The Sessile Question

Note: Along with plants, the scope of this discussion includes other sessile organisms, such as fungi, sponges, coral, etc.

Sessile organisms have always been murky in concepts for Thrive, with brainstorming pushed off into the distant future. With the microbe stage steadily approaching completion however, we are running short on time. So I think it’s important to start rounding out some thought, and I wanted to create this thread before I forgot my train of reasoning.

Before I or other developers devote brainpower to sessile gameplay however, I want to establish some basic information as to how ambitious we can afford to be. The original scope of Thrive proudly says that every sessile organism - plants, coral, sponges - will be simulated and playable, refusing to exclude sessile organisms from the player’s reach. I would like to revisit that thought and see if you guys think it is feasible.

Knowing that sessile biota play outsized roles in defining an ecosystem - trees defining forests, coral reefs supporting entire ecosystems, sponges lightening up the sea floor - how realistic is it for us to assume that every plant, reef, etc. will procedurally evolve along with the player? Knowing that these organisms will have to populate the planet at a far more dense rate than motile organisms, and knowing how important these organisms are such that their absence or presence might change gameplay dramatically, I have my doubts. But of course, I’d like to be proven wrong.

Would another option be better to utilize? For example, perhaps sessile organisms can be pre-generated and dynamic not through auto-evo but through a more simple mechanic using existing assets. Or perhaps a few plants and such are subject to auto-evo while the majority are not, and those non auto-evo organisms are forcefully implemented into the environment to populate the world.

I think we can make decently engaging player gameplay with sessile organisms, we just need to make sure we aren’t too ambitious with our scope so that we don’t fall into the early-Thrive trap. So input from our programmers and graphic artists would be appreciated before dedicating a major effort to sessile gameplay.

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I think making a new system of pre-made assets to create plants and things rather than what we already have just adds complexity, gives us more tasks to work on we don’t have people to dedicate towards, and wastes memory. Not to mention 3D artists have even more variable availability than programmers it seems (not their fault but, something we should probably keep in mind.)

In terms of the technicality of drawing many plants, it is actually easier than drawing even a few creatures. Static meshes can be batch drawn with very little issue, meaning you use the GPU to draw many things at once rather than draw meshes one at a time. Plants also completely ignore needing ai patterns because, they can’t act on them anyway. They’re basically props.

As for gameplay, I think it’s basically impossible to play as a plant unless you turn it into a sort of strategy thing (this could be as simple as introducing time-acceleration to where the actual game round is just showing you what your decisions in the editor actually did.) Because how do you play without playing? It’s not like you can do anything if you can’t move, the whole game is ‘swim around, get this, don’t die pls’


Sound good. I was just worried that asking the simulation to both perform auto-evo on a large amount of sessile organisms would be an unrealistic expectation akin to the absurd early scope of the project’s beginning. But I’m glad to hear it is feasible. Now I guess it’s a matter of ensuring that auto-evo creates a sufficient diversity of sessile organisms, like trees, shrubs, and reefs.

And I had the same thought you did regarding gameplay. I just can’t see any possibility of making sessile gameplay engaging that isn’t based on a time-accelerated strategy-esque game mode.

We can use the power that any good game or simulation does, we can cheat. For example we can set conditions for auto-evo to evolve at least a certain number of plant life and then just skip processing them mostly, if we can’t spare the computation time on them. Or we could maybe split auto-evo into two with the primary auto-evo only working on animals, and a much lower priority background task that the player doesn’t need to wait would be calculating plants. That way if the player is speedrunning they might not see much plant variety but in normal gameplay, I think we’d have plenty of background processing time.


In my mind the Sessile Question can be divided into mutiple subquestions which might be easier to answer seperately.

A. Should sessile organisms be autoevolved or static props?
I think making them static would go against very fundamental tenets of Thrives design philosophy and as others have mentioned, it wouldn’t even necessarily be less work intensive. Making autoevo simpler and more streamlined for sessiles like hhyyrylainen mentioned is a very viable possible compromise.

B. Should the player be able to play as a sessile species?
Mostly yes as barring the player from playing certain kinds of species would also contradict fundamental missions Thrive set out to do. I also imagine “sessile” to be a hard thing to properly define. We can’t stop the player from building a body plan which doesn’t lend itself to locomotion. Would we stop the player from leaving the editor if his organism can’t move?
An anemone moves one centimeter per hour. Is it considered sessile? Where do we draw the line?

C. Should we be expected to provide players who choose to play sessile species with engaging gameplay?
This question I believe can more readily be answered with “no” than the other two questions. A game can never be equally enjoyable in all of its parts and while it’s on the developer to give the game fun parts, it’s in the agency of the player to seek out the fun parts.
I guess the minimum we could do to make sessile gameplay less unplayable is giving players the option to speed up time when their movements are below a certain speed.
I’m unfamiliar with how difficult it is to implement such a time lapse system, but at least I know of a few games which have implemented it. Kerbal Space Program and Kenshi come to mind.
Nevertheless I’m sure that would be difficult to programm and even this minimum of making sessile gameplay less jarring isn’t a must imo but more of a nice to have.


It’s also worth considering how we intend to define when a species is to be considered sessile or not.

Since we already have a behavior slider that can make a species utterly inactive, we could perhaps use that to start with as a baseline determination.

Perhaps by setting the sessile/active slider all the way to the left, that would act as a toggle into a different form of gameplay. Changes such as disabling movement for the player, an increase in game-speed around them, autoevo not factoring in movement cost for fitness, etc would come into effect.

It would be pretty strange in the late game if cranking the activity slider could make a species with no legs or other form of locomotion zip around the place…

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An astute point.

I suppose it couldn’t ever be that simple beyond the microbe stage… but I still feel like it’s a great place to start. It’s that or just using motility as a determining factor…

In later stages, it should hopefully be very hard to become a motile organism when you’ve built yourself up over many generations as an autotrophic plant. You would presumably lack the organs necessary for locomotion, and the energy generation to fuel the movement.

I’ll be thinking on this.


I know that flagella are modified by some cells to allow them to stick to a substrate. Perhaps it could then be a variant of the flagella in the upgrade menu, greyed out until a player fully moves their activity slider towards being sessile. Then when the player presses the button to get out of the editor, a pop up saying something along the lines of “you are about to create a sessile organism do you want to proceed” shows up?

We can also add another function to this “sticky” flagella. Perhaps if you haven’t fully become sessile but have this sticky flagella, it will allow you to attach to an object and spring forward very quickly.

Of course, this presumes the implementation of procedural terrain.

To keep conistency between the stages, we might need to sharpen and differenciate our definitions: Are we talking about sessile species, or are we talking about non-locomotive species?
Sessile species are species which are fixed in one place and attatched to a surface.
Non-locomotive species are species which can’t move out of their own agency.
In my understanding all sessile species are non-locomotive, but not all non-locomotive species are sessile.
Let’s compare a venus fly trap with a man-of-war. Both only have one principle reflex which they can trigger: trapping prey when it comes too close.
The man-of-war moves with the currents of the ocean, but the gameplay of both species would be pretty much identical: You have to wait for long periods of time until prey comes and you snatch it at the right time.
So if playing the venus fly trap gives you the option to speed up time, you should have the same option when playing the man-of-war.

tl;dr: Maybe the more important distinction when switching between modes of gameplay should be “locomotive - non-locomotive” rather than “non-sessile - sessile”.

This is actually an incredibly good point. WIth this line of thinking a sessile organism is just a non-locomotive organism that as evolved some mutation to attach to substrates.

This is actually the case for most “sessile” organisms, barnacles start life drifting through the ocean until they find an attachment point, same with coral. And clams and so on.

And clams maintain the ability to move around into adulthood.

For a single celled version of this, look at the stentor, it has a mutation to attach to substrate , but it only stays attached as long as it is finding food. If it can’t it detaches and goes somewhere else. WHen hunting it is actually very actively moving around despite being sttached to a substrate.