CraftStudio looks like a very promising indie game project which you can try out now in Alpha -- the latest game to enable real-time 3D content creation (including scriptable objects) and game building. Here's creator Elisée Maurer explaining how it works:

The game also has an Indiegogo crowdfunder, which has already raised its goal, but if you pledge $50, you get the source code to Project Waffle, the first game (a dungeon crawler) made in CraftStudio, so you hack it up and incorporate it into your own projects.

More features, drawn from the homepage: