-----Original Message----- From: Thorsten Wilms [mailto:t_w_@...123...] Sent: Tuesday, August 31, 2010 15:01
On Tue, 2010-08-31 at 12:32 +0200, J.B.C.Engelen@...1578... wrote:
Just to get the math right (from what I understand of it).
- For P1, the skew is essential, because P1 does not allow
rotation symmetries, nor (glide) reflections.
When you make it a square, it becomes a member of p4m. (note that square or rectangle makes a difference)
I don't understand how P1 with a square becomes a member of P4M at all.
The following only fill the plane with square prototypes: P4, P4G. Not sure if I should make the others non-square because of that.
Sorry for the confusion. The confusion arose because I was thinking about a featureless square; because the other squares have a feature drawn in them to make them assymetric for rotations and reflections. You are right, P1 does not require the skew. (now I would almost write, "of course")
-Johan