There’s not too much to say about the obvious mechanisms of the 0.5.0 in-game grass: it uses the billboard system which I explained a while back. I could mention the other technical details: it only draws a few, nearby, vegetation nodes, grazing affects the length of the entire node, it fades out at a distance because there’s way too much of it to draw it across the entire map… okay, done that, now what?

Well, seeing as how talking about implementation is boring, I guess we might as well talk about the design aspects.

The moment I decided on grazing as a feature for 0.5.0, I knew I’d have to represent it somehow. The grass itself, though, wasn’t originally meant to be that representation. Indeed, I’m still not entirely convinced that grass is the best representation for it: rendering grass has limitations that make it less than ideal.




Okay, I’m in the middle of typing up this post and I’m beginning to realise that the height of the billboard grass really isn’t the best way to represent grazable material. That’s what I get for blogging about a feature I’m in the middle of coding. Oh the joys of an evolving project.

Okay, new approach: I’m going to use this post as an opportunity to get my thoughts in order before I go off and play with the code a bit more.

The plan (prior to about about 30 seconds ago) was to include a grazables container or bucket within each square of terrain. This container would contain all the energy that creatures could graze from, and how ‘full’ it was would determine how long the grass in that square was. Fertility loss due to grazing would occur when the bucket was empty and had to ‘buy’ more energy to regrow.

Documenting my design decisions. I am a professional and I act like a professional.

The big pro to this approach is that grass height shows you at a glance how much grazable energy the local area has. Unfortunately, there’s also a lot of cons:

– all grazable scatter-material grows like grass and is edible, regardless of what it actually looks like. This includes pebbles on rocky terrain, shells on the beach, salt in a salt plain, and lava rocks in lava.
– grass in an area is all the same height. Since an ‘area’ is an exact square of roughly 10m x 10m, this would be especially noticable at borders where grass on one side is short and grass on the other is long.
– fertility loss is applied on an area-scale, not on a local one. A creature eating at the very corner of an area will affect the fertility of ground 14.1421m away (+/- 10m, anyway. Oh who am I kidding, I have no idea how big the vegetation squares are), while not affecting the ground just behind it.
– Grass is invisible at a distance, so you can’t see the direct effects of grazing from far away.

Yes, the rocks are edible. Why wouldn’t the rocks be edible? Stop being so carbon-based in your thinking.

Now, all of these are things that can be dealt with to eliminate or reduce their effect: scattering a squares vegetation a bit beyond it’s border would blur the straight line between squares, by applying fertility loss on a macro level makes it less apparent that it’s related to overall area and not to the actions of individual creatures.

But what if we could deal with all of these problems just by changing the way ‘grazable energy’ is stored? This is the idea I’ve just had:

Eliminate the energy buckets in terrain squares, and effectively remove all terrain-based control over grazable energy. Grass no longer has any limit: creatures can just keep grazing and grazing within their biome… until the biome changes.


With this system, a creature emits a ‘death aura’ while grazing, gradually reducing the fertility in a small area directly underneath themselves. Eventually, the biome under them degrades. This introduces a direct correlation between fertility and energy: a creature absorbs fertility from the ground and gains energy in exchange.

Do vegetarians usually suck dry the very soul of the planet? Oh no wait that’s vegans. Ba-dum tchch! (teasing vegans. I’m so original)

Since grazables are no longer dependant on area but on biome, we’ll be able to introduce a variety of biome dependant statistics (starting with a simple isGrazable boolean) as a central function of the simulation, rather than as something tacked on afterwards as was originally planned.

A conventient bonus is the fact that the ‘death aura’ code already exists, in the form of biome stabilisation from trees. The only difference is that where tree’s stabilise the habitat they’re best suited for (with the exception of some unbalanced pioneering species which make the simulation more dynamic by stabilising towards biomes they can’t survive in), grazing creatures stabilise the habitat towards arid, desert biomes, and then have to move on to find more grass.

Of course, I’ll have to rework some of the code for this: the ‘buckets’ system already exists in the development version. But that’s the nature of prototyping.

[The following day]

Welp, that’s done. This actually makes the environment feel a lot more ‘directed’, since you can now pinpoint the source of every fertility change: it’s either grazing creatures, trees or water. I might have to add a few more fertility-change sources, just to make it less predictable.

Ultimately, this change leaves the grass itself as little more than an aesthetic item. Oh well: the system’s in place now, it’s useful in defining the presence and quantity of grazable material in each biome, and when even the placeholder art looks good, you know you’re doing something right..



He doesn’t mean it about the vegans. We actually think vegans are pretty awesome: it must take a lot of willpower and strength of conviction.

Please don’t kill us with your psychic vegan powers.


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  1. #1 by Wrath on January 13, 2013 - 8:37 am

    I really like the concept but what about including active predation of grazing animals? Almost all of the carnivorous species i have encountered have just been scavengers for the most part. What about coordinated prey vs. predator relationships that effect behavior? That may be a bit of a stretch but it would be really great in future developments.

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