This maybe the future version of my voxel based rendering engine Bengine, code name "RealBengine". Different from the current version of Bengine, which use ray-casting and is 2.5D, RealBengine will use ray-tracing and hence you will have 6 degree of freedom instead only 4. That means you can look up and down freely without any limit. The current version of Bengine can simulate look up and down a little bit using the distorted projection trick, but this is very limited - about +/-30 degree rotation around the X-Y plane at most. What's more, in RealBengine, you're working with real 3D, so most of the algorithm has been simplified because now you're using 3D vectors rather than fake 3D trick math.
And because of the essential difference in the rendering core, RealBengine will be a totally different engine and will be written from scratch in the future. However, RealBengine is not my priority for now. A similar example with source code using ray-tracing for voxel rendering can be found at:
An old working demo of RealBengine(Win32 binary):
This demo was written in HaXe/NME and compiled to the CPP target some time ago. This is just a simple quick proof of the ray-tracing voxel rendering algorithm. The demo needs optimization as it is slow (about 10~15 FPS in my test). A Flash/SWF version exists but too slow now.