Here are some notes I have on voxel terrain assets for Unity.
There is a nice post here with some of the assets available. Although it may be slightly outdated it contains a good list for easy comparison of various assets. It also has a link to an older blog post with some other voxel resources and engines with a lot of people adding more links in the comments.
Voxeland – If you want something with great support and lots of features while still remaining fairly cheap in comparison to some of the others then you will want to check out Voxeland. It does get updates still and has excellent support. If you want biomes and a nice visual blueprint/graph layout to edit the features of your terrain then you can also get MapMagic which integrates with Voxeland. In fact it also integrates with plenty of other assets which is one of the major benefits to using these. They are by the same author. You also get full source code. I own Voxeland and MapMagic so I may be a bit biased to that combination but I’d love to give most of the others a shot too some time.
TerrainEngine looks really amazing! Unfortunately it’s also way too expensive for most people. Although if you have the money it seems quite powerful and might save you a lot of time so maybe it would be worth it. However it seems like there are some issues with communication and other unusual things going on with people getting scammed which may not necessarily be the fault of the author but still something to keep in mind I suppose. Apparently it’s coming to the asset store soon. I imagine it will be more expensive than all the others but we shall see. They are adding other engines like Citygine and Unigine and that seems pretty neat. If only the price was within our reach, we could have a chance to feel the awesomeness!
Voxel Farm is apparently complex with a steep learning curve but people can make some pretty awesome things with it. I don’t think it’s even limited to just terrain. I’ve seen games they use this in where they have buildings and spaceships and whatnot where parts can be deformed or broken. This is a little pricey and you have to pay more if you want the source code. The license may not work for everyone.
Ultimate Terrains I believe went through a long time of no updates or support but it seems to be getting some lately. It actually doesn’t look too bad. I want to try it out and see how it compares to Voxeland. Especially the performance which wasn’t superb in Voxeland from my little bit of testing so far but Ultimate Terrains looks like it might be ok. It appears to have some sort of built in block building system as well. It even looks to have a somewhat similar visual blueprint/graph builder like MapMagic has. My only concern is how well it would integrate with some other assets like Vegetation Studio or something like uConstruct or Easy Build System and how well it would work for networking. It looks like it might be pretty decent and it’ll hopefully improve further in the future if it continues getting regular updates. Also includes the source code.
MoleEngine – Unless the author of this asset can prove otherwise, it would appear as though their website is down and they don’t provide support on their unity forum post or answer any questions people have there anymore. They may still provide support by other means but I don’t own the asset so I’m not sure. It looks like they do release updates to the asset every now and then but they don’t seem like very big updates. They must be busy with other things. Either way it may do what it says it does. It may just not be very complex or feature rich in comparison to some of the others and therefore not really require too many updates. So if you want something like that then maybe this is the one for you but it doesn’t seem like something I’ll ever end up trying.
There may be others too out there somewhere. Don’t expect any of them to be too easy and do the work for you though. Especially if you plan to do any sort of networking you will likely have to write your own functions to send the updates to your clients or however you want to do it and hopefully you can work it out. Best of luck!