Why can't animation alignment be set to specific bones?

[visby]

First off I know nothing about about animation but this question has been bugging me so I was hoping someone could give me a basic answer.

 

When aligning two characters for an animations a central point on both characters seems to be used. When the scale off the two characters is different then some animations such as sex are off. It would seem to me that if the alignment for sex animations was based on the related parts, the pelvis bone of the skeletons in this case then the alignment should be correct even if the scales are different.

 

So do all animation alignments have to be based on one point of the model? Or can different points on the skeleton be used for alignment purposes?

[Alakbar]

Different points can be used or even switched in mid animation, but that all depends on what you're doing and what scripts are telling everything to do.  If the alignments are based on same sized NPC's, it will change when one is resized because the alignments used arn't the torso but something else - most probably (just guessing) they are using the NiNode (scene root) of the nif file.  Hope that helps