point3d: Optimize vec3 → point3d initializer
point3d: Optimize vec3 → point3d initializer

We call this a fair amount; we can shave some time by avoiding the
single channel reads in favour of a single memcpy.

criptych/graphene,criptych/graphene,criptych/graphene,ebassi/graphene,criptych/graphene,ebassi/graphene