rock on toast, but its moments like that which make the veins in my head throb.

[LurkerAbove]

Shift-A is a beautiful thing to know. I can't wait to try this out. This and Y (which adds a control point to a selected spline) are great tools to have.

[robcat2075]

Shift-A adds a control point to the preexisting spline WITHOUT reshaping the preexisting spline.

 

you really mean holding shift while you click on a spline while in add mode , right ?

 

just pressing shift-a couldn't possibly know where to put the new CP.

[LurkerAbove]

Great question. I'm not sure. I want to try it out.

 

I also punted and got the Rogers book. Let there be knowledge!

[C-grid]

Maybe good advise to you:

 

There's a textfile called tips.txt in your Hash A:M directory.

When you add all your 'own' tips, you have a fast look-up and you can delete 'the now obvious'-stuff.

[LurkerAbove]

Thanks for mentioning the file C, but I'm not sure why I would use that instead of something like the wiki (althought it doesn't seem community editable) or using the helpful links here.

 

One advantage I see with using the links and adding such online is because the tips added online are more community accessible.

 

Am I missing something?

[C-grid]

Aha, I don't have internet at home...

[LurkerAbove]

That would do it. I see your point.

[C-grid]

Another usage could be having your own per project 'tips' (and have them available during the different opened scenes, p.a. character-descriptions).

[someawfulbridge]

Shift-A adds a control point to the preexisting spline WITHOUT reshaping the preexisting spline.

 

you really mean holding shift while you click on a spline while in add mode , right ?

 

just pressing shift-a couldn't possibly know where to put the new CP.

 

 

D'oh! You're right. This is what happens when I try to act all smart and stuff and things.

[LurkerAbove]

Another usage could be having your own per project 'tips' (and have them available during the different opened scenes, p.a. character-descriptions).

 

Could you elaborate on this?

[C-grid]

Well, if you were making a StarTrek-like series, you could place StarTrek-lingo in the tips.txt, and/or the rememberance of particular keyframe-durations for specifics, you name it.