check for inversion of triangles when snapping
check for inversion of triangles when snapping

yangf4/core,YetAnotherMinion/core,yangf4/core,YetAnotherMinion/core,YetAnotherMinion/core,YetAnotherMinion/core,yangf4/core,yangf4/core,YetAnotherMinion/core,yangf4/core