How to render voxels? I have a voxel representation of a model of the human body in numpy and would like to render it directly in Blender.  Is there a file format for this?  Most of the ones I've seen use polygonal meshes (ie. .obj files).  In other words, could one render Minecraft directly in Blender?  (or if not, in Unity3D, Maya, UnrealEngine, or any other popular modeling 3-D software?)
While there are several file formats used for voxel data, they are used for volumetric data, such as smoke and fluid, which I doubt will help you.

As you have the data in numpy, I would suggest letting numpy save the data to file using numpy.save, but if you are using numpy to generate the data you can use numpy in blender and not use a file format at all.

By creating your selection of block types, you can then use a script to duplicate a block into each position.

import bpy
import numpy as np

objs = bpy.data.objects
scn = bpy.context.scene

scene_objs = [
        objs['sand'],
        objs['grass'],
        objs['water'],
        ]

voxel_data = np.array([
        [1, 1, 1, 1, 1, 1, 1],
        [1, 0, 0, 0, 0, 0, 1],
        [1, 0, 2, 0, 2, 0, 1],
        [1, 0, 2, 0, 2, 0, 1],
        [1, 1, 0, 1, 0, 1, 1],
        [1, 1, 1, 1, 1, 1, 1],
        [1, 1, 1, 1, 1, 1, 1],
        ])

for x in range(voxel_data.shape[0]):
    for y in range(voxel_data.shape[1]):
        obj = scene_objs[voxel_data[x,y]].copy()
        scn.objects.link(obj)
        obj.location = (x*2.1, y*2.1, 0)