model like ASM (active shape model) [closed]

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I want to use model like ASM(active shape model) for face recognition.

For example I mark by the hands points on 1st image and 2nd and then I want to compare them.

What metric I should choose?

My 1st assumption was to use simple euclidean distanse for 2D points, but before I need to "align" models for example calculate сetres of gravity and align, and then apply scale changes,also I can align by the axes of the ellipses, but I think it doesn't give good align results, I think I need some non linear cost function to "morph" from 1 model to another.