6 (glide-reflections, translations and rotations) is generated by a glide reflection and a rotation about a point on the line of reflection. If that is all it contains, this type is frieze group p11g.Įxample pattern with this symmetry group:įrieze group nr. In the case of glide reflection symmetry, the symmetry group of an object contains a glide reflection, and hence the group generated by it. Ĭombining two equal glide reflections gives a pure translation with a translation vector that is twice that of the glide reflection, so the even powers of the glide reflection form a translation group. The isometry group generated by just a glide reflection is an infinite cyclic group. This isometry maps the x-axis to itself any other line which is parallel to the x-axis gets reflected in the x-axis, so this system of parallel lines is left invariant. These are the two kinds of indirect isometries in 2D.įor example, there is an isometry consisting of the reflection on the x-axis, followed by translation of one unit parallel to it. Thus the effect of a reflection combined with any translation is a glide reflection, with as special case just a reflection. However, a glide reflection cannot be reduced like that. The combination of a reflection in a line and a translation in a perpendicular direction is a reflection in a parallel line. ![]() It can also be given a Schoenflies notation as S 2∞, Coxeter notation as, and orbifold notation as ∞×. A glide reflection can be seen as a limiting rotoreflection, where the rotation becomes a translation. In group theory, the glide plane is classified as a type of opposite isometry of the Euclidean plane.Ī single glide is represented as frieze group p11g. ![]() The intermediate step between reflection and translation can look different from the starting configuration, so objects with glide symmetry are in general, not symmetrical under reflection alone. In 2-dimensional geometry, a glide reflection (or transflection) is a symmetry operation that consists of a reflection over a line and then translation along that line, combined into a single operation. Since this footprint trail has glide reflection symmetry, applying the operation of glide reflection will map each left footprint into a right footprint and each right footprint to a left footprint, leading to a final configuration which is indistinguishable from the original.
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