Ik-spline not updating via geometry-shape

Support Animation and Rigging
1

hello,
I don’t know what to do,
I have a chain that has a spline-ik on curve (A).
Curve A gets the shape of curve B via geometry nodes.
(I need a dynamic shapekey!, only a shape that looks like B will not work!)
Unfortunately, when I fade/blend curve A to B, the chain does not go with it.

image
image2437×1267 246 KB

I don’t know whether this is a limitation in the geometry node or whether it works after all.

Even with an Empty-obj it is not updated,

thanks in Advance

geometry_node_shape_for_IK-SPLINE.blend (1007.2 KB)

2

As far as I know this is a limitation. I ran into it last year too. The entire constraint system (including splineIK, follow path…) seems to disregard the evaluated curve when it is modified with geonodes. I honestly don’t have a workaround to give you, sorry.

1 Like
3

Oh what a pity, I am at least happy that i can control the shapes with geomtry-nodes, let’s see when the rigging comes in there too.

Thanks anyway and good to know that you noticed it too

4

i would recommend using animation nodes for that. That works “normally”. I often switch to AN because GN cannot do some sort of things.

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5

Thank you,
I’m not a beginner, but I think my head would explode immediately,
I would need a part that works already in geometry nodes, that would be completely new to me.
I will try a different concept with the blender tools.

6

While you can’t have GN “act on spline” the same way other curve modifiers do, for accessing them via spline IK, you can use your GN curve to position vertices that are assigned to various vertex groups; you can then use other kinds of constraints to track these positions, marked with VGs:

image
image1563×1148 233 KB

geometry_node_shape_for_IK-SPLINE1.blend (1.0 MB)

3 Likes
7

it’s not really complicated.

You can use this node tree here:

change spline ik on the fly

All you “really” have to change is your spline IK target to “Target” and then it should work.

As you can see, it works very similar to GN but with a lot more possibilities. Mix vector does the exactly same as in GN, but AN also provides handle + position information via one node as you can see. Then a new spline will be created by “spline from points” which is self explaining.

But yes, you have to install “animation nodes” - which is a free add-on (built by one of the GN developers :wink:

an - spline ik moved via an.blend (1022.3 KB)

2 Likes
8

Hello Grandmaster Bandages,
fantastic and thank you very much.
That’s how it should be and it helps me a lot.

One question about the objeckt “Plane” , was it originally a plane and you changed it in edit-mode so that it becomes the spline ?

9

Yes ,
indeed, it looks very clear and comprehensible,
many thanks for the example,
will continue with GN for now because the rig should work for several upcoming Blender versions .(Knock on wood!)

10

Yeah. I wanted a string of verts, that represented the rest positions of your bones. There’s no “string” primitive so I just made a plane, deleted two points, subdivided the remaining edge.

11

thanks for the info.
I wasn’t sure at first whether this might also be generated in the GN.
then everything is clear now .

:raised_hands:

12

Can’t generate the geometry inside of GN, or it won’t have VGs. When you use generated geometry, any attributes are only stored as attributes, not readable by constraints. (If you have base geo, you can assign VGs in GN-- it’s just generated geo that won’t work. I just assigned the VGs to the base geo, but it’s something you can do.)

13

I suspected you might come in with a workaround, haha
Nice one, thanks !

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