Constraining spline-handle movement?

[Rantin Al]

AFAIK, using the appropriate Cinema XY or Z locks is the only way, but remember that this will not retain the handle heading. ie, you cannot use this to extend the handle. Best to use the different viewports. If you don't want Z movement, use the Front Viewport.

The only modifier I know of is the using the Shift key to control a single handle.

Illustrator it certainly isn't but there are a couple of options for working with splines under Structure > Edit Spline where I suppose you could assign custom keystrokes for regularly used actions. The Hard & Soft Interpolations are my most often used.

Serious spline requirements are best done in Illustrator and imported to C4D.
Remember to save as version-8.ai or earlier.
Use the Alt-D keystroke to toggle the axis when working with splines.
Final tip is never touch the splines when in Perspective View.

HTH, Alan.

[Newstream]

Hey, thanks a ton for the tips Alan :thumbsup:

Pre-tweaking splines in Illustrator for extra control before bringing them into C4D is definitely good practice. Unfortunately I was stuck with "precision" modelling the frame of a chair where the rail spline was snaking its way all over the place in 3D space which pretty much ruled out Illustrator this time.

Anyways, one good tip deserves another. I've found SplinePointSelector (http://www.total3d.de/index.php?b=downs&wo=viewkat&kat=Coffee-Scripte) to be a real workflow gem in C4D, especially when assigning a keyboars shortcuts to its basic two functions.

Cheers / Alex
http://www.badtastic.com/misc/frame.jpg

[Rantin Al]

Hi Alex,

You can still do a lot of the precision work in Illustrator, even for the snaky chair.
Make a precision side elevation and bring it into C4D. You might have to do a bit of rotating to get the proper orientation as Illy files import on the XY plane. (I think)
You just need to add a couple of extra points to allow for the depth radii and re-align them in 3D space. Just place them obviously out of position for easy identification and selection in Cinema.

Select the relevant points to offset, align the extra depth points, jump to the top view and move them appropriately.
Add any extra cross braces.
Mirror and Connect then sweep and admire.

Yes, JackMcRip makes some handy tools.
Cheers, Alan.

[Newstream]

Hi Alex,

You can still do a lot of the precision work in Illustrator, even for the snaky chair.
Make a precision side elevation and bring it into C4D. You might have to do a bit of rotating to get the proper orientation as Illy files import on the XY plane. (I think)
You just need to add a couple of extra points to allow for the depth radii and re-align them in 3D space. Just place them obviously out of position for easy identification and selection in Cinema.

Select the relevant points to offset, align the extra depth points, jump to the top view and move them appropriately.
Add any extra cross braces.
Mirror and Connect then sweep and admire.

Yes, JackMcRip makes some handy tools.
Cheers, Alan.

Thanks Alan,:thumbsup:
I've approx 23 more chairs to model and by the looks of it, a truckload of snaky chair-tubing to wade through so I'll definitely have another crack at that Illy-technique.
Cheers /Alex

[Per-Anders]

for chairs like that i'd actually start out by just modeling them with linear splines, then once the basic shape is there use the cinema chamfer command to smooth out whatever points i wanted to be smoothed (by however much), it woudl be much faster than trying to manually control the handles as you're doing (should take about 5 minutes or less per chair at the most to do the way i'm suggesting).

[Newstream]

Well, actually I used the Liner Spline tool to get the basic lines in place and then softened them using the Chamfer selected splines tool, simply eye-balling the background photo-reverence in the view-port.

There was only one tiny spot (the middle of the backrest) where the shape needed some tightening by pulling in the handles. That's when the absence of a Shift-key movement constrain of the handles a la' After Effects, PhotoShop & Illustartor became apparent.

/ Alex

[Darter]

Here’s a COFFEE expression for constraining spline tangents either horizontally or vertically. User Data are on the COFFEE tag.

If another point selected while using the expression, the active constraint will be automatically deactivated to avoid accidental resetting of the non-target point’s tangent. However, the constraint will also be deactivated when using Undo. This is due to Undo resetting global variables and I’ll be fixing this in an updated version.

Apart from this, the expression seems to be working okay but any feedback or suggestions would be welcome. If there’s enough interest I might have a go at creating a plugin tag.

EDIT: File updated.

[Newstream]

Here’s a COFFEE expression for constraining spline tangents either horizontally or vertically. User Data are on the COFFEE tag.

If another point selected while using the expression, the active constraint will be automatically deactivated to avoid accidental resetting of the non-target point’s tangent. However, the constraint will also be deactivated when using Undo. This is due to Undo resetting global variables and I’ll be fixing this in an updated version.

Apart from this, the expression seems to be working okay but any feedback or suggestions would be welcome. If there’s enough interest I might have a go at creating a plugin tag.

Ooohh...:bounce:

Gotta try this out when I come home from work.
Thanks Darter. This is most generous of you.
This is one of those smile-inducing workflow gems that one wishes were in the app from day one. One would think that tangent-handle movement restriction would be a no-brainer in a program where spline tweaking was concerned but obviously not.
Thanks again!

Alex

[PresNevins]

That looks to be very handy, thanks!:thumbsup: (I've really gotta take a look at what COFFEE can do one of these days...)

Pres

[Darter]

Ooohh...:bounce:

Gotta try this out when I come home from work.
Thanks Darter. This is most generous of you.
This is one of those smile-inducing workflow gems that one wishes were in the app from day one. One would think that tangent-handle movement restriction would be a no-brainer in a program where spline tweaking was concerned but obviously not.
Thanks again!

Alex

Thanks for the feedback, I'll be interested to hear how you go with it.

With this expression I had in mind keeping the move tool unconstrained while working on constrained tangents. It also enables tangents to be quickly snapped to a vertical or horizontal alignment.

At the moment, the tangent point positions are mirrored but I intend to add an option for unequal tangent lengths along the constrained axis. It would also be nice to be able to set this axis to any angle...

[Newstream]

Hiya Darter!

You ought to have a look at the Align to Vector Tool (AVT) (http://www.defcon-x.de/wordpress/c4d-plugins/) plugin for some ideas and inspiration because in a way it accomplishes something similar but with geometry points instead. The whole idea of aligning handles according to vectors or certain predetermined lines makes sense, especially when precision is concerned. This stuff isn't new, Programs like Rhino have had this level of control for years but there's a problem importing Rhino curves (that's what they call them in there) into C4D as splines. It can of course be done via Illustrator but unfortunately all 3D data is lost on the way.

Just a tip and my 2 cents.

Cheers / Alex

[Newstream]

Ok, so I've tried it and well...... I LOVE IT !
Darter, you have no idea how much this little nugget you've created is helping me out right now. I'm modelling a truckload of different chairs under a crazy deadline and the ease of pulling one handle and not having to worry or mess with the other side of the X-axis is bliss.

http://www.badtastic.com/misc/spline.jpg

Respect & Thanks Man! :thumbsup:

/ Alex

[heathivan]

Here’s a COFFEE expression for constraining spline tangents...
This is Awesome! Thanks so much for filling in the gaps on the spline control and sharing your work with us! ***This would be a Great Plug-In ***
(i do agree that this shoulda been core from day one too, Badtastic.)

---h

[Darter]

Thanks for the feedback guys, I wasn't sure how useful this was.

Badtastic, thanks also for the link to Align to Vector, this is a very useful tool which I hadn't seen.

I've updated the expression to allow creation of unequal tangent lengths with the Shift key. I'm adding a few other features but this is taking longer than expected so I'll put it up as is for now. The file in my previous post has been updated.

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