itch.io

A collection or bundle of assets together as a single download or purchase

Things made with or for the open source 3D modeling software, Blender

Godot Engine - The free and open source 2D and 3D game engine

Pretty sure everything is indie on itch.io but just in case you want something extra indie.

Unreal Engine is a 3D game creation tool

Voxels are small geometric primitives used to construct larger worlds. Sometimes called 3D Pixels, they are typically cubes.