Before revision:  Recently, two other algorithms were claimed to be constant-factor approximations for the c-packedness using axis-aligned cubes instead of disks, which only consider the vertices of the curve when determining the c-packedness and therefore contradict the original definition of the c-packedness that has no assumptions on the placement of the disks. Call this measure the relative c-packedness.
After revision:  Recently, two other algorithms were claimed to be constant-factor approximations for the c-packedness using axis-aligned cubes instead of disks, which only consider the vertices of the curve when determining the c-packedness . We call this measure the relative c-packedness.