Since there seems to be some interest in voxels lately, I thought I'd post an older project I worked on. This was a submission for a TigSource competition, we were given some random assets (art, sound effects, sprite sheets, ect...) and a month to come up with whatever we wanted. I went with a 2d sidescroller with a 3d twist. Given the 1 month limitation I only had 1 level, no enemies to shoot/kill, and no sound, but overall I found it to be a fun experiment.
The voxel 'engine' is implemented in a single shader program. Each voxel tile is 16x16x16 voxels, and the map consists of 256w x 128h x 64d tiles. The 'engine' was just a simple grid based ray casting algorithm. Performance was surprisingly good getting a consistent 30fps on a nvidia 9800 gtx, and 60fps (capped due to vsync so probably higher) on a ati 5770 (also implemented it in sse assembly and got around 4 fps on a single core just to see). Rendering resolution was 960 x 720.
I've provided a small video of it being played below.