FOSS gamedev and creative worlds

I was wondering how to make non-cubic blocks. I don't mean just triangles or cylinders, but custom shapes. If you don't know what I mean I will post an example, but I don't want to do that unless I HAVE to.

The only way to do that with nodes is by fooling the eyes into thinking it's an irregular shape using node boxes. See this topic for an example: http://forum.minetest.net/viewtopic.php?id=2153

I have seen those, What I meant was the ones built out of lots of small cubes (but not that small)

You CAN, however, build non-cubic "entities", which don't really take up space like blocks/nodes and can (optionally) move around dynamically in the game. I just build a new bag mod using them, with a 3D model for the in-world representation.