Boobs start vibrating weirdly when something presses against them (like crossed arms animation)

[Krit-hit]

So in my game whenever any female character does the crossed arms animation, their boobs start... vibrating? Flailing around? Jittering? Not sure what's the right word, but it's like they're being electrified or something. It also happens when one female character presses her breasts against another's (like in OStim F/F scenes). In that case, both their boobs start doing the same thing.

 

Here's my load order: https://pastebin.com/PZpr4HEQ

 

I'm using 3BA bodies with the push-up on clothing, SMP Physics with reduced jiggle physics (I do remember messing around with the FOMOD here a few times to get the jiggle just right), XP32 Skeleton, and OBody as well. I'll add more information if necessary, but this is all that's coming to mind right now. Could anyone help me out here?

[Krit-hit]

Anyone who can help please?

[traison]

You'll most likely have to sacrifice something else, like responsive physics, if you want to fix most of the jittering. But here's some things that should reduce it:

1. Make sure the collision*minOffset and collision*maxOffset values are large enough to allow the tits to get out of the way.
2. Consider playing with the collisionElastic, collisionMultiplier, collisionMultiplierRot and collisionPenetration values.
3. Set collisionFriction to 0.

If you have c++ knowledge, then the source code of CBPC obviously gives you the keys to the city in this regard.

 

Edit: Just discovered that there's a typo in the variable name for collision multipliers: they're spelled "multipler", without the last "i". Time to reconfigure physics presets, AGAIN. 💀

Edited April 26, 2025 by traison

[Krit-hit]

2 minutes ago, traison said:

You'll most likely have to sacrifice something else, like responsive physics, if you want to fix most of the jittering. But here's some things that should reduce it:

1. Make sure the collision*minOffset and collision*maxOffset values are large enough to allow the tits to get out of the way.
2. Consider playing with the collisionElastic, collisionMultiplier, collisionMultiplierRot and collisionPenetration values.
3. Set collisionFriction to 0.

If you have c++ knowledge, then the source code of CBPC obviously gives you the keys to the city in this regard.

Where are these settings found? 3BA FOMOD? Some mod's MCM or config file?

[traison]

Those would be in the CBPConfig*.txt file that has the physics profiles that apply to the character that you're having trouble with. All CBPC files are in SKSE\Plugins. The profiles and their conditions are defined in the CBPCMasterConfig*.txt files.

[Krit-hit]

31 minutes ago, traison said:

Those would be in the CBPConfig*.txt file that has the physics profiles that apply to the character that you're having trouble with. All CBPC files are in SKSE\Plugins. The profiles and their conditions are defined in the CBPCMasterConfig*.txt files.

Ah I thought changing CBPC configs wouldn't do anything if I selected SMP physics in the 3BA settings. If I'm encountering this issue with every character instead of a specific one, I should be tweaking the CBPCMasterConfig.txt, right? 

 

P.S. Thanks for your help so far

[traison]

8 minutes ago, Krit-hit said:

Ah I thought changing CBPC configs wouldn't do anything if I selected SMP physics in the 3BA settings. If I'm encountering this issue with every character instead of a specific one, I should be tweaking the CBPCMasterConfig.txt, right?

 

You only tweak CPBC if CBPC is the one controlling the node you want to change. You need to know which system is being used before changing anything.

[Krit-hit]

12 minutes ago, traison said:

 

You only tweak CPBC if CBPC is the one controlling the node you want to change. You need to know which system is being used before changing anything.

I'm certain I picked full SMP. I would swap to CBPC but I already have some armors which depend upon SMP. Any chance you know how to tweak the settings with SMP too? 

[traison]

SMP configuration starts from inspecting all worn meshes to find which SMP presets they reference as well as inspecting the defaultBBPs.xml file to see if it has any additional ones.

 

Unfortunately I can't remember which values specifically could cause jittering in SMP as its been too long since I used it for anything other than hair and clothing. My documentation for SMP is also quite old but this is what I have in it that may be relevant:

 

Generic Constraints

• If *Bounce values are set too low (<1) it may cause jittering. This is most likely constant, not just during collisions.
• Reducing the *Stiffness values may reduce the jittering in extreme situations, as there would be less energy pulling on things.

Shapes

• Consider adjusting the penetration values on the affected shapes.
• "prenetration" despite looking like a typo has been coming and going in the SMP code. My latest notes suggests it may be used again in the more recent SMP variants, and that it now functions a bit like a margin when given a negtive value. May be worth adjusting as well.

Bones

• Adjust friction, rollingFriction and restitution.
• *Damping may reduce it, but would also make movement overall very sluggish if increased.

configs.xml

• solver.numIterations may improve collision accuracy if increased.

 

That's probably what I'd start with, but one thing to keep in mind here is that I've been adjusting CBPC for years now. Finding something that is both fast (i.e. not "balloon tits"), responsive and not glitchy is very difficult and very much depends on:

1. Your current FPS and overall game performance.
2. The weightpainting on the body you're using.
3. The animations you're using, and what the motion is like in them. Think resonating frequency for instance.

Edited April 25, 2025 by traison

[Krit-hit]

Okay I tested it with both CBPC and SMP, turns out I didn't have SMP on the NPCs, so it was indeed a CBPC bug (it looks even worse with SMP lol, the boobs just get completely squished down by the crossed arms). I need to find a way to fix this in CBPC. 

 

I also made a clip of the bug, if it can help someone track down the problem better. Has anyone seen anything like this before? 

[Krit-hit]

1 minute ago, traison said:

SMP configuration starts from inspecting all worn meshes to find which SMP presets they reference as well as inspecting the defaultBBPs.xml file to see if it has any additional ones.

 

Unfortunately I can't remember which values specifically could cause jittering in SMP as its been too long since I used it for anything other than hair and clothing. My documentation for SMP is also quite old but this is what I have in it that may be relevant:

 

Generic Constraints

• If *Bounce values are set too low (<1) it may cause jittering. This is most likely constant, not just during collisions.
• Reducing the *Stiffness values may reduce the jittering in extreme situations, as there would be less energy pulling on things.

Shapes

• Consider adjusting the penetration values on the affected shapes.
• "prenetration" despite looking like a typo has been coming and going in the SMP code. My latest notes suggests it may be used again in the more recent SMP variants, and that it now functions a bit like a margin when given a negtive value. May be worth adjusting as well.

Bones

• Adjust friction, rollingFriction and restitution.
• *Damping may reduce it, but would also make movement overall very sluggish if increased.

configs.xml

• solver.numIterations may improve collision accuracy of things if increased.

 

That's probably what I'd start with, but one thing to keep in mind here is that I've been adjusting CBPC for years now. Finding something that is both fast (i.e. not "balloon tits"), responsive and not glitchy is very difficult and very much depends on:

1. Your current FPS and overall game performance.
2. The weightpainting on the body you're using.
3. The animations you're using, and what the motion is like in them. Think resonating frequency for instance.

Thank you, that's really in-depth! I'll investigate some more. I also shared a clip of the bug too, could you take a look at it and see if it's something you've seen before? It seems we both posted at the same time haha

[traison]

38 minutes ago, Krit-hit said:

I also shared a clip

 

Personally I wouldn't fix that, but if I had to try to do something about it, I'd reduce the radius (R) of the boob collision shapes by maybe 0.5 units. These are defined in the CBPCCollisionConfig*.txt file that applies to your character. The conditions, if there are any, are defined at the top usually. The format for collision spheres is:

 

X,Y,Z,R

 

Edit: Or increase the collisionPenetration by 0.05-0.1 in the relevant CBPConfig*.txt file.

Edited April 25, 2025 by traison

[Krit-hit]

Thanks, I'll give it a shot!

[Grey Cloud]

21 hours ago, Krit-hit said:

their boobs start... vibrating? Flailing around? Jittering? Not sure what's the right word,

I opt for "fluttering".  🧐

[Krit-hit]

1 hour ago, Grey Cloud said:

I opt for "fluttering".  🧐

Haha that sounds fitting too. I actually asked the mod author and they seem partial to "jittering" themselves. 

 

Here's what they had to say about fixing the issue, I'll share it just in case someone else is having the same problem:

 

Quote

This is caused by a combination of the animation putting the hand/arm colliders right inside the breasts triggering constant collision response and your bounce config settings not allowing the collision responses to happen because of the movement limits.

From the FAQ Article and the sticky:

You can try adjusting .collisionFriction values in your CBPConfig****.txt files to be higher. Default is 0.80. If you have lower values, you can set it higher, up to 1.0 (which disables bounce during collision and should fix the jitters completely).
Also make sure .collisionElastic is set to 1 which fixes these types of jitters when a .collisionFriction value lower than 1.0 is used.

So, there are two solutions:
- You can either adjust (or use a) bounce configs to allow breast movement that would make the breasts to escape the collision when a collision response is triggered
- Or you can disable friction completely (or reduce it a lot) which stops bounce when a collision occurs.

I suggest the latter because if the jitters bother you, the easiest way is to get rid of them completely instead of making the breasts stretch out of the way.

Alternatively, there is an optional bounce config in the optional section that works for 3 bone breast bodies like 3BA/BHUNP that has collisionFriction set to 0.8 already and allows more stretching for breasts. You can try that to see if that's better for you or not.

I suggest opening all the breast related CBPConfig****.txt files in CBPC and your body mod(3BA/BHUNP etc.) and setting 
- .collisionFriction to a value between 0.8 - 1.0 (If it's lower than 0.8, set it to 0.8 and try, if it's already 0.8, you can try setting it up to 1.0)
- .collisionElastic to 1

Note that you need to make this changes in the winning files. If you are using 3BA/BHUNP etc. they come with CBPConfig_3b.txt file where you need to do this change.

Next version of the mod 1.7.0 will hopefully have more fixes in the code to prevent this kind of collision jitter from happening even with .collisionFriction set to lower than 1.

 

[traison]

Just discovered that there's a typo in the variable name for collision multipliers: they're spelled "multipler", without the last "i". Time to reconfigure physics presets, AGAIN. 💀

 

I edited my previous post for future Googling people.