What would be a better bone segment to make the base of my 3D model; the bottom of the lumbar, or the bottom of the sacrum? Would this vary between a human and a catgirl?
Also, how agile are tails? Would I need a certain number of caudal vertebrae to be independently controlled?
One more thing: What would be more appropriate to attach the legs to, the top or the bottom of the sacrum?
>3D model
Are you making a figurine to print? A model for a game mod? A model to animate? Depending on your answer, your base will vary.
>Would this vary between a human and a catgirl?
The sacrum? Yes, it is where the tail attaches. Your base will stay the same.
>Also, how agile are tails? Would I need a certain number of caudal vertebrae to be independently controlled?
They are just as flexible as, say, a snake. Rig it with about a dozen bones. Real cats have more, but that will give you all the flexibility you need. Could use fewer joints by just keeping the middle of the tail straight.
>What would be more appropriate to attach the legs to, the top or the bottom of the sacrum?
Legs don't attach to the sacrum, silly, they go into the pelvis. Your hip bones do attach near the top though.
>>2024029
A model to animate, and I'm trying an experiment in model topology where I see if I can get one model to be able to be roughly reshaped into numerous mammals which could save a lot of work.
And by leg attachment, I meant to ask which vertebrae the pelvis follows.
So, the pelvis follows the top of the sacrum? That's incredibly inconvenient, unless I decide to have it so that the base of the model with regards to posing is not the hips. I really don't know where I should have it.
>>2024076
I like importing the bones and muscles from MakeHuman into blender. They are anatomically correct already and then you can mush them into whatever you need from there with a bit of patience.
I think I need to explain my problem better.
Here's what a skeleton in Blender looks like.
I can only connect bones to the skinny end of a bone (This includes the legs which I have indirectly connected), and the point on the skeleton where two fat ends touch is pretty much the pivot point for the entire model, the point that won't be moved by any bone rotation.
Spine bones from bottom to top are caudal, sacral, and lumbar respectively.
Currently I have the legs attached to the top of the lumbar, but that's not accurate, so I'm going to have to flip one of the bones.
For this skeleton to work well with everything from humans to long-tailed quadrapeds, which option should I pick?:
>invert the lumbar, making the pivot point for the skeleton the joint between the lumbar and thoracic while the legs (and thus effectively the hips) attach to the joint between the lumbar and sacrum
>invert the sacrum, making the pivot point for the skeleton the joint between the lumbar and sacrum while the legs and hips once again attach to the joint between the lumbar and sacrum
>>2024162
By the way, I could make anywhere in the spine the pivot point of the skeleton, but either the bottom of the thoracic or sacrum seem to make the most sense.
I guess which of the two to pick depends mainly on two things:
>does the sacrum get involved in tail movements?
>which moves around the least?
>>2024162
>invert the sacrum, making the pivot point for the skeleton the joint between the lumbar and sacrum while the legs and hips once again attach to the joint between the lumbar and sacrum
Seems to make the most sense to me
>does the sacrum get involved in tail movements?
No
>which moves around the least?
Sacral
>>2024187
Really? Surprises me, I would have thought the middle of the torso would make the most sense, just felt I should ask anyway.
>>2024195
I say that because you want it to work with quadrupeds too, which do way more bending in the middle than people do. The ass of most things is pretty fused and is the anchor point for everything else.
>>2024203
Bear in mind that it's the base of the sacrum that'll be the pivot point. Even with something like a cat, is that really right?
>>2024195
part of the problem is there's actually multiple pivot points
if you swing your hips dorso-ventrally 20 degrees, the pivot is actually taking place in five or more vertebral joints.
how to model that is pretty arbitrary. Pick any point from the anterior or the sacral series up to the middle of the lumbars and call it your pivot for axial rotation.
>>2024212
So, you're saying the joint between sacral and lumbar would probably be best?
Unless I join the hips to the bottom of the sacral (Not sure if that's right or not), then I can't do that.
Do the hips join roughly to the bottom of the sacral?
>>2024216
in humans (like most animals) the sacral series is fused into a single bone by adulthood.
the hips join essentially along the entire length of the sacrum.
so if we're talking about how the torso moves compared to the hips, the pivot would be above the hips (proximal, anterior to the sacrals, closer to the head than the tail, cranial to the sacrum).
If we're talking where the legs pivot from the sacrum that's going to be a bit lower. Closer to the middle or bottom of the sacral series depending on the animal. (distally, caudal to the lumbars, caudally)
>>2024222
I'm just talking about what makes sense for a pivot for a whole skeleton.
>>2024223
yeah, it's all relative.
if you're talking the part that moves least in relation to the environment, that's going to be around the belly button. The center of gravity.
in quadrupeds the COG varies by gait.
>>2024225
I don't really like either one because the leg joint is too high (or proximal).
and I'm not really sure it matters regarding axial rotation or pelvic declination since both of those actually happen over the entire lumbar series.
I don't use the program you're working in, but if I was going to model it I'd want the leg pivot anywhere from 1/2 way down the sacrum all the way to the bottom. In humans it's actually below the bottom of the sacrum.
the torsion of the torso is probably centered about half way up the lumbar series, though I guess the lumbar/sacral isn't terribly far off.
>>2024225
notice the leg joint is below (distal to) the sacrum.
>>2024228
But the hip is attached to the top of the sacrum it seems.
>>2024234
depends which rotation we're talking about.
axial rotation of the hips is above the top of the sacrum.
fore-aft rotation of the leg is below the bottom.
the pelves themselves are firmly fixed to the sacrum, and move with it as a unit.
>>2024241
Dunno what that jargon for rotation means.
>>2024254
I know.
that's why you're not going to get a real answer.
the skeleton doesn't have just one pivot point, it's got hundreds. The legs, hips and torso don't meet in one single spot. The hips and torso meet in one place and the hips and legs meet somewhere entirely different.
>>2024258
But if the belly moves least, that'll be my "pivot point" I suppose.
>>2024264
in a walking human that's probably the spot.
the base of the skull doesn't move much either...
you've got the same problem with quadrupeds like cats, they've actually got two pivot points when they're walking. The top of the hips and between the shoulders.
>>2024267
I just remembered a big problem with using the belly as the "pivot point" though; wherever the pivot point is, I'll have a sharp bend rather than a smooth curve when I bend it.
>>2024270
the only real spot on a person torso that has a sharp bend like that is the ass.
I dunno man. If you want the spot that bends most but is closest to the belly that's probably the bottom of the sacrum.
>>2024271
So, I should have it like this?
>>2024274
that's probably how I'd do it.
it's not actually accurate as far as twisting of the hips goes, but it's a decent average. And it puts your sharp bend in the right spot.
>>2024277
Why wouldn't it be accurate for hip twisting?
>>2024279
the pivot for hip twisting is at the top of the sacrum, not the bottom.
but for forward bending the main pivot is at the bottom like you have there.
it looks like you've also got a joint at the top of the sacrum which should simulate lordosis and kyphosis.
>>2024281
The way it works is that I can use each ball as a manual joint, and each bone I can have split into segments which will curve automatically.
I'd be able to rotate the sacrum in relation to the lumbar, the only issue with the fat-end to fat-end thing is that if I split a bone into segments then they won't curve into each other at that joint.
>>2024283
I think that's how you want to do it then.
the sacrum functions as a single block with the hips, so there shouldn't be any flex in the sacrum or in the distance between the heads of the femurs.
modeling it that way shows the bend of the ass, which is going to be important for bending over or sitting.
>>2024285
I build the model around the skeleton, so would it be necessary to use that bone structure to show the ass bend?
And I am supposed to tie the hips to the top of the sacrum rather than the bottom, right?
>>2024283
>if I split a bone into segments then they won't curve into each other at that joint.
If I'm understanding you then this is how you need it to be.
since neither the sacrum or the femur is jointed anywhere in the middle.
>>2024287
Still wish I wasn't moving the skeleton ass-first, but oh well!
>>2024286
>would it be necessary to use that bone structure to show the ass bend?
no, I don't think so.
I'm used to biomechanics, so I think in terms of actual bones, but there's no particular reason you'd have to model the actual skeleton.
>I am supposed to tie the hips to the top of the sacrum rather than the bottom, right?
"hips" is ambiguous.
in the human skeleton you can treat the hip bones as THE SAME as the sacrum.
if you mean the HIP JOINTS, (the femoral ball/socket joints) those are at the bottom of the sacrum.
>>2024288
I probably don't understand what the program is doing. Like I said I'm not familiar with it.
in locomotion though the skeleton is essentially moved from the ass or the neck, depending on how you look at it.
>>2024290
>bottom of the sacrum
So I need that part as a thin end so I can connect the legs to it.
But that doesn't play nicely with the current call to have the bottom of the sacrum as a joint between two fat ends.
>>2024293
my understanding is that a fat end to fat end connection gives you movement greater than 90 degrees at that joint. If that's wrong then you need the fat end to fat end joint at the top of the sacrum or somewhere in the middle.
>>2024301
Here's the properties of a fat-fat joint:
>bends will always be sharp, smooth isn't an option
>I can't connect bones to that join, a thin end is required
>the two bones that meet for the joint are not affected by the movements of any other bones
All joints have unlimited turning, by the way.
>>2024304
ok.
well in humans and most mammals there's no actual joint in the sacrum or pelvis (hips).
there's a joint at the top of the sacrum to the spine, and there's two joints at the bottom for the legs.
honestly I don't know how you'd model that, but the most severe bend in the torso is at the legs. The ass has the sharpest bend not associated with the center of a limb.
that ass bend is just where the limbs meet the torso though. At the bottom of the sacrum. it is the sharpest bend on the spinal column.
>>2024304
>I can't connect bones to that join, a thin end is required
also this seems to be the problem. I'd guess we have to abandon that joint if we can't attach two legs to it. Maybe just stick the joint in the middle of the sacrum? Like pretend the sacrum has a joint in the middle and call that your sharp bend? It doesn't sound like your program can actually model human hips accurately.
the other option is to put your fat end joint at the bottom of the sacrum and have your legs attached higher, but that's not a very accurate model of the base of the tail in cats. It might be right in a bipedal cat girl though.
>>2024307
I guess I just need to weigh the benefits of my options then. Would it be too inaccurate to have the legs join to the top of the sacrum instead?
>>2024310
Unless I divide the sacrum manually, I can only attach a joint to the top or bottom (and not the bottom if it's the fat-fat joint)
You seem to be telling me to do that, but if I split the sacrum in two I can't both make it the fat-fat joint and the leg attachment point.
>>2024313
>Would it be too inaccurate to have the legs join to the top of the sacrum instead?
no, I think that's going to be your best compromise.
it's not accurate but it's probably as close as we're going to get since you need a narrow end to attach legs.
>>2024315
Even if it's okay, I'm not sure about best compromise.
Having the fat-fat joint between the lumbar and sacrum instead doesn't sound that bad, and it'd let me attach the legs at the bottom of the sacrum.
Or is attaching the legs at the bottom of the sacrum just as inaccurate as attaching it to the top?
>>2024316
>is attaching the legs at the bottom of the sacrum just as inaccurate as attaching it to the top?
no, the bottom is completely accurate.
in real human skeletons the legs attach at almost exactly the bottom of the sacrum and the top of the tail.
in cats the legs attach near the middle of the sacrum.
>>2024318
Alright, then maybe I will have it like that. I can always change it later if the sharp bend at the hips seems too severe.
>>2024316
>Having the fat-fat joint between the lumbar and sacrum instead doesn't sound that bad
I'd say that's best for the human, but not really best for a cat girl tail.
but it would make the cat girl's ass stick out in a nice mammalian lordosis, which is universally sexy to humans and cats....
>>2024320
>>2024316
notice how the cat bends her ass upward to mate. Humans do this too.
this is a bend at the top of the sacrum, typical mammalian lordosis behavior. Is sexy.
>>2024322
I've spent a lot of time since my first anatomy class studying the mammalian lordosis.
Mostly at Disneyland. It's funny how hot a swaybacked woman looks, or how hard my own back arches when I slam my cock into her and come.
exaggerated sexual features are common in art though. And lordosis is certainly a sexual feature.
>>2024323
How noticable would you say a failure of the lower part of the lumbar to neatly curve would be then?
The cost of that setup is that.
>>2024327
I think it's an appropriate failure if you're trying to make sexy gurls.
the angle of the lumbar series to the sacrum is more pronounced in fertile women, and society in general prefers a more steep angle for the ass. It's pretty much universal whether we're talking Latinas with their fat ass sticking out or hotentots with their exaggerated lordosis.
I don't know though. Try it and see what it looks like?
>>2024329
Very well, brb in a bajillion years because the mesh topology for this is gonna be crazy hard.
>>2024329
pic related
lordosis and the hottentot venus.
not necessarily sexy, but very strong sexual signaling.
>>2024331
lol.
do what works best for you. I don't know anything about the program you're working in.
I'm naught but a humble paleontologist, what you're doing is well above my paygrade.
>>2024333
My paygrade is zero, because I've recently finished highschool and I'm waiting for university, and there's no jobs available near me that would be appropriate to only spend 8 weeks in xwx
>>2024335
my paygrade is also zero.
I retired from paleontology long before digital skeletal models were a thing. Fascinating stuff though, and I enjoy talking to anyone that knows some anatomical terms of the axial skeleton.
>>2024337
My main reason for bothering to learn anatomical terms is because I want to make a catgirl model to use as a reference for RPs, since I've been RPing as a catgirl for so long that the inside of my soul probably looks like https://www.youtube.com/watch?v=gbt61vcAkG0
Speaking of which, I really need to find a way to buy nootropics without my mother finding out, since that'd be awkward even though it's not really a recreational drug and rather just to assist hallucination that can be done in other ways.
>>2024343
you just gotta learn the symptoms of ADHD and convince your doctor you have them.
I wish you luck, anyone willing to learn that much for the sake of imagination is exactly the sort we need doing science. Seriously, we all start off RP'ing and wind up in a lab. Creativity and anal attention to detail are actually a talent.
>>2024356
Pretty sure they can just be ordered online, but I'd prefer getting them in person since I can't afford a PO box.
>>2024358
sure but it seems a bit risky to break the law for something you can get perfectly legally from your doctor.
do as you like though.
>>2024359
Nootropics are illegal?
>>2024361
In the US the good ones are pretty much all only legal with a prescription.
OP here, should the arms start by attaching shoulders to the top of the thoracic and then attaching arms to the shoulders?
>>2024891
sounds right.
Doing this skeleton would be waaay easier if I knew how long each bone should be.
Also, if I knew which bones were relevant. Maybe it's worth adding chest bones for breathing?
>>2024922
Think that such a bone would effectively be the scapula?
>>2024924
>scapula?
scapula+clavicle
aka pectoral girdle
>>2024926
But the clavicle doesn't attach to the thoracic.
I would probably attach the clavicle for breathing animation, but I can't have both clavicles attaching to the breastbone.
>>2024928
Nah, I'm not saying you need a clavicle, just saying your shoulder bone would be analogous to both the clavicle and scapula together.
>>2024931
Oh my god
That picture is so useful.
But yeah, I could actually have it like that.
>>2024934
Alright, not as useful as I thought, the lack of spine stuff is a pain.
Alright, I need help with some more anatomy stuff.
Since I want a reusable topology and bone structure, I'm trying to find out how the human bone structure translates to feline and canine bone structure. It's super confusing, especially with the front and hind paw differences.
>>2026160
Anyone?
It's hard finding good sources for this.
>>2026216
it's sort of difficult to explain. google skeletal diagrams and compare.
the bones that form the back of the hand and the top of the foot have become stretched out to make another part of the leg. This arrangement is actually extremely common in tetrapods, humans are the weirdos in that regard.
we haven't turned our hands or feet into leg parts, because running was never all that important to us.
>>2026216
this comparison for example.
there's tons of them online that tell exactly which bones are the same.
>>2026216
or this.
humans are plantigrade, dogs and cats are digitigrade.
>>2026227
I've always understood that part, but there's stuff like
>>2026230
It says which sets of bones are the same, but I need to know every single matching couple of bones, as well as any bones that are added or removed.
Such as, what happens to the big toe bones? Do they disappear, and the hock is a new bone that is added on?
And are the front paws the same in terms of approximate bone structure except that the thumbs are preserved?
And would all of the above hold true for both canines and felines?
>>2026237
ah, I see.
the human thumb and big toe are analogous to the dew claw iirc, but I don't know if they're actually homologous.
the hock is the calcaneus in humans, the heel bone. All the bones of the digits should be there, I think. It should be easy to check.
the only real variation I'd expect would be in the carpus and other sesamoid bones, but I'm not sure that the difference actually matters at all.
>>2026242
What do you mean by anal and homo relationships?
And is the heel bone/hock something that would require its own bone to animate, or does it move in perfect tandem with another bone?
>>2026252
>What do you mean by anal and homo relationships?
kek
anal means they do the same thing
homo means they're the same bone
the two are anal in that they both oppose the other digits
I don't know if they're actually the same bones though.
the heel/hock always moves with the tarsus. Or tarsal bones in humans. Essentially as a solid unit.
>>2026264
Alright, thanks!
So, this applies to both felines and canines, right?
And is thing on forepaws near the wrist is just a downwards facing hock?
