The orientation of edges of the cube, often only EO (edge orientation). An edge is considered oriented if it can be solved using only <L,R,U,D,F2,B2>. Methods such as Roux (6 edges), ZZ (all edges), and Petrus (7 edges) include this as a substep. Other puzzles such as the Square-1 have EO as a common substep (EO on a Square-1 is more precisely a separation of edges to the correct layers but it is always referred to as edge orientation.)
EO on multiple axes
On 3x3x3, there are three different axis EO can be done from:
- x axis
- y axis
- z axis
2-axis EO means that EO is performed on two axes by firstly orienting all edges on one axis and then on a different one by separating the edges that belong into the slice which goes through all faces of the EOs using only R, U, L and D moves. In the case of a Green/Blue front and Red/Orange front EO, this would mean that all E-slice edges (the E-slice is the only slice that goes through the green, orange, blue and red faces) are put into the E-slice, but not necessarily solved. This allows the edges to be solved <U, D, F2, L2, B2, R2>-gen and is used in Domino Reduction.
3-axis EO means that EO is performed on three axes by separating all edges into their respective slices after 2-axis EO <U, D, F2, L2, B2, R2>-gen. This allows the edges to be solved using only half turns and is used in Half Turn Reduction.
Edge orientation in Petrus is generally solved with the 2x2x3 block in the back with only R, U, L and F moves. A more detailed explanation can be found in #See also.
If an LSE edge has the sticker with the color of the U face or the D face facing up or down, it is good/oriented. Therefore, if that sticker is not facing up or down, the edge is bad/unoriented.
The bad edges can be oriented with only M and U moves. The solver usually tries to reduce the EO case to an "arrow" where only four bad edges remain, one in the D layer and the other three in the U layer. This is done because the arrow can be solved with the simple trigger M(') U(') M(') (the exact algorithm depends on the angle). For a more detailed explanation, follow the links in #See also.
Looking at the edges on the U face, D face, F face of the E-slice, and B face of the E-slice:
- If the sticker has L/R color it's a bad edge.
- If the sticker has F/B color, look at the sticker on the other side of the edge.
- * If the side sticker has U/D color, it's a bad edge.
Orienting 2 Bad Edges
Place one bad edge on F/B using <R, U, L, D, F2, B2> and then do a F/B quarter turn. Repeat with Orienting 4+ bad edges approach.
Orienting 4 + Bad Edges
Place four bad edges on F/B using <R, U, L, D, F2, B2> and then do a F/B quarter turn. Repeat until there are no more bad edges.
Orienting 6 Bad Edges
Often, 6 bad edges can be oriented more efficiently by placing 3 bad edges into F/B using <R, U, L, D, F2, B2>, performing an F/B quarter turn, and then using the 4 + approach to correctly orient the remaining 4 bad edges.
- Edge Permutation
- Corner Orientation
- VH Method
- Partial Edge Control
- EO Steps
- Lars Petrus' Petrus EO Tutorial
- Gilles Roux's Roux EO Tutorial
- Kian Mansour's Roux EO Tutorial (text based, more advanced)
- Kian Mansour's Roux EO Tutorial (youtube, mainly for beginners)