Skeleton Chain on a Curve

[I3D]

Hey Everyone

It has been many years, so SI memory is not as it used to be.

I am trying to animate a tank treads for a game vehicle. The game engine I am using doesn't take shape animation, only bone deformations and transformations. So I wanted to animated the tank treads using bones following a closed curve path. For the love of me I cannot remember how it was done, and google search resulted in nothing. It is a similar technique I guess to the a snake on a path like this: or like which both were done in Maya.

Can anyone share any pointers on how to accomplish this in SI? The model that I am trying to animate is similar to this one: viewtopic.php?f=25&t=7083

Please don't mention blender or Houdini. I don't want to spend whatever free time I have learning a new software just to animate a tank treads

Thank you

[opoppopopp]

Not fully understand what you want.

Key point of the snake video, from rigging perspective, is "Slide on curve" Nulls(Bone, deformer, whatever)

But what you want is just Tank thread right.
Why not just "path constraint" your Envelop deformoer which will eventually in your engine, and set some "Expression" on the Path %age parameter ?
And plot the animation before export to your engine.

P.S. for "Nulls sliding on curve", for a short answer, take look at that "StudioNEST Brigks Rigging Toolset", on this sites Resources section
There is a specific "curve slide" solver Script Op.

2021-03-20-05-43-58.gif

[I3D]

Hi opoppopopp

Thanks for your reply.

The object (i.e. tank treads) is not a multiple objects, but a single object. This is the model actually: https://skfb.ly/6UDVM.

My current setup is that I've rebuilt the object flat and added a 2D skeleton chain to it. and I want to slide the bones over the curve using the path percentage of course.



In your example, each tread is sperate, placed on different positions on the path and linked to the cube x position. This I can do, it will require me to change the object slightly. I'm only wondering if I have an enveloped objects, can I conform the bones to follow the curve shape? In the Maya example with the Snake. The snake is an envelope character and the whole chain is manipulated using a spline/curve.

I'll have a look at "StudioNEST Brigks Rigging Toolset", thanks for the tip.

[opoppopopp]

Hi opoppopopp
...bones to follow the curve ...

Why not just envelop your mesh to bunch of Nulls, Envelop OP don't care what your deform object is, It is only calculate positions.

Or you have other specific reason for must use bone chain.
Technically "Bone Chain" is only an legacy concept, It is no more than bunch of parented Nulls, with an IK sovler, etc.

Or Why not direct "Deform by Curve" of your poly?

A simple script will be enough for constrain your skeleton to curve
but in that way, you have to make your chain "stretchable" to fit curve length, make it "translate along curve", what ever, at that time, you don't take any advantage of using a Skeleton in first place...

2021-03-21-01-58-11.gif

[I3D]

Hi opoppopopp

Thanks again for the clarification. Sorry, but I still don't get. I tried to deform the enveloped mesh but getting wrong results. Please note that I haven't used XSI for many years now, and honestly It's starting to come back slowly. Would it be possible to share the scene you have showing with me?

Thank you

[opoppopopp]

Hi opoppopopp

Thanks again for the clarification. Sorry, but I still don't get. I tried to deform the enveloped mesh but getting wrong results. Please note that I haven't used XSI for many years now, and honestly It's starting to come back slowly. Would it be possible to share the scene you have showing with me?

Thank you

a bunch of nulls slide on curve, poly enveloped to those nulls, nothing fancy...
Already PM you a scn file

[I3D]

Thanks heaps opoppopopp, got the file. really appreciate it.

Cheers

[opoppopopp]

Thanks heaps opoppopopp, got the file. really appreciate it.

Cheers

Hope your problem solved.