I have noticed when a group of meshes with textures & faces fairly close, that setting
hasAlpha = true causes clipping for a PBR material, while not for a STD material. Here is a side by side:
Which vertex “wins” varies, based on camera angle. Here is the head when scalp is winning:
I verified the problem by setting
hasAlpha = false manually. Things are no longer spastic, but notice the eye browse & lower edge of the hair are not right.
The glTF exporter must be setting everything to false, because nothing shows through, but still also has problems where textures actually have alpha not pegged to 1.