This is a paid asset, but now you can download Ferr SuperCube Free.
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Ferr SuperCube v1.1 (Latest version)
Works with Unity 2017!
SuperCube is a Unity cube replacement that streamlines level design and prototyping, making everything fast, simple, and intuitive! Additional tools let you change UV types, apply materials to individual sides, optimize the scene by merging meshes, remove unwanted faces, and make good looking, blazing fast vertex lighting!
[ Site | Tutorial Videos | Demos ]
Features:
-In-scene scale/transform handles.
-Toggle visibility of individual faces.
-Drag/drop materials to individual faces.
-Use a variety of different UV modes.
-“Extrude” for fast duplication.
-Face slicing for vertex lighting/painting.
-Mesh merging tools for draw-calls!
-Proper lightmapping support.
-API for quick creation via code.