How To Make Bone Aim Always One Way (+y) Even If Father Rotates

[alberto-toglia]

Hi all,

I want to do a train like motion, or maybe an engine (same case) with joints. The thing is that I need a specific joint not to respond (with rotation) when its father rotates, like a loose joint or a mechanical bearing, and to point always to the same direction while respecting its inherit translation.

I have solved my issue with code but I didnt like that solution because I will export it to an fbx file, and I have faced problems using expresions..., and also I want to learn more about animation, rigging, joints and IK solvers.

I have tried everythig, locking almost every atribute, chaging its freedom axis, but nothing seems to get the joint to aim always to the +Y cord while its father is rotating.

I have left and image showing exactly what i need to do.

Thanks in advance.

[joojaa]

Well yes you can do this, with bones and a driven key but it wont export right trough the fbx pipe necessarily.

with code you do mean expressions right? What you basically wanted is a orient constrain wich would possibly work over fbx as perhaps a driven key too,

[alberto-toglia]

I got it solved unparenting joint3 from joint2 then adding a "parent contraint" without rotation inheritance ( Someone helped me out ), havent tried exporting it yet though, I hope it works...

I know it can be solved wih the aim constraint too, or the driven key like you say, the thing is I need it to work on the ".fbx", So I can use c# code (and xna framework) to rotate that joint and make the animation work, its for a train game...

If anybody has any idea how to manipulate joints on the xna framework I will be all ears. I know it can be done!

Thanks for your reply!

[joojaa]

Ahh, well i think your a bit over emphasizing the workload to your exporter. Odds are it wont work on fbx even whan it does your game eingne reader don't necessarily understand this, offcourse if its baked to keys it will work, but thenagain then it dont differ if you had a expression.

(becauise in effect thet would mean your game iengenes graph is equal to mayas)

[alberto-toglia]

So how do you think I can do this ? ...having all the bone structure in one piece so I can rotate it on runtime and have all the pieces moving toguether.

Thanks