Fresh cube mesh was added, and shaped into a rectangular shape. Dark blobs appear to be showing when the mesh is selected in edit mode, zoomed in enough, and with the subdivision view to 2.
When object mode is selected the blobs disappear and the mesh appears normal.
Also, when zooming out enough, the dark blobs begin to disappear.
Is this a graphical glitch, or is this a problem with the mesh itself? The mesh is very new, just pulled faces and extruded 2-3 times. Thanks!
It's perfectly ok.
You are seeing it because mesh after using Subdivision Surface modifier cross boundaries of your low poly model and those have color with very low opacity but still visible.
Also they are dark because of your selected Blender theme which is if I'm not wrong 'Graph'.
If you don't like this appearance you can always switch to different theme.
No, there is no problem with the mesh, or with your computer, .What you see in edit mode is the effect of the subsurf modifier being displayed in edit mode, but without shwing the full result of the deformation.
If you want a full representation of what the subsurf modifier is doing in edit mode enable the triangle icon.
(form the Blender Manual):
Triangle
When enabled, the final modified geometry will be shown in Edit Mode and can be edited directly.
First, these dark blobs exists because of the sub-divided mesh is poking through its editing cage. It's perfectly safe.
Second, if you want to see your editing cage behind the blob, try this:
The button on the bottom right will make your editing cage visible even behind your object.
