Greetings,
i’m being working with blender during some good time, but never face this:
this video get bugged sometimes while trying to skip.
here we can see automatic uv mapping while editing the mesh. After watch this, i start searching for this feature ( addon or blender branch ) but found nothing.
Any help with this will be great.
Regards, Scaredevil
Very interesting find, i use blender every day for all my modeling work and have never seen this either.
I first thought it might be a triplanar texturing setup on the material, but i’m not so sure now, if he is unwrapping it right away it might be some custom addon?
Technically the projection he gets looks like the automatic cube projection.
Which you can map to a script easily and execute right after an extrude (i actually have done this occasionally, to quickly block out levels with a checkerboard texture before i start modeling them).
However, having somewhat of the same result, it’s not what he is using, since his stuff updates even while he is still extruding.
What i mean is like this

The script for this is really just executing some selection/deselection and the projection command
import bpy
bpy.ops.mesh.select_all(action='TOGGLE')
bpy.ops.mesh.select_all(action='TOGGLE')
bpy.ops.uv.cube_project(cube_size=1, correct_aspect=True, clip_to_bounds=False, scale_to_bounds=False)
bpy.ops.mesh.select_all(action='TOGGLE')
I’m curious to see if someone else might know what this actually is.
Check out this link for better Explanation
This kind of thing only works for flat shapes. It’s basically just planar projection while editing. If that’s what you are looking for you might want to look up ProBuilder on the Asset Store. That’s pretty much exactly this - just inside Unity with coliders and Lightmapping UVs already set up as well. Also a ton of other useful extras. Plus it’s really easy to use.
It’s easily one of the best purchases I’ve made on the Asset Store so far. And I am not paid to say this.
There’s also a free version with limited functionality to test it.
http://www.sixbysevenstudio.com/wp-flexible/project/probuilder-for-unity-3d/
Thanks for the info guys, really appreciated. Sry for late answer, i was kinda away from the scene 
Blender have a tons of hidden suprises, too bad they’re not easy to find or simple use.