Overgrowth takes place in the savage world of Lugaru where rabbits, wolves and other animals are forced to use paws, claws and medieval weaponry to engage each other in battle. Combining 3rd person adventure platforming with intricate melee combat, Overgrowth achieves a unique feel. Overgrowth also benefits from Wolfire's brand new Phoenix Engine which has been built from the ground up to allow the use of cutting edge graphics, animation, and physics. Add to these exciting features Overgrowth’s realistic artificial intelligence and streamlined control system and the result is an astoundingly immersive experience.

Post news Report article RSS Feed OffTheGrid terrain: terrain mesh simplification revisited

We recently dramatically improved our terrain detail while optimizing the game at the same time. Here's how it works!

Posted by jeffr on Jun 3rd, 2009

What is OffTheGrid terrain?

OffTheGrid is a terrain technology we developed to bring detailed terrain data to in-game resolution without losing much detail. Below you can see a comparison between heightmap terrain (left), and OTG terrain (right). The OTG terrain is actually using fewer polygons.

Grid comparison

How does it work?

We start with a high-polygon terrain, and iteratively discard the least important polygon edge (as defined by Dr. Michael Garland's quadric-based polygonal surface simplification algorithm) until we get down to our in-game polygon count target. We then apply the normals and color map from our high-polygon terrain onto our simplified mesh. Here is a wireframe image showing how OTG terrain uses less polygons by choosing them more carefully.

Grid comparison

Why do we care?

With traditional heightmap terrain, it is only possible to accurately represent soft, rolling hills - small details like rivers, sand dunes, and cliff faces are all smoothed away by the grid. Using OffTheGrid terrain will allow us to portray a much wider variety of environments than we could with heightmap terrain. Here is an example of a small mountain detail that is destroyed by the grid (left). Please keep in mind this is just our base terrain mesh -- we are going to add vegetation, detail maps, and other environmental detail on top of this.

Grid comparison

Now that we have an effective technique to create an efficient base mesh, do you have any other ideas for how we can improve our terrain? I have a few ideas, but I'm not sure which is the most important.(permalink)

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Post comment Comments
NullSoldier Jun 3 2009 says:

Everytime you post an update it makes me want to buy your game just for the engine and modding tools.

+3 votes     reply to comment
DarkJee Jun 4 2009 replied:

well, why don't you buy it? :O you can mess with the engine in those alpha weekly updated when you preorder

+2 votes     reply to comment
jeffr Author
jeffr Jun 4 2009 says:

By the way -- the Overgrowth icon you see on the main moddb.com page was contributed by Tim Soret: Timsoret.com

+1 vote   reply to comment
Mischa_Silden Jun 4 2009 says:

..or maybe not but I still want your SDK :)

+1 vote     reply to comment
Armageddon104 Jun 4 2009 says:

Very nice :D

+1 vote     reply to comment
HANDofKANE Jun 4 2009 says:

I'd buy the game for the game,

... and then when I'm done living into the role of Turner, I'd mod it and make stuff, u guys are great!

+1 vote     reply to comment
awesomepossum Jun 4 2009 says:

Very clever!

+2 votes     reply to comment
SinKing Jun 4 2009 says:

I feel the same like NullSoldier, though that sounds a bit disrepectful towards the uniqueness of your game itself.
If we pre-order, when can we expect to try out the engine? I have no time for anything but my project(s) at the moment, but come fall I would love to get my hands dirty with that editor.

+2 votes     reply to comment
jeffr Author
jeffr Jun 4 2009 replied:

We've been giving people weekly alphas for the past 6 months. ;) If you preorder, you can try the engine as we develop it. Now is the best time to preorder, because this is when we need the most support -- we have no investors and are funded by your preorders.

+2 votes   reply to comment
Assaultman67 Jun 4 2009 replied:

I may just buy it now >_> ...

+1 vote     reply to comment
Pelf Jun 4 2009 replied:

Same here. I really want to get my hands on those modding tools.

+1 vote     reply to comment
Dragonlord Jun 4 2009 says:

Tried that technique 3 years ago too but ditched it due to a couple of nasty catches ( well, it's still available in the form of Terrain Meshes if people want to use it ) so test it well to see if it fits your needs. One of the problems had been memory consumption. This tech eats roughly 9-18 times more harddisk and GPU RAM ( depending if you use compressed vertices and aggressive chunking to avoid int indices ). And roughly 10 times more memory consumption on the GPU can be a show stopper especially for already large data ;) . But if you don't plan to go too high on the size of the terrain it should work. What's the target GPU ( RAM wise )?

+2 votes     reply to comment
jeffr Author
jeffr Jun 4 2009 replied:

David can answer more in detail on the implementation details, but the terrain is only a 2.2mb object file and it is actually more efficient than our previous terrain tech. We can store much more detail in the same number of tris and FPS actually increases using this new compression technique.

+1 vote   reply to comment
SinKing Jun 4 2009 says:

Ok, count on me! Hope our support helps you finish this project.

+1 vote     reply to comment
Jesternz08 Jun 4 2009 says:

interesting technique, makes me wanna go for some graphics programming right now.

+1 vote     reply to comment
PierreOfTheFrench Jun 4 2009 says:

Amazing as always.

+1 vote     reply to comment
chris_sloany Jun 4 2009 says:

awesome idea! looks fantastic!. will u b able to adjust how much detail you want, how much mesh, and can u adjust dynamic shadows. i.e sky brighting, SSAO, and toher stuff such as fog?

+1 vote     reply to comment
Assaultman67 Jun 4 2009 says:

Its really interesting that you used a normalmap on a terrain mesh ... i wonder how far that tech could be pushed ...

How detailed can the ground get ... could you say use one normal map to render features on the mountains (macro normal) and use another one to render the roughness of the ground right under you (micro normal)

For example, have a "micro normal" map only render a couple feet out (this would be a tiled normal transposed on the macro normal) , while discretely blending out at a distance to the "macro normal" only? ...

I guess you would have to implement a third map that indicates micro normal regions though (like what map goes where) :/ ...

+2 votes     reply to comment
CallmeMic Jun 4 2009 says:

Wow thats awesome O.O !

+1 vote     reply to comment
Dra6o0n Jun 4 2009 says:

I wonder if someone can make use of the engine to give players the ability to change terrains... Ingame!

Like excessive force to certain terrains will make them sink or if you use magic or "something" to raise the terrain...

+1 vote     reply to comment
Assaultman67 Jun 5 2009 replied:

That's been done before :/ ...

+1 vote     reply to comment
-Kwah- Jun 9 2009 replied:

Lots before.

+1 vote     reply to comment
-Kwah- Jun 9 2009 says:

But anyhow. I'm impressed.

+1 vote     reply to comment
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