Necro explained some of it pretty well already.
A couple of questions to Cameni:
I read somewhere that one of the advantages of voxels over polygons lies in the creation of terrain and landscapes, is that true?
Are there other advantages/disadvantages?
The first assertion is a bit vague, so let me explain the differences first.
Polygonal terrain approaches the problem by composing a visible surface of the terrain, i.e. the physical representation that is being kept and rendered is of the terrain surface. Voxels basically encode the terrain volume itself.
Some of the differences are obvious: when I dig a hole in a voxel terrain, the volume gets physically (re)moved, unlike in the polygonal terrain, where I'm actually deforming a surface. Additional restriction comes from the fact that in polygonal engines the land surfaces are usually encoded as heightfields - a regular grid of heights, in order to save memory and enable some optimizations. This means that the hole would have to be vertical if it meant to use solely the heightfield functionality. Of course, you can use a different geometry generator for caves and tunnels, as we plan to.
You may wonder why we would bother with a polygonal engine when the voxels sound so superior. So, obviously, there's a catch
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- Representing world as voxels is extremely heavy on the memory and disk space, especially if you want to utilize the terrain deformation/destruction advantage[/*]
- You need to solve how to effectively render the volumetric data, reducing the huge amount of data flowing to graphics card[/*]
With voxel approach you are trading the ease of manipulation of terrain (world) data, for reduced efficiency and elevated storage requirements. If one means to generate an arbitrary terrain, then yes, voxels provide an advantage, but for a price.
Also, is a voxel based planetary engine possible and do voxel engines have "better" physics?
Additionally, can a voxel based physics system be integrated within a polygon based engine?
While in theory you could have a complete voxel planet, the short, practical answer is no, you can't
The thing is, voxels are still not very practical even for constrained game levels because of the requirements, and using it for whole planets would be many times more demanding. In theory you could do what Minecraft does, but since it should be a sphere, you won't have it aligned on all sides and thus even such coarse world with 1x1 meter voxels won't be usable for a planet. Going to finer representations is not feasible because of rapidly rising resource consumption.
Besides, it all expects that the world is dynamically generated by fractals. If you'd like a voxel world that uses real data, that would require even heavier processing, though I can foresee some techniques that could be used to combine it.
As for the physics, what you are probably referring to is again the dynamic terrain deformation. I'd say that with voxels doing this side of physical effects is much easier, it's basically the first thing any voxelist will show you because it's really easy while on polygonal terrain it's not trivial. But it doesn't balance out the disadvantages of voxels elsewhere, in my opinion.
Combining the two .. I don't have an idea how, at the moment. Maybe for some localized patches there could be a voxel space embedded, but that would effectively mean developing two engines anyway.
