Doubles can cause all kinds of weird issues when modeling in Blender. In Blender versions 2.79 and earlier we could press W and select remove doubles. But how do we achieve something similar in later versions of Blender?
To Remove Doubles in Blender press M and choose merge by distance.
In the rest of this article, we'll go over doubles and how they end up in our model as well as the shortcut for it.
Before Blender 2.8 the shortcut was referred to as remove doubles, this was renamed to merge by distance as it more accurately described the operation.
It was also moved to the merge menu as this is where the rest of the vertex merging operations are. This made more sense than having it in it's own special separate menu with it's own unique shortcut.
We can change the shortcut to the original since Blender has all the functionality necessary to rebind it to the original shortcut if we'd like. Moving and renaming remove doubles mainly has just helped make Blender more intuitive and organized.
There are a number of reasons we might end up with double vertices. We may have accidently duplicated parts of the mesh and not moved them. We may have also moved two vertices to the same spot, possibly by sliding a vertex into another.
The basic idea though is that we end up with two verts taking up the same position.
A common mistake that results in doubles is when we accidently extrude a selection without moving it. This can happen if we accidently tap the extrude key and click before we've had a chance to notice.
Another mesh operation that might result in doubles in the loop cut tool. If we drag a loop too far up or down, it will overlap and result in doubles.
Modifiers may also produce models with doubles or certain mesh operations. This can be a result of either how we've configured the modifier or how the modifier works itself. One example of this would be the array modifier.
We might want to array a cube, so we just adjust the offset value. Usually, we would have the cubes placed edge to edge. While this will result in a mesh that looks correct the issue is that if we don't delete the faces that are interior to the array we will end up with a bunch of overlapping verts.
Sometimes when we import a model it will split the mesh up based on materials. This can result in doubles along the edge of materials. Some programs don't handle doubles very well or just export their models in a weird way.
If we're combining verts, we need to make sure they're actually merged and not just overlapping. Some modifiers can create doubles.
When we import a model for certain formats, we have the option to merge doubles before we import.
When using modifiers such as the array modifier we should follow a few rules. Modified meshes shouldn't create any interior faces or overlapping verts that don't merge. We should also make sure our distance values are set properly.
When modeling we usually won't have this issue but it's always good to try merging by distance occasionally just to see if we'd made any mistake. We can always undo this and merge them how we'd like once we've found them.
In the case that we know where the doubles are we can select both of them and then M and then at center.
We can also achieve a similar effect with the Weld modifiers. This modifier grabs groups of vertices by distance and then merges them.
To use the Weld Modifier to remove doubles:
The nice thing about modifiers is that they're non destructive and allow us to visualize the changes before we apply them to the model.
Sometimes the above methods aren't optimal because they create weird artifacts in the mesh normals since Blender doesn't know which way to make them face.
If we have a large chunk of our model that is duplicated and overlapping but not connected to the original mesh we can select all of it fairly easily and delete it.
To Delete a disconnected chunk of duplicate mesh:
We can also select linked with Ctrl + L and then press the delete key and select vertices. With this method we don't need to worry about altering the original mesh unlike if we had just merged by distance.
Doubles can cause us a lot of problems when working with a model, from messing with our normals to breaking modifiers. Blender provides a few quick ways to clean up doubles and knowing how to use them can save us a lot of time.
Just merging by distance is going to solve most issues with doubles but we also have a few other more specialized options for handling doubles and with these we should be able to handle most cases with doubles.
Thank you for your time.
