Having a trouble with Petrus

[Kaito Kid Cuber]

So I decided to learn Petrus method , but I am not sure if I learned it correctly .
The 2x2x3 is hard enough , lol .
But the problem is that I am NOT understanding The step after the 2x2x3 block . Do I need to make a cross on the 2 remaining faces ? And is there a specific Algorithm for that ?

 

[ruffleduck]

Rubik's Cube Solution - Petrus Method

 

[Thom S.]

Edge Orientation.
The Edges don't neccessarily need to make a cross but every specific Edge after EO needs to be able to find it's place with just R and U moves and be correctly flipped.
Example: on UL there is an Edge that belongs to FR. You hypothetically transport it there with U2 R'. It could now be right or flipped. If it's right, then it's correctly oriented, if not, then you need to change the EO.
Over time, you of course know how each edge looks like oriented and flipped.
If you do F' U F(one of the flipping algorithms and the first one you should learn.), then some edges change place, but FR and UL will have their orientation flipped. Doing the Inverse will solve this paricular EO case.
There are cases where 2, 4 or 6 Edges are flipped at once.
If EO is still too hard to grasp, i would advise you you to learn the Roux method for a short timeframe, as EO is also used there, but in my opinion in the easiest form..

 

[Kaito Kid Cuber]

Thank you very much everyone !


There is another question : Should the
OLL be with corners only after I do the F2L ? ( I just saw that in example solves )

 

[IsThatA4x4]

I am not a petrus expert by any means but:

// By the way, this is basically an expansion on what @Thom S. said, and it took me about 10 mins to write during which there is a new post so I am replying to your first question

EO (edge can be hard to understand at first, but gets better with some practice (e.g learning how to do ZZ). There are some rules to determine if an edge is oriented:
For edges with U/D stickers:
Edge in top/bottom
If the U/D sticker faces the top or bottom, the edge is oriented
Edge in middle layer
If the U/D sticker faces the front or back, the edge is oriented

For edges without U/D stickers:
For these edges, look at the F/B coloured sticker.
Edge in top/bottom
If the F/B sticker faces the top or bottom, the edge is oriented
Edge in middle layer
If the F/B sticker faces the front or back, the edge is oriented

An edge that is oriented can be solved with only the moveset <R, U, L, D, F2, B2, M2, E2, S2>. In the case of Petrus, after building the 2x2x3 block, orienting the remaining edges leaves the rest of F2L to be solved with only R and U moves.

How to orient edges
The easy way
-Put the block on the left
-If there are no oriented edges, do F' U* F (* means any type of this move e.g. U/U'/U2). This only happens rarely but it's good to
check
-Using R/U moves, put an oriented edge at DR
-Now follow these steps for any misoriented edge:
1) Use R* U* R*' to put it in the middle layer on the front
2) Use F' U* F to orient the edge, replacing another misoriented edge from the top layer.
3) Rinse and repeat

The harder but better but still intuitive way
-Certain triggers like F' U* F flip 2 edges at a time
-Other triggers like S R/R' S' or S U/U' S' flip 4 edges at a time
-You can use R/U moves to set up to either a 2 or 4 flip (in the case of a 6 flip, just learn an alg for it or make it into a 2 or 4 flip with a trigger), then do the 2/4 flip alg.

Hope this helps

// Wait actually, I guess I can answer your second question now:
Yes, OLL will only be with corners. This type of OLL is called an OCLL by the way.
There is a subset of 1LLL (1 look last layer) called ZBLL (we are considering a name change due to reasons stated in this thread )that is 1LLL with EO done. It has 493 algs, so only those at a very high level will learn them, but it is a thing.
COLL can also be used to do OCLL while solving the corners, giving an edges only PLL.

 

[PetrusQuber]

https://lar5.com/cube/fas3.html personally helped me when I was first starting out with Petrus. You're aiming to orient the edges, not to make an actual cross

 

[Kaito Kid Cuber]

I am not a petrus expert by any means but:

// By the way, this is basically an expansion on what @Thom S. said, and it took me about 10 mins to write during which there is a new post so I am replying to your first question

EO (edge can be hard to understand at first, but gets better with some practice (e.g learning how to do ZZ). There are some rules to determine if an edge is oriented:
For edges with U/D stickers:
Edge in top/bottom
If the U/D sticker faces the top or bottom, the edge is oriented
Edge in middle layer
If the U/D sticker faces the front or back, the edge is oriented

For edges without U/D stickers:
For these edges, look at the F/B coloured sticker.
Edge in top/bottom
If the F/B sticker faces the top or bottom, the edge is oriented
Edge in middle layer
If the F/B sticker faces the front or back, the edge is oriented

An edge that is oriented can be solved with only the moveset <R, U, L, D, F2, B2, M2, E2, S2>. In the case of Petrus, after building the 2x2x3 block, orienting the remaining edges leaves the rest of F2L to be solved with only R and U moves.

How to orient edges
The easy way
-Put the block on the left
-If there are no oriented edges, do F' U* F (* means any type of this move e.g. U/U'/U2). This only happens rarely but it's good to
check
-Using R/U moves, put an oriented edge at DR
-Now follow these steps for any misoriented edge:
1) Use R* U* R*' to put it in the middle layer on the front
2) Use F' U* F to orient the edge, replacing another misoriented edge from the top layer.
3) Rinse and repeat

The harder but better but still intuitive way
-Certain triggers like F' U* F flip 2 edges at a time
-Other triggers like S R/R' S' or S U/U' S' flip 4 edges at a time
-You can use R/U moves to set up to either a 2 or 4 flip (in the case of a 6 flip, just learn an alg for it or make it into a 2 or 4 flip with a trigger), then do the 2/4 flip alg.

Hope this helps

// Wait actually, I guess I can answer your second question now:
Yes, OLL will only be with corners. This type of OLL is called an OCLL by the way.
There is a subset of 1LLL (1 look last layer) called ZBLL (we are considering a name change due to reasons stated in this thread )that is 1LLL with EO done. It has 493 algs, so only those at a very high level will learn them, but it is a thing.
COLL can also be used to do OCLL while solving the corners, giving an edges only PLL.

I finally understood that thing . That you so much . I appreciate your help !