initFromPoints
Initializes the given #graphene_plane_t using the 3 provided co-planar points.
The winding order is counter-clockwise, and determines which direction the normal vector will point.
Return
the initialized plane
Since
1.2
Parameters
a
a #graphene_point3d_t
b
a #graphene_point3d_t
c
a #graphene_point3d_t