You _can_ actually do this with just one quad per plane (or maybe 2 quads - one for the front face and one for the back face)... although you're right that you can't do it using CSS (yet).
A few years back, I wrote a tech-demo^W game for Ludum Dare (http://ludumdare.com/) based on using GLSL shaders to ray cast within a cube containing voxels. I then used these cubes as 3D "sprites" for the game.
A few years back, I wrote a tech-demo^W game for Ludum Dare (http://ludumdare.com/) based on using GLSL shaders to ray cast within a cube containing voxels. I then used these cubes as 3D "sprites" for the game.
See http://matt-williams.github.io/ld29/ for the game and http://ludumdare.com/compo/2014/04/28/voxel-map-algorithm/ for a write-up of the technology.