I have built my spine joints and I want to add Follow Curve operator. As Houdini usual workflow suggest, it would be normaly done opposite - first create curve, than let Houdini generate number of bones. But I need my bones to have specific lenght each because most of the movement occurs at lumbar area, less movement in the thoracic area. That`s why I don`t want to let Houdini to generate bones automaticly.

I tried to create the connection myself, creating InverseKin and filling in all necesary objects (start joint, end joint and path), but it didn`t work. The bones don`t move when I moved curve points.

Any advice?

I`m using Maya as a rigger, but now I`m taking a look at Houdini too, because it`s more supported and it looks like it`s system works better.

meanwhile I was bit experimenting. I found some way around. bones can be first generated by BonesFromCurve and then repositioned by Bones tool. FollowCurve operator is snapping bones always back to curve (which is ok), but it remembers the edit of lenght by Bones tool.

if the bone structure for the whole character is done first, the spine could be created proceduraly, creating curve along bones positions (like in Maya), creating the same number of bones and repositioning them based on the original bones (which then would be replaced by new BonesFromCurve created bones roughly matching their positions).
Obviously with all children (arms, neck…) unparented and then reparented back again preserving positions.

You didn't mention if you also manually filled out the Kinematic Solver parameter on each bone to point to your InverseKin CHOP.

Hi Syntetik,

If you want to build a spine proceduraly take a look at the bodypart spine asset or open the attached, simplified file.

Here is a short description of what I'm doing.
Once you have a set of bones on the curve you can change their length to match your preference, shorter in the lumbar region big one in the thorax.
So first define the curve and create a ik with the number of bones. By default their length will be constant.
Then create a bunch of controls on the curve using the path object.
There is a handle that allows you to move the controls on the curve, you access it with “y”.
Bind the bone length to the distance between 2 handles. In the bodypart spine I'm running a script that does that because I want to do it at the rigging stage.

Back to the example file:
select a null press y and move the handle which will adjust the bone length.

cheers
calin

edward
You didn't mention if you also manually filled out the Kinematic Solver parameter on each bone to point to your InverseKin CHOP.

Hello Edward. yes I didn`t fill the KIN solver… :roll: But my friend who is much more exprienced showed me that and he also showed me that InverseKin can have Export turned on, which is also the way to activate it.
Or by using Add Kinematics with Bones tool (I guess).

So that was cool that I can create FollowCurve kinematics on existing bones.

calin_casian cheers for the advice. procedural rigs is my hobby and job in Maya, so it`s nice to see some stuff like that in Houdini. I`ve opened your file and it looks nice and clean.
I`m new to Houdini. Right now I`m also interested in basic stuff like gimbal lock and rotate order. Houdini rigging works slightly different than Maya and I want to find out if it`s worth to do character animation in it, rather than Maya.
My main reason why I started looking at it was integrated muscles/sliding skin. Than I found other nice things about seting up advanced rigging pipeline.

syntetik
he also showed me that InverseKin can have Export turned on, which is also the way to activate it.

Yep, that's the old school way of doing things. The only disadvantage with this method though is that you can't do IK/FK blending anymore since the the InverseKin CHOP is now controlling the bones via the FK rotate values.