# Why dissolve edge acts differently

I want to understand how the dissolve edge works, so I tried the following ways, but they act different from one to another:

1.Remove single edge, end vertices remains still.

2.Remove connected edge, red vertices removed, instead adjacent vertices connected instead, how this would happen behind the scene?

They acts in different ways, from the first situation, I surpose remove edge doesn't impact any of the vertices the edge connected, but when it comes to situation 2, the whole idea proves to be wrong, I'd be appriciated if somebody could give me a comprehensive explaination of how the "Dissolve Edge" works behind the scene, thanks.

Edit:I suppose the second situation should be like this:

Edit: It is very informative, however, if the "Dissolve vertices" is selected as default, then why the end points belonged to the edges that is to be dissolved is still there, as the red dots showing below, the red dots is still there after edge dissolved:

If you are looking for some kind of thumb rule you can generally say: In default mode with the option Dissolve Vertices enabled, it works like this: if the edge you would like to dissolve leaves one or more vertices with each only connected to two different edges, than these vertices (and the connected edges) will be dissolved as well and the bounding vertices will be connected with a new edge.

Example 1:

Example 2:

• You are right, this is how it appears to be, what is the reason behind it still confused me Jan 19, 2021 at 8:48
• I've edited the text a little and will add a picture soon, since my explanation might seem incorrect, for a straight split edge doesn't seem to be dissolved, but it just looks like it, the image will explain it. Jan 19, 2021 at 8:58
• I've edited my question please check Jan 19, 2021 at 11:34
• One thing you ask in the edited question is why the vertices that build the dissolved edge are still there although Dissolve Vertices is enabled - that's simple, because they don't belong to the dissolved edge exclusively. If those vertices would be dissolved it would affect faces that didn't share the dissolved edge. Jan 19, 2021 at 12:45
• It seems that I've grasped sort of idea, but dig deep into it would make me confused further more, it is better to keep the rules in mind just for now which you explained so good, thanks Jan 19, 2021 at 14:03

The Dissolve Edges operator has options, which include 'Dissolve Vertices'. If 'Dissolve Vertices' is not checked, the the corner will not be cut.

As an aside, it's worth noting that using Dissolve Faces also gives the behaviour you were looking for:

(Top: Dissolve Edges, Bottom: Dissolve Faces)

• Yes; you're absolutely right. My explanation on which vertices are dissolved and which remain are only for the default mode with the option Dissolve Vertices enabled. I added this. I'll leave my answer because maybe it's still of some interest how Blender decides which vertices are dissolved. Jan 19, 2021 at 9:46
• @GordonBrinkmann Oh, for sure! I've been trying to work out the algorithm myself, as so often, we need to have a look at the code, if we can find it! Jan 19, 2021 at 9:55
• I've updated my question please check Jan 19, 2021 at 11:34

As simply as I can explain it is as follows;

In the first example, dissolving an edge, blender has two vertices remaining to support the geometry that is left behind from the edge.

In the second situation, if one dissolves a vertex that is surrounded in the way as pictured, them blender has no way to still support the remaining geometry, creating the resulting topology. Blender will dissolve further until reaching a boundary that will support the topology.

• In the second situation, after the yellow and white edge dissolved, the middle red vertex is supposed to be stay still, why the middle vertex can not support a rectangle? Jan 19, 2021 at 4:08