if the product has no head morph, but it has full body morph,
you can take out only head shape morph from full body morph.
I tried same things before by editing obj file directly, but there was more good way.
As Richard said, if you have good 3d tool, you can do it easy.
if you use Blender , you can do it by “shape key” and Blend from shape key.
you can copy vertices of head node only and use it as new morph.
I tried and tested it before.
but if you have only hexagon (as you know it is free good 3d modelor now)
you can spilit only head morph from full body morph too.
but you may need some steps to spilit it about hexagon.
eg Faerie is one of character morph in monster morph sets. but the character has not head part morph.
and not ear morph too,,. but I made them from Farie full body morph by hexagon and morph loder pro.
(though you may need to smooth around neck (joint part) in hexagon,,the head shape is perfect same )
if you really hope to know how to make it,, I can tell you ,,
but need many steps. (not difficult but need careful work to keep vertex order, )
you may need to understand how to use morph loader pro with reverse option too.
but As Richard said, you may need to adjust rig for the new shape, and ERC freeze,
for expression or pozing, and need to reshape around joint part (neck part) in hexagon..
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