This is actually just a really efficient version of Minecraft's rendering engine...
Except it does not use blocks.
It does. It just has lots of them, rendered more smoothly.
Not that one, no. They claim it's pixel by pixel, no blocks. (As far as I can remember, I still haven't rewatched the video)
Well, the engine only cares about surface voxels when rendering, unless you want transparency of course, but the objects are indeed volumetric. Even when we're dealing with volumetric data, unless you're dealing with something like a physics simulation, medical data, or something similar, you don't need to specify every single atom inside an object. Atoms also don't need to have the same size as Notch implied.
You know, this gives me an idea, which knowing my lateness to the game has already been done and thought of. If the ray encounters an atom that is large enough to be encountered by a second (or in other words, the pixel is smaller than the atom given its relative distance to the viewer), couldn't you just subdivide the atom again to provide more detail? Essentially a 3D fractal. Lots of natural materials have (or can be approximated by) some easily mathematically defined patterns that could be used like this. More, you could discard these subdivisions periodically when they fall out of view. Not sure what the overhead would be for messing with this data structure that way. I get the feeling that's the major barrier for any of this stuff.
Each atom can be textured/altered in any way by a shader, much like what happens when a polygon get's 2D projected to your screen-space. So yes, an atom can contain a fractal shader. The shader pipeline in the graphics cards are pretty powerful and flexible, they don't care about what they are drawing from, only that they are drawing a single pixel on the screen. You can give the shader any data you want for it to work with. Normally you'd have a vertex shader that mainly computes 3 things, the relatives angles between light and surface, the normal of the surface, and the z-buffer (the virtual depth of your screen). They can also be used for distortion effects and the like. After that there's the texturing pass and then the final screenspace pass. I -think- you can fake a polygon to make use of the vertex shader, but with pure voxels you wouldn't be using it anyway. You could still make use of CUDA to calculate your voxel data and then use the pixel shaders for final effects, such as texturing, lightning, etc.
But it doesn't use raytracing!
As far as I know, no graphics card has drivers for raytracing yet, so no engine has been able to process it fast enough to make it usable in real-time without using custom-made hardware.
A lot of old games use raytracing, but that's beyond the point. Nowadays we have CUDA, thanks to nvidia. It allows you to make use of the GPU for pretty much anything. For example, I use this:
http://www.randomcontrol.com/arionEven on my single 275GTX, I can move around a ray-traced scene with several million rays being cast per second. It's pretty smooth. Of course, complex scenes where the light has to bounce around to reach a pixel, it will slow down, but decently made scenes let you move around while rendering in real time. Look at the little videos, that's basically the same thing a voxel rendering engine does, except that for speed you're doing a reverse casting to get a single pixel on the screen.
There are CUDA based voxel engines as well:
http://www.youtube.com/watch?v=Zl9CiGJiZucLike I said before, you only need one voxel model and then it can be instanced to near infinity with little to no problem.
More examples:
http://voxels.blogspot.com/http://www.youtube.com/watch?v=TjmRPjnWJ5ghttp://www.youtube.com/watch?v=oIQ0pqIeBcsThis is also a good read to learn about voxel terrains, crysis uses something a bit similar to this for distance terrain:
http://www.flipcode.com/archives/Realtime_Voxel_Landscape_Engines-Part_1_Introduction.shtmlThis is probably how crysis does it:
http://www.crs4.it/vic/cgi-bin/bib-page.cgi?id=%27Gobbetti:2005:FV%27Either that or it uses HLOD simplification.
Notch replies: http://notch.tumblr.com/post/8423008802/but-notch-its-not-a-scam
Notch has no idea what he's talking about, as usual.
Here's an old game demo that uses voxels-to-geometry in a way minecraft is far from dreaming of:
http://www.gpstraces.com/sven/HVox/hvox.news.html