I'm putting some prelimary thought into an animation system I plan to implement and I'm wondering what direction people around here have gone as far as using either bones or tags. (To me a bone (or joint) is just a transformation matrix like in any standard animation system that vertices can index to and a tag is _very_ similar, however isn't exported along with a model but is defined externally through a text file). For example, lets say I want to attach a single thruster effect to a point on a space ship model. I have two choices; add the bone to the model and re-export it, or I could just add the tag as a child of the model root and attach to that. It seems like it would be annoying to always have to ask an artist to re-export if I'm tweaking the thruster position, but then again, perhaps the only time I'd be doing this is if the model changed anyways (so maybe it was better off in an artists hands). Has anyone run into these practicality issues or is it just not a big deal. The reason I ask is I'd hate to have to waste time supporting both if just using bones is sufficient. Thanks for any insight.

If the location of the thruster doesn't affect the art, then it seems reasonable to do that. If it does affect the art, then you have only made the problem worse.

A better idea is to allow a tag to specify a joint name as its base position and orientation, rather than fixing it to the root.

'Course this can bloat your animation data (since a joint name/reference lookup needs to be included).

Winterdyne: I was just giving an example in the case of the ship. Normally tags would be able to attach to any bone, not just the root model/world.

Wudan: Yes, interesting point. Originally I hadn't really considered the possibility of seperating the model and skeleton but perhaps that might make things much easier. In that situation I suppose it wouldn't be a far stretch to have a tag file as well since what I'm really striving for is a streamlined production pipeline where I'm not waiting a few hours for an artist to move a bone 0.002 units over, wasting his and my time in the process.

I gave it some thought though and it seems something like a tag is somewhat redundant if you're able to easily change your bones, so I might just concentrate my efforts more on that.

Thanks guys.