Rigging Help - Compound Bow

[cedar tangle]

Need to rig this compound bow game asset im creating for my portfolio.
If you ahve any tips or cool tutorials that might be usefull id appriciate it. (im very new to rigging)
I cant figure out how to go about it. I need the main string to move around the cams(Top/Bot gears) when u pull the string from the middle. The cams(Gears) will turn as u pull the string/arrrow backwards. I tried to figure out an IK-Spline setup but had no luck.

[velvet tangle]

you coud try with shapekeyes?

[cedar tangle]

i should add that im very new to rigging, so if u got basic tutorials that might explain what u mean that would be greatly appriciated.

[velvet tangle]

have the "default state" as the base, then create shapekeyes for the bending rope (idk how it is called again) and then create shapekeyes for rotating the gears

[cedar tangle]

shapekeys similar to blendshapes?

i have rigged a bit in maya but nothing mechanical.

[velvet tangle]

https://youtu.be/YDu6y_2jFg0?si=FtUQYEQ2anmEmznj

haven't watched the full vid, but it covers a lot of topics what shapekeyes can do

[cedar tangle]

ty ill look into it

[velvet tangle]

not sure if shapekeyes is the most efficient way of doing your animation but I think it's gonna be the easiest one

[cedar tangle]

would this work as a "skeletal" mesh in unreal

or is this blender specific, seems almost like u creating an alembic

[velvet tangle]

I have no clue about unreal, but you can bake your shapekeyes to keyframe animations

which afaik can be used in unreal

I think

[cedar tangle]

yea, alembics are just kinda heavy compared to skeletal meshes with animated rigs, afaik. but im kinda tip toeing doing an alembic instead bcs my focus aint necesarily rigging 🙂

[velvet tangle]

maybe someone else might have a different way.

[cedar tangle]

ah shapekeys are blendshapes.

i mean its kind of a nice way to do it tho.

and im not rly gonna implement it super functionally anyways 🙂

thanks for the tip, ill try and fiddle with that for now 🙂

[velvet tangle]

You only need to make shapekeyes for the outer frames, for example wen you pull the string backwards create a shapekeye when the string is furthest away, normally when you shoot the string will go a bit further then the resting position that's where you will need to create another shapekeye. as for the gears, just gotta create one shapekeye where 1 is that they turn 360degrees

shouldn't be that hard tbh, just a fair bit of time fideling around

[velvet tangle]

glad I could help

[cedar tangle]

afraid of the string not rly smoothly following the gears, but ill give it a go

[velvet tangle]

you will have to keyframe the shapekeyes for the gears on the correct timings

[cedar tangle]

would u ad shapekeys between eachother to sort of dictate the way the string deforms?

like the absolute shapekeys i guess

[velvet tangle]

I personally would just make shapekeyes to the far ends, one for completely pulled and one where the string is bouncing past the resting point, you can set keyframes on 0.9 or something if you want a precise movement in your animation

with shapekeyes you basically have 0% being the default state or 100% being the active state, shapekeyes will interpolate between them and you can make keyframes at any stop you want. (if the terms default state and active state confuse you my appologies, have been doing figma (webdesign) all week long and they're used there)

[cedar tangle]

i dont think im quite understanding the method u r describing, it sounds very simple and relatively easy adn quick, but i cant for the life of me figure it out.

[velvet tangle]

my drawing is bad ik, but the k stands for where to make the shapekeye approxomatily

[cedar tangle]

i mean if the string just needed to bend it would be easy, but it rotates and wraps around the gear.

so it needs to unravel from the gear and then bend, and the shapekeys dont rly follow the gear

[velvet tangle]

I think you will need drivers for that, and I am not familiar with those

[cedar tangle]

trying to animate it using a custom lattice and a ton of absolute shapekeys right now :l

bcs im in caveman mode

[velvet tangle]

sorry, might have misunderstood your question at first.

[cedar tangle]

its aight, still think im getting closer and learning some 🙂

[velvet tangle]

I think combined with shapekeyes and drivers you could do it faster, but you'ill have to learn those as well then. you could bind your shapekeye to the rotation of the gears. I have asked a person to help you out further cuz this is an area I am really not familiar with. (not sure if he knows drivers as well, but he might know a better solution to animate it then I had)

[cedar tangle]

nice, and thanks. ill continue with the wacky method i have till something smarter shows up

[polar cape]

@cedar tangle @velvet tangle I think I found the solution. Ill try to explain it somehow by recording a small video

[velvet tangle]

IK rig with empty parented to the top bone?

[velvet tangle]

Did you changed the stiffness or something to keep the bones in the rotate form? Also can he export this for unreal? Cuz that was his plan iirc. (I am not familiar with unreal at all)

[polar cape]

stretch and track to constrains with drivers

I am trying to record the video but its 11pm and I am just yapping 😄

3rd try. I got this

[velvet tangle]

I am yapping all the time, and I am tired af due to many late hours working for school...

[polar cape]

https://youtu.be/RWE7DebUoO0
YouTube might take a while to convert it to FullHd

Here are all the driver expressions that I used:

For the spool / rotating bit:
((225/2.75*var)*pi/180) if ((225/2.75*var)*pi/180) > 0 else 0
225 is your max rotation and 2.75 the maximum pull distance of the empty (makes sense once you see the video)

For the track to constrain influence:
0 if var <= y else 1
y is the x position of the empty where the bone stops rotating towards it and follows the shape of the spool. So insert an value for y. Each bone needs a different y.

I have also included the .blend file so I hope it helps. I've tried to explain it as best as I can, but it's midnight so both my English and my explaining skills are at their worst. Feel free to ask if you are struggling with any bit

[polar cape]

For me, it's generally helpful (0 preparations for presentation and it works out), but not when I'm trying to explain driver functions that look like the ones shown above. If you've never worked with drivers before, it's a lot, and not finding the right words doesn't help with understanding.

Btw the model is really cool and making a rig for a bow was a lot of fun. I love those small but challenging problems and it really helps in improving 👌 Make sure to share the finished result

[velvet tangle]

Ye mb, I to do this sometimes/often jumping in to help to fast.

[polar cape]

I think you have misunderstood me. It's often very helpful to have a second pair of eyes looking at a problem, even if they're not sure if an approach will work.
What I mean is that I just have trouble conveying “complex” information when I speak English, and I'm a bit annoyed by it, which is why I started the recording 4 times 😄

[velvet tangle]

Oh got it, ye I did misunderstood you xd. Well what I said still stands tho.

[polar cape]

Dont worry about it

[velvet tangle]

To tired to worry about anything else then school+ side projects lol

[cedar tangle]

This is so cool, thanks so much. I'll try this out for sure. Just woke up so it seems super techie but I'm sure it will make sense in an hour or two 🙂
Thanks again 🙏 seemed very in depth 🙂

[cedar tangle]

Thanks man, and ofc ill make sure to share 🙂

[cedar tangle]

im having a hard time understanding the order u do the things in

Like when u add the gear driver, so it doesn't invert the intended function :/