# Change the direction of sub-edges in quads

I try to change the direction of the invisible edge (fold line) of a quad (polygon).

How can I make the line visible, select and/or edit the direction of these?
(Without breaking the quad’s down into triangles)

Need an example?
A quad (thus 4 vertices making up 1 polygon),
Vertex 1 (Upper Left Corner)
Vertex 2 (Upper Right Corner)
Vertex 3 (Lower Right Corner)
Vertex 4 (Lower Left Corner

The fold line goes from V1 to V3,
and now we want to change this into: from V2 to V4.

Thanks for any info!

IMHO It’s not possible in blender. I’m missing that feature, too.

That would a shame, I hope someone still has a workaround, or any ideas?
(For instance how are these created / determined, based in what direction you draw?)

not certain but don’t think anything can be done afterward!

only thing is to do it in first place set you quad flat or coplanar and there won’t be any diag line!

the diag line is done during the render past i think
so if you make quad not equal to a plane or coplanar then you might get a diag line in render!

happy 2.6

It sounds like you are looking for the Rotate Edge command in the edge specials menu.

Go into Edge Mode
Select your line between V1 & V3
Ctrl+E
Select ‘Rotate Edge CW’.

… Actually I’m not even sure Edge Mode is neccesary

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@MikeJ: That will only work, if you convert the quad to two triangles. Than you can rotate the Edge. But if you convert it back to a quad, blender will recalculate the edge and turn it in the original direction.
In other 3D-Software the quad will keep the rotated edge.

CRUMPET: Are you trying to deliberately make a non-coplanar quad, and then change the direction of the resulting crease? I don’t understand what the situation is that would lead you to do this. The whole point of proper topology in quad modeling is to use the edge between two quads to define the form. If you are working low poly, then use triangles to define the edge, as that’s what your creating anyway.

Perhaps you could post an example.

the problem i think is that with non co planar quad you can see in render a diag edge in quad making 2 tri’s instead of a nice quad

and he would like to change the diag !

and i don’t remember that you can do that in blender cause this is done in the render past over which we have no control as i know of !

only way would be to change the location of the verts on the quad to change the direction of the diag but not certain how this can be done.

only solution i see is to make certain you don’t have non co planar quads only nice co planar quads
then you won’t see a diag in middle of quad!

but if it can be done please let us know !

happy 2.6

Hi thanks for all your replies,

It looks like it can’t be done as far as I can judge from your reactions so far.

It is not an visible (or selectable) edge (in edge mode).
Neither am I looking to add detail (coplanar).
Changing the location of the vertices won work either, as far as I can judge.
The vertices are all bound to other faces as well…
And as far as I know there is no information on what vertex is prioritized???

There really isn’t a need for an example image, since I understand most of you do understand perfectly what is requested, but there are only “workarounds”.
(based on the reactions so far)

So yeah, still hoping for a brilliant approach or solution

first delete the face that has the wrong fold, then create a edge where you want the fold to go, select all the edges in edge mode without selecting the desired fold edge, use F to make the face and it should align with the edge, remember do this without actually selecting the fold/edge, once the face is made delete the unselected edge and you should have the fold where the edge was

honestly this feels like a topic trying to poke out a flaw or something. autodesk charges people an absurd amount of money to make art in a desperately protected file format that refuses people to transition to anything other then there equally absurdly priced maya

Thread is 7 years old mate.

There is a way. But most don’t even know how. Because, there is no tool to directly deal with it.

Had the same prob wile working with very low poly models in LightWave 3D. The answer to this works in Blender also.

The best way in Blender to fix just one at a time, is first to delete the quad face. Select all four points in the direction needed so the normal of the new quad you make from them faces out. Counter clockwise. Start your selection of points where you don’t want a line to be. The line should connect your second and fourth points. Next hit F.

Now the line should be crossing where you need it to be. With no need to make it into triangles. You can keep it a quad, and have the center line where you wish. ^.^

See, it’s the order of the points the poly is made, that matters.

If you have a symmetrical model that you can mirror along the X, and one side of it is fine, delete the full side with the quads you don’t like. Mirror your model, and all the quads should be fixed.

It is what I do in Blender to fix what you are talking about. Hope it helps you, and anyone else that comes across this post. ^.^

Not so. I can be done. And I have just given the answer today.

Figured it out years ago for LightWave 3D. Just now finding out some don’t know how, and wish to know.

You are spot on as to why a person would want to do that.

Yes, it partly has to do with how the quad is rendered.

You are so close to the answer on how to fix it. If you was any closer to it, it have bit you on the ass. ^.^

You must delete the quad first, leaving the points it was made from. It’s the order you select your points before using them to make the new quad poly, is the answer. The line will be made connecting the selected points two and four.

In blender, select your points making sure point one is not where the line will start, then hit F to make the quad poly. That’s it. ^.^

select the 2 verts that you need the fold to be in press ‘J’ then select the 2 resulting triangles and press ‘F’

Select tha face you want with POLY.
Go to FACE / TRIANGULATE FACE
in the box above, select “the longer or the short way to cut”
Blender will change the direction of the edge, but Unfortunately the blender will create a real Edge. If you select the edge and delete, the invisible triangle will stay in the position

\o/ Thanks to JOW ( Jonathan williams ) that find it!

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Thanks, Taba! \o/