A Comprehensive Concept for the Macroscopic Editor

Gameplay
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Felt this warranted a separate thread since it was a relatively significant undertaking, and rather grand in scope. I could have worked on this for longer, but I was losing steam and didn’t want this eating up more of my time for other priorities in Thrive, so I didn’t want to go down a rabbit hole. I’ll probably go back and add more things and visualizations clarifying certain areas.

I won’t make the text on this post too long, as the document is long enough. But the general idea of this document is that it presents a comprehensive design for the Macroscopic Editor. It is both a synthesis of the various ideas discussed in the prior Macroscopic Editor Thread (Macroscopic Editor, Progression, and Principles) and a fleshing out of the ideas there into an overarching cohesive document. And I think it is the most comprehensive, complete, and thought-through interpretation of the macroscopic editor we’ve ever had. Not saying it’s the perfect way to deal with things, but that it is a genuine attempt at covering this topic in a way that is relevant to the scope of the Macroscopic stages.

I don’t expect anyone to read through its entirely in one go. The hope is that if someone wonders how a specific system can be represented - perhaps limb editing and how such a system can handle arms, hands, wings, and fins in an engaging way, or the difference in anatomy between an exoskeleton and an endoskeleton, or a way to represent various integumentary structures - they’ll find a cohesive take in this document. And, if they think of any other adaptation or have one in mind reading this document, they can see a system that can integrate it.

An abbreviated version of this document: by representing various constraints , establishing relationships between constraints and specific stats, and altering how different parts and options interact with these constraints, we can present incredibly dynamic editor gameplay that creates a ton of replayability while strongly reflecting evolution. These constraints are set up in a way that hopefully allows for solid handling of various sorts of adaptations and body plans.

Well, that’s all I’ll be dressing the document with. The introduction section discusses underlying ideals and design principles leading me to craft the concept in this way; the rest of it is a description of respective concept areas. Read whatever parts of it you wish, and let me know your thoughts. I’m going to sleep.

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But you can’t stop me! (To be fair, I didn’t read it in one sitting)

I want to start by saying that I strongly agree with both the general principles in play here, and the basic layout of the systems. I really hope this can assuage some people’s concerns about a principally parts based system being too limiting or unrealistic. When the basic parts have extensive enough modification to them, it does not feel limiting (as you have in my opinion demonstrated). And realism compared to for example Spore does not come from “not having parts”, it comes from not being able to instantly overhaul your species, not upgrading by replacing parts with entirely different looking “superior” parts, and instead having a natural progression of adaptations to existing structures.

I think this has numerous benefits:

  • Allows auto-evo to work well (and this is absolutely critical)
  • Is consistent with both the design of the previous two stages and the player experience of the previous two stages.
  • We can take this essentially as far as we have time/resources for, continuing to add layers upon layers of modifications and more options for the various layers. Or cut it short to less options if necessary, to hopefully be expanded later. It is extremely scalable.
  • Since each layer of options is hidden by a previous layer, this limits how much a player is exposed to at once. Don’t need to worry about the slider for nails until you have nails, don’t need to worry about nail options until you have digits, don’t see digit options until you have limbs, etc.

So since I mostly agree, the rest of this comment will just be suggestions for refinement, and perhaps some nitpicking on specific examples for future reference.

General Comments

  • gradualism and adapting existing structures: I think I would like to see a bit more gradualism in the final design. Some things seem a bit too much like sudden big steps, instead of gradual derivations of existing structures. For example “placing mandibles” instead of “forming mandables out of gill arches”. Of course you so already have some of this like with the wings. But I think some things should be more explicit. For example, “foot with prehensile digits” should in my opinion be a required transition stage from “leg” to “arm”, not just an alternative solution.
  • stereotyping: I feel like some of the attributes you are ascribing to some parts and modifications are more things we associate with certain animals that have those traits, rather than attributes directly related to those parts/modifications. For example, the modification to “hoofed” suddenly making the streamline measure of the limb count more towards mobility.

Starting point

There is a conversation to be had on what the Macroscopic stage should start you of with. And that is strongly related to how far the multicellular stage takes us. The latter design is also not finished yet, I believe, which makes things more complicated. But I think my current impression is that expecting players to come out of multicellular with something like the Urbilaterian(a worm-like thing with at least a mouth and bilateral symmetry), might be a bridge too far. And I think that’s exactly what would be necessary for something that is easily converted into:

a length of metaballs connected to each other, akin to Spore… Should be symmetrical by default.

And note that with this level of complexity we would expect them to already have a mouth. I think our current trajectory on multicellular points more towards establishing the type of tissues you start macroscopic stage with, but not a strong body shape. Some things our sponge and jellyfish friends also seem like they would have diverged from the rest of us animals post-multicellullar stage’s 20-max cells. If this is the case, starting out with the type of organism you describe might be a bit odd. In which case:

A possible solution is to start you of without any inherent symmetry and just one metaball, that contains the tissues you made in multicellular. You can make it larger or smaller, perhaps add some patterns and repeating shapes to it, but you can’t place any more metaballs until you evolve a type of symmetry (which may have bilateral as the only option), at which point you are at the starting point you described here. Continuing to scale up your one metaball without placing more can end up with something like a sponge or placozoan.

(P.S. Thinking about this more, it might be possible to just make multicellular end with more complex structures than we expect at that number of cells, thereby letting the end-point of multicellular be for example the ubilaterian. Of course, this would mean that multicellular is the critical point where you decide on body types, symmetry, etc. I would still like a back-up option for evolving symmetry in macroscopic in case you didn’t do it before. Unless we want people to be accidentally be stuck as blobs.)

That selection of symmetry actually leads me to my next point:

Repetition and linked parts

In my mind, symmetry is just one variant of repetition: where in biology some things are seemingly copy-pasted (and maybe mirrored). The left and right arm are instances of the same thing, and genetically altering one typically also affects the other. Symmetry (in its various forms) is the obvious example, but you’ve also got repeating segments with legs in millipedes, leaves on plants, segments of plants, etc. There’s even partial repetition where some, but not all, attributes are shared between two parts. Your hands and feet are different in many ways, but hand and toenails did not evolve separately! Other examples are vertebrae, ribs, teeth, fins, etc.

So, I would like there to be a repetition or “linked parts” mechanic in the macroscopic editor, where parts are linked, and altering one automatically (and forcibly) alters other instances of the same part at no extra MP cost. In fact, breaking the linkage, in just one or multiple attributes, should cost MP. I can imagine a few variants of this:

  • Symmetry: wholesale repetition of the entire body.
  • Metamerism, or repitition of metaballs (and things attached to them). IRL this doesn’t really seem to be much of a thing for vertebrates (apart from the vertebrae themselves), but it definitely is in arthropods. So, rather than making it cheap for arthropods to add more metaballs and legs, this would mean arthropods (can) have a slider on their metaballs/segments for “how often do you want this segment to repeat?”. There’s your millipede.
  • Related Appendages: As in the limbs of us tetrapods. Some with mostly maintained linkage (elephants), others with very broken linkage (birds).
  • Branching: (This may be a big picture option in the same category as symmetry) As in plants. Essentially you (or auto-evo) just design for example a root, branch and leaf, and then set how frequently they should branch and repeat.

Bonus points: There is already precedent for this in Thrive! The multicellular prototype lets you place multiple cells of one cell type. Then editing the type means editing all the individual cells at no additional cost. Unless of course, you deliberately choose to split off a new type. (If I had my way, I would also eventually backport this to microbe stage for organelle modifications)

Comments on examples

Mass

  • I would like to see mass mainly be viewed as something of a side-effect of the changes you are making, rather than something you specifically increase in certain parts. For example, don’t increase the mass of a limb (thereby increasing some attributes), but instead increase the muscle volume of a limb (with appropriate results) and as a consequence, also increase mass. Because increasing bone density, adding armour and large claws also all add to the mass of the limb, but don’t feel like they should do the same as increasing the muscle volume.
  • The mass to speed effects seem a bit off to me. Particularly in the limbs: larger mass in limbs means more muscle power for locomotion (especially with my suggestion above). This would logically lead to higher speed, not lower. Having a trade-off between mobility and combat ability does not really make sense here (as anyone that has been kicked by a horse could attest).
  • Mass is not weight, and the centre of mass is not the same thing as the centre of weight/buoyancy. Weight is mostly your mass, but modified by the difference in density to the surrounding medium. This might seem like a trivial difference, but in my opinion it is not. Adding a giant swim bladder while you’re underwater (or the infamous hydrogen balloon above water) will increase your mass, but decrease your weight. Putting said bladder at the front of the organism moves the centre of mass forwards, but the centre of weight backwards.
    Mass and the centre of mass determine how the creature moves in response to horizontal pushing (by outside forces and the animal itself), while the weight and centre of weight determine how the animal interacts vertically with gravity. Obviously, if you use it as a measure of overall metabolism, that’s mass, not weight.
    If you don’t want to track both things separately, I would recommend only looking at centre of weight instead of mass (relevant underwater). Also for underwater animals, you do want to track overall weight and mass separately, unless you just ignore the difference and use a different system to reflect buoyancy.

Limbs

Is the free placement of metaballs on the torso, and then free placement of joints in 3D space still too free-form sculpting (especially for auto-evo). Though I guess in the end a position in 3D space is a set of 3 sliders. So that’s something for statistics and auto-evo to work on. Might even be nice as an alternate fine movement system for player use.

Vertebrate Wings

Definitely a big deal, and I am glad you were able to come up with a system that handles it so well. I especially love the option for which digits to include in the wing. However, for some reason I find myself disagreeing with a lot of the other small details here!

  • Is there any chance you got some of the steps backwards here? It doesn’t seem like fusing some joints will suddenly significantly arrest your fall. Joint changes is what I would expect in the transition to powered flight from an animal that already has flight membranes. Look for example at sugar gliders, with clear flight membranes but no powered flight.
  • On requiring a wristed appendage: I have to point out that by your definition bat wings are non-wristed (they walk on them).
  • On non-wing digits being weakened: I would much rather turn things around. Have the excess digits be mostly functional, but weaken the functioning of the wing as long as they exist. Thus providing potentially a gradual transition from fully functioning grasping hand to fully functioning wing, rather than the digits suddenly becoming worse for initially little benefit when you start transitioning to wing form.
  • I don’t think the flight membrane should simply transform into a feathered wing when you switch to feathers as skin cover. It’s a substantially different anatomy that has a lot of different implications, so it should be a complete alternate option that has feathers as a pre-requisite.
  • As an example of the gradualism I talked about at the start: instead of wing adaptation suddenly adding new effects to limb surface area, could we have the addition of a flight membrane unlock a slider for the surface area of specifically the flight membrane?

Mesoglea

As far as I am concerned, Mesoglea is not a skin attribute. IRL it is sandwiched in between the two main layers of cells that make up the body of cnidaria and ctenophores. So if anything, it is a form of skeleton/body cavity/transportation system. (their body structure is just very weird). Sponges have something very similar.

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First of all, really appreciate this reply. I’m glad to see you see the strength of the foundations of this concept: even though I really started believing in the strength of the concept as I could fit more and more adaptations within it, I was constantly wondering “is this something that won’t resonate at all with the community/other developers?” while making it.

You do bring up many good points.

I think one of the benefits of having something like center of mass relate to limbs is that the system has more of a framework to work with, even if placement is relatively free form. If the distance between a center of mass and an appendage/limb has an effect, then auto-evo has some sort of parameter it can work with. The additional joints and segments on an appendage is a bit more complex, but with that, something like the streamline relationship to appendages (longer appendages reducing streamline) can also have an effect. There obviously is more to think about with positioning, but we do have atleast some frameworks existing (hopefully) with a concept like this.

I think that’s a fair assessment for certain parts of this document. My approach to the concept initially was creating the fundamental constraints, providing a framework that can allow customization and choice in a way that is comprehensive but manageable, and demonstrating how tying these frameworks with these constraints can result in desirable gameplay. So in numerous parts of the concept, a general demonstration of ways we can fit in diverse adaptations took precedent over the exact nature of those adaptations, which leads to the point you bring up: correlation, or causation?

The following section of this post is as a whole somewhat rambly, but I think it’s all related to the points you bring up related to gradualism.

Relating to the above, progression is absolutely something that must be considered heavily in an extremely dedicated matter. Relating more to the approach of this document: this is an attempt to organize a large number of potential adaptations in as cohesive of a dynamic system as possible. In the hypothetical editor experience I visualized throughout most of creating this concept, I imagined a sort of “free build”, where the primary question was: how could we possibly organize all the information and detail needed to create an editor that could resemble as many life forms as possible? So again, in pursuing those general frameworks, there are areas which do need some considerable refinement.

I think there are three challenges to approach with progression…

  • How do we present progression in a way that encourages gradualism?
  • How do we adequately present this gradualism in a way that isn’t extremely convoluted, or overly simplistic?
  • How do we present gradualism in a way that doesn’t completely lock the player into a specific path, but also reflects the “commitment” behind several adaptations?

The first one I think is something that relates to the two other bullet points, and the second one is something that I think can be solved with intentional thought behind when “unlocks” occur.

The third doesn’t necessarily keep me up at night, but is one of the more challenging aspects of this editor. We don’t want there to be a case where the Thrivian version of an arthropod suddenly evolving an internal skeleton rather than an exoskeleton, or a mammal immediately transforming itself into a fish with gills occurs.

I think one approach we can keep in mind: we have to expect that some of this will occur in Thrive, just for the sake of player approachability and the fact that we are ultimately an editor-based game. Being a sandbox game, we generally avoid “locks” as much as we possibly can, unless that lock is tied to a stage progression. So there will be points of time where a player could hypothetically jump across an evolutionary “decision” rather easily, or revert a change.

So the way we approach this is - with this acceptance of the above fact - having a discussion and categorizing different “categories” of adaptations as ones that we are okay with being a bit more flexible for the sake of customization, ideal progression, and ease of development, and adaptations that we want to make sure are more strict and “commital”.

For example - in my mind, choosing between an exoskeleton and an endoskeleton should be really definitive, and I really would not want any ability to switch between the two after a certain relatively early point. Changing your Skin Type should be a really big deal. On the other hand, changes to your extremities are something that I can accept as being a bit more flexible considering how dynamic appendages and extremities can be.

I think ultimately, this sort of difference between commitment to an adaptation and not being committed to an adaptation will be making certain changes undoable if you have features which are derived from that adaptation. For example - if you have any sort of joint, you cannot switch between being something with an endoskeleton, an exoskeleton, or a hydrostatic skeleton. That way, you can switch pretty early on in the stage if you’re trying different things, but you wouldn’t be able to switch once you have any sort of limb or tail. Or for Skin Types, you cannot switch if you have certain adaptations or features that are unlocked by that Skin Type - for example, you cannot switch from reptilian scales if you have scutes, or from feathers if you have feathered appendages, etc.

That isn’t to say that these fundamental mechanics cannot be tweaked in order to encourage more gradualism, mind you. Just a general thought on the topic as a whole.

I do agree that the starting point of the Macroscopic Stage should be a bit before the urbilaterian, though I do think that level of complexity should be unlocked somewhat soon. Very interesting thoughts about symmetry, and I do like the sound of several of your suggestions. I think discussion of the beginning of the stage can be informed by an overarching framework such as this - and that discussion can alter that framework as a result.

Yeah, that was something I was beginning to think about towards the end of this process. As you mention, some of the most explosive animals have rather massive limbs because of their muscle. You see this in ungulates and species of feline, such as horses and cheetah.

I do still think that certain extremities should interact with the mass of an appendage - for example with damage or offensive weapons - and do think that certain extremities should use this constraint in a way that relates to mobility. But like you said, there definitely needs to be another layer of care dedicated towards musculature.

In my head, buoyancy ought to be a stat derived from your parameters and the effects of specific parts. So that can be an important distinction to declare; instead of mass or center of mass determining your behavior in fluids in broad brushstrokes, Buoyancy itself is an independent stat that mass and center of mass effect, but don’t necessarily define.

You do bring up a very interesting point with your distinguishing between CoM and center of weight (CoW). That is the tough part about designing an editor with such a scope; there’s a bunch of nuance for different situations. Because I do think it’s important that a generalized parameter like CoM exists, but it doesn’t necessarily act cohesively in all cases where we would like it to.

I wonder, if anything else, that specific parts like swim bladders can alter the effect that the mass of your torso/parts in a specific area has on your CoM, in a way that is more impactful in organisms with less mass but less impactful in an organism with more mass? That way, CoM remains as a definitive constraint and we still demonstrate the fact that larger mass organism do tend to have more weight, but we provide that sort of nuance needed behind animals shifting their weight with specific adaptations.

I will also bring up that I am open to changing the name of different constraints (especially for CoM, since that can be a very nuanced discussion).

Part of the reason why I wanted a parameter like CoM is that there would be some sort of relationship between where an appendage is on your body and the impact of that on various stats - being closer to your CoM favoring certain things, while being farther favoring others. Though if auto-evo still would find that difficult, there can be more rigid treatment of limbs in terms of maybe snapping onto a specific metaball for the AI.

That was me trying to find something that would work akin to the “wrist” or “joint” designation, which lets the system/auto-evo know “hey, the player/this AI is trying to evaluate this as a wing.” Cases like flying squirrels, sugar gliders, or the draco lizard honestly give me a lot of grief - could that potentially be a skin attribute? The answer there is pretty difficult to deal with; but hey, so is the topic of the origin of flight for paleontologists.

Fused joints could ideally be some sort of thing that signals the transformation of a limb the player was utilizing for unpowered flight/gliding into more powered forms of flight. It could maybe be dealt with like a special sort of digit/extremity that is applied at some point, though limiting when it can arrive would be an interesting question.

That is a good point, and something I thought about when creating that requirement as well - beyond bats, I’m sure many players would like to create some sort of wyvern-like organism, or a pterosaur-eqsue animal. I think that is enough to drop the requirement of having the appendage be wristed - the question yet again goes back to adequately limit progression to flight.

There also was a bit of question in my head of “how do we represent the biomechanics and physics of how wings are usually evolved near the front rather than the back limbs?” But I think that can be dealt with by having flight benefit much more from a forward CoM (really important for stability).

Perhaps the thing with flight isn’t fully a matter of making it be “locked” until really late, but instead have it be something that requires an extreme amount of commitment; you need to make sure your organism has lower mass, has a forward CoM, your appendages have to be really oriented towards a specific parameter, etc.

This didn’t properly address everything you bring up, but I do think there is something of value in the framework. Many of the points you bring up can be individual topics themselves - what really mattered to me with this document however is creating a sort of lens we could use to look at the editor with, and illustrating examples of this lens in action. It’s really hard to talk about the starting point of the stage without knowing how the editor works, how to talk about wings without knowing how appendages/limbs could work, how to understand how we can present dynamism without understanding how our stats could work, etc. So I hope we can establish atleast one basis of understanding that we can base some sort of future concepts on.

The above paragraph isn’t to say I’m not currently interested in discussing those individual topics you bring up, mind you!

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Right, and I hope I have at least demonstrated that there’s still a lot of room for design in this system. And that many disagreements on the smaller detail can all still be resolved within the same overall system, which is a good sign I think.

I was specifically thinking about how a joint, for example a “knee”, can theoretically be placed in many 3D locations relative to the “hip”: Forward/back, left/right and up/down. That’s a lot of variation that each need to have a statistical effect (and then have robust player and auto-evo editability), or a fixed selection (removing the choice), or have a “default” assumed by auto-evo with the player making purely aesthetic changes. But yes, I think this is possible to figure out.

To try to give some focused responses:

I think rather than answerable through unlocks, this is more directly answerable by how many intermediate required steps we design and require, in combination with MP limits. For example, coming back to your vertebrate wing example:
Let’s start with “limbless but vertebrate worm” for convenience:

  1. Add appendage.
  2. Add joint to appendage.
  3. Make appendage long enough (slider?)
  4. Add additional joint.
  5. Convert joint to ball-and-socket joint.
  6. Add extremity.
  7. Add flight membrane.
  8. Make flight membrane large enough. (slider?)
  9. Turn joint into a fused joint to allow for powered flight (?)

So, assuming you can only do one of these steps per editor session (and I think that should be the case), that’s 9 editor sessions to (entry-level) powered flight. That’s a fairly gradual transition I suppose. Of course, as it should be, each of those steps has its own advantages and disadvantages, and after each of them you could go in a different direction entirely. But in this case, for example “typical vertebrate limb” to “basic powered flight” is only 3 steps. If we think that’s too short, we can add more steps in between. For example, extending the membrane one segment/digit further is one step in itself, or maybe step 9 is just the start, and you still need to adjust more joints, enlarge different muscles, etc. That’s all just a question of execution of pacing in my opinion.

For one thing, I don’t think there is really any need to prevent reversing changes, at least as long as you don’t have later changes that are fully dependent on those earlier changes (apart from stage transitions for practical reasons). Realistically, some molluscs completely lost the shell, snakes lost limbs, etc. I think the more important thing is that both the gain and loss of any such feature (really, we should regard both as “change” in a neutral way) should happen in small enough steps.
Secondly, I do agree that having some things more locked in (rigidly or by incentive) would also be fine. Because ideally, you should not need things that require a different change 20 editor sessions ago. So you developed an exoskeleton, no vertebrate limbs for you. But say you feel the need to fly. Developers may or may not have allowed the “limb membrane” method to work for exoskeleton wings. But you do have the option for “insect wings”. And you might not have digited hands, but you have other ways to grab things. You have no spine, but you do have nerves and a brain to think with, etc. So any restrictions from previous choices just serve to make those choices more interesting, they should not make you feel “stuck”.
Thirdly, coming back to “any change is fine as long as there are enough steps to it” (and we are firmly into “optional stretch goals” territory here): I do think it’s fine to add some unconventional paths for changes that seem too large. For example: remember the discussion on squids in the community forums? That’s a shell turning into something like a partial endoskeleton, far later and in a far more complex and large animal than that divergence originally happened. So some bizarre path like a creature with a exoskeleton growing more tissues around it, eventually turning parts into an endoskeleton, does not seem entirely impossible. And I would be supportive of adding it, as long as actually performing it takes long enough. (Though again, this part isn’t necessary)

Slight detour here: you’re familiar with the concept of the “fitness landscape”? (Accessible explanation here) Basically, it’s the same issue as water always running downhill, and not being able to run up a hill even a little bit to get down even lower. You can expect both real life evolution and Thrive auto-evo to get stuck in local optima, not being able to get to other, more optimal, points because the steps to get there would require them to get less effective first. The player is always going to have more freedom, because they can take that leap, and I think that should work fine for giving the player enough freedom while we make auto-evo strict enough.

I agree, which is also why I feel like the option to develop symmetry (if it is not something started in Multicellular), should be immediately (or almost) available once you enter Macroscopic. Of course, that doesn’t mean you have to take that option immediately (placozoans sure never did), there are other options you could go for first.
I guess I should start writing my thoughts for the rest of the multicellular stage over on the other thread.

On the effect of appendages, I think it could work quite easily on a modifier/multiplication system.
For example, part of what goes into “speed” could be “muscle power of limb” x “traction” with type and modification of the extremities altering that traction. Similarly, damage from a claw crasping could be something like “sharpness” x “Muscle power driving the claw”.

So the advantage of having “weight” and mass (and their respective centres) tracked separately (with weight of course mainly deriving from the mass) is that we don’t have need a separate stat for buoyancy. Buoyant parts just have negative weight.

Yes, this is also a question of how complex we want to go. I thought having a (center of) “weight” and mass in the game would work, since you just use one at a time for different other mechanics. But one point is definitely easier to keep track of than two, and in a lot of situations,the two will actually be in the same place (for practical purposes).

I think if moving in this direction what I would do is:

  • Call it CoW instead of CoM. (Or not, after doing more research, center of mass/weight/gravity is used more interchangeably even in educational sources than I would expect/like. Center of buoyancy is usually kept more separate because it is used for more specific situations)
  • Have swim bladders simply move around the CoW in the opposite direction than what other types of body mass would do. That is instead of trying to modify what the mass around has as effect on the CoW. (Of course, this was assuming you control the size of the swim bladder independently. If this is just a trait you put on another body part, what you suggest sounds accurate)
  • I think I would flip that relation to organism size around! Or at least, make it neutral. Buoyancy (like weight/mass) scales with volume. Square/cube law says this grows faster than surface area when scaling up. This was vary clear with zeppelin design. So that’s at the same rate as the mass itself is growing, meaning large animals get just as much effect of offsetting mass with buoyancy as smaller animals do. That’s a big reason why marine animals can grow much larger than terrestrial ones.

Admitting here: I got things a bit wrong on my usage of CoW before: apparently the term is officially used for the difference between CoWeight/Gravity and CoMass in the situation where the gravity field is non-uniform. As in, the situation of a moon orbiting close to a planet. So that’s clearly not what we’re looking for. While the concept of “Center of weight modified by buoyancy” originally made sense to me, I have not found this concept used anywhere. Rather, discussion focusses on the centres of buoyancy and mass separately, because what actually happens is (taking the average across the body) the CoM is pulled down while the CoB is pulled up. Thus ending up with the CoM directly under the CoB in a fully submerged object unless that object is for example actively using fins to maintain a different orientation.

Starting from scratch again: Maybe the easiest way to handle this is to just go with basic physics rather than trying to avoid it? Each distinct part has a density, based on its base traits and modifications. “Scroll wheel” directly increases volume of selected part. Mass of a part is density x volume. Then, you take all that Mass to determine the Center of Mass. Assuming we’re a normal living thing on land where buoyancy is negligible, that’s done.

Going underwater, I think we have two options:

  • Go real. Take all the volume (ignoring density) to determine the Center of Buoyancy(or Center of Volume, I guess?). Then derive some things from the relative position of CoB and CoM, such as what the orientation of the body in the water is.
  • For the purposes of CoM calculation only, subtract the density of water from the density of all the parts first, making parts with less density than water essentially have negative mass. But would that even change anything for the end result? I guess I am out of my depth (haha) with this physics calculation.

In either case, for any effects where the actual “weight” the animal feels matters, for example for animals walking on the sea floor in the same way that animals walk above land, or for whether an animal floats or sinks in general, I think we do need to subtract the density of the water from the density of (parts of) the animal before calculating a “weight”.

Snapping appendages onto metaballs seems like a good option. I think there should be enough metaballs that it is not to restrictive, but it still provides a locked connection on at least one axis.

So for any of these that are ultimately limb-derived with a membrane (which includes the flying squirrel and sugar glider) I think should work the same as with bats. Though this does remind me that the membrane “Patagium”, should probably not only be selectable between segments of one limb back to the main body, but also extendable to metaballs further back and even to other limbs. Because that’s the case with bats and pterosaurs as well, it’s just more apparent with these squirrels. As for how to determine when to evaluate it as a wing:

  • I think there should be an explicit option to add a small starting flight membrane (patagium) to a segment of the limb. This should trigger the “flight calculation”.
  • As you expand the membrane, this would first just be “parachuting”, slowing your fall.
  • Expanding it more gradually decreases fall speed, and increases forward speed at the same time. (gliding)
  • If it’s big enough, you can make a joint change (?) at the shoulder that adds initially weak powered flight.
  • You can then increase “flapping ability” by increasing the relevant muscle/muscle containing part.

Would that work?

As for the Draco lizard, I actually forgot these existed, and certainly never realised they were not using the limbs. Looks like they’re actually suspended on ribs? It’s rare enough that I would not put it at a high priority. Only other example I can find is… gliding snakes (what on earth…). But there are other lizards with less extreme types of body flattening for gliding, or skin flaps.

For skin flaps, I guess that’s just a flight membrane attached to a metaball without being attached to limbs. With probably lessened gliding ability but also no effect on normal limb function.

For the flattening body type: Ribs are probably something we want to represent, right? Also, I think you’ve discussed changing the shape of metaballs in the editor before. If so, this is a function for making the flattening of a metaball dynamic, which you can add if you have ribs. Would affect your temperature regulation, and have a small gliding ability attached that gets significant if you go very extreme with the flattening or in combination with membranes and other characteristics.

Then finally for the Draco… I guess it’s a metaball option for growing out your ribs into the skin membrane, letting you expand it more while remaining foldable and not taking up use of the limb? It would obviously come with the loss of many of the benefits ribs would normally give. And I guess this may not have an option to produce powered flight.

I think position of the wings relative to the CoM should be a big thing here. Though technically we’re talking about the centre of lift here. Yay, more centres! A cursory search suggests for an aircraft the most important thing is for the center of lift (wings) to be just slightly behind the center of mass for stability (otherwise the plane has the tendency to flip). Though at least birds might be less stable, using active movements to balance things out, perhaps similar to fighter planes.

But overall having the wings close to the center of mass seems like it should be encouraged.

Like I more or less started with: I do agree that we shouldn’t think about this in terms of “late unlocks”, but rather something that needs many focused steps to get to.