wip Real-Time Body Physics (DirectX 11)

[runitup]

hey so i'm using the dx11 version and it's working but the breasts and butt get kinda wonky even when standing still sometimes, is there any settings tweaking you would recommend?

 

also i'm not sure if it's related to rtbp or not but i've noticed some of the clothes my sims wear will be stretched out at the butt area 

Edited May 29 by runitup

[CPVC]

On 5/29/2026 at 5:14 AM, runitup said:

hey so i'm using the dx11 version and it's working but the breasts and butt get kinda wonky even when standing still sometimes, is there any settings tweaking you would recommend?

 

also i'm not sure if it's related to rtbp or not but i've noticed some of the clothes my sims wear will be stretched out at the butt area 

 

Lower the spring k value to make the simulators less twitchy if that's the issue. I only use angular physics for breasts, so I'm not sure what a good setting for linear would be. Using both linear and angular at the same time might be a bit much. You might want to just stick with one or find a balance between the two.

 

The sagging butt issue is a known problem. There is hard coded limit in the vertex shader on how many bones a sim may have, but in experiments, I have successfully edited the bytecode of a shader at runtime, so I may be able to increase that limit, but more research is needed.

[jeno3]

Hi CPVC,

 

I’m using the latest version, which runs great and is stable. I’m also experiencing the issue where the breasts sometimes jiggle uncontrollably or too vigorously. I managed to get a pretty good handle on this in-game, though it does require a bit of trial and error. The best approach is to adjust the movement using the Min and Max settings; if you get the configuration right, you can even use linear and angular movement together.

 

However, I’ve run into another problem now. The way the animated size of the area is calculated must have changed—or perhaps I made a mistake. I’ve attached my latest work here; only the shoulders move, while the breasts remain still. It would be helpful if you could mark which vertices I shouldn't alter, or perhaps see if there are other solutions.

 

They aren't quite finished yet, but the basic shape is there. I want to make the breasts look rounder and more natural on the inner side, facing the body. But I don't think that should be a problem.

 

Saggy_310526.rar

[jeno3]

7 minutes ago, jeno3 said:

I’m using the latest version, which runs great and is stable. I’m also experiencing the issue where the breasts sometimes jiggle uncontrollably or too vigorously. I managed to get a pretty good handle on this in-game, though it does require a bit of trial and error. The best approach is to adjust the movement using the Min and Max settings; if you get the configuration right, you can even use linear and angular movement together.

Oh, I should add that you need to configure the min and max settings for each coordinate. For example: set the minimum and appropriate maximum for Linear X, and do the same for Y and Z. Do the Same for Angular.

When combining linear and angular movement, it’s best to set the gravity to 0 for the angular physics; in my case, the higher the gravity setting, the more the breasts get pulled into the body.

[CPVC]

19 hours ago, jeno3 said:

Hi CPVC,

 

I’m using the latest version, which runs great and is stable. I’m also experiencing the issue where the breasts sometimes jiggle uncontrollably or too vigorously. I managed to get a pretty good handle on this in-game, though it does require a bit of trial and error. The best approach is to adjust the movement using the Min and Max settings; if you get the configuration right, you can even use linear and angular movement together.

 

However, I’ve run into another problem now. The way the animated size of the area is calculated must have changed—or perhaps I made a mistake. I’ve attached my latest work here; only the shoulders move, while the breasts remain still. It would be helpful if you could mark which vertices I shouldn't alter, or perhaps see if there are other solutions.

 

They aren't quite finished yet, but the basic shape is there. I want to make the breasts look rounder and more natural on the inner side, facing the body. But I don't think that should be a problem.

 

Saggy_310526.rar 1.79 MB · 0 downloads

If you can remove the clavicle bone influence from the upper part of the breasts, that ought to work. As for the breasts jiggling out of control, I haven't experienced that ever. Any way you can share a video of that happening?

 

Edit: The first ray starts at 0.088, -1.0, 1.4 and goes in direction 0.0, 1.0, 0.0. It should intersect this triangle:

 

Edited June 6 by CPVC

[jeno3]

7 hours ago, CPVC said:

If you can remove the clavicle bone influence from the upper part of the breasts, that ought to work. As for the breasts jiggling out of control, I haven't experienced that ever. Any way you can share a video of that happening?

 

Edit: The first ray starts at 0.088, -1.0, 1.4 and goes in direction 0.0, 1.0, 0.0. It should intersect this triangle:

 

Yes, of course. Attached a Video. 

 

Thanks for the quick reply.

It would be better if I didn't have to change that, but only if it's feasible. I can't seem to get the vertices back to their original position, either.

[jeno3]

Jiggle_Shoulders2026-06-06 14-33-52-871.rar

[Reddud3]

On 5/24/2026 at 11:45 PM, CPVC said:

 

Well, darn. It does look like there's a pattern here, which at least points me in the right direction. When it freezes it's almost always related to the copying of buffers. I'll try to improve the debugging around that and see if I can get more information on what's going on. In the mean time, I'm afraid you are stuck with DX9 version. Sorry about that.

I'm experiencing the same issue. I've been having this issue on older versions too. I'm not sure I've ever been able to use the DX11 version, as I keep crashing when entering CAS after clicking 'edit household'. I've sent three crashes via the error reporter, one for the latest Clang version, the MinGW build and the read-only version. Hope they help!

[Overdraft0213]

Already 15 mins in the game and the logo isn't disappearing for me somehow. It happens randomly, really, sometimes it does dissapear and sometimes it doesn't


I have already set the RTBP logo to off in the settings

[CPVC]

4 hours ago, Overdraft0213 said:

Already 15 mins in the game and the logo isn't disappearing for me somehow. It happens randomly, really, sometimes it does dissapear and sometimes it doesn't


I have already set the RTBP logo to off in the settings

 

Yeah, I did some refactoring before this release and messed something up. Just leave "Show RTBP Logo At Startup?" checked for the time being and it will go away after 5 seconds. Sorry about that. It'll be fixed in the next experimental release.

[yty001]

excuse me how can i solve this problem?

日誌.txt

Edited June 12 by yty001

[CPVC]

9 hours ago, yty001 said:

excuse me how can i solve this problem?

日誌.txt

 

This is a known issue related to scaling the GUI. If the window size is too small, ImGUI, the UI library I'm using, is unable to render. I guess for now, don't let the window get too small. I'll come up with a fix that prevents this from happening in the future.

[yty001]

2 hours ago, CPVC said:

 

這是一個已知的與圖形使用者介面縮放相關的問題。如果視窗尺寸太小，我使用的使用者介面庫 ImGUI 就無法渲染。所以目前來說，最好不要讓視窗尺寸太小。我會盡快找到解決方案，防止將來再次出現這個問題。

thank you

[CPVC]

There is a possibility that this build here might work for those of you that are having trouble getting RTBP to work. I've studied other projects that work similarly to RTBP and found that they all export about 40 functions that have been unavailable in RTBP so far. I've made them available as proxy functions that simply pass through RTBP to the system d3d11.dll. This could work or at least help. If you're having issues, please try this out and let me know if it works or not. This is just the DLL, so you will have to manually install.

 

RTBP v.2.3~2 2026-06-12 (Forward Functions).zip

[APassingGhost]

11 hours ago, CPVC said:

There is a possibility that this build here might work for those of you that are having trouble getting RTBP to work. I've studied other projects that work similarly to RTBP and found that they all export about 40 functions that have been unavailable in RTBP so far. I've made them available as proxy functions that simply pass through RTBP to the system d3d11.dll. This could work or at least help. If you're having issues, please try this out and let me know if it works or not. This is just the DLL, so you will have to manually install.

 

RTBP v.2.3~2 2026-06-12 (Forward Functions).zip 1.57 MB · 1 download

I tried the new build and uhhh loading up one of my households caused the game to instantly close itself

Log.txt

I'll look more into it next week after my assignments but in the meantime, here's my log if that tells you anything

[CPVC]

6 hours ago, APassingGhost said:

I tried the new build and uhhh loading up one of my households caused the game to instantly close itself

Log.txt 5.65 kB · 0 downloads

I'll look more into it next week after my assignments but in the meantime, here's my log if that tells you anything

 

Thanks for testing it. I have made arrangements to test RTBP on other machines so hopefully I can get to the bottom of why it works on some machines and not others.

[yokozii]

Ive been away awhile , saw the patreon update for the new build. excited to try it once I update my game 

[shinichi104]

33 minutes ago, yokozii said:

Ive been away awhile , saw the patreon update for the new build. excited to try it once I update my game 

SO glad to hear from you!!!! glad you are doing ok!!

[APassingGhost]

17 hours ago, CPVC said:

 

Thanks for testing it. I have made arrangements to test RTBP on other machines so hopefully I can get to the bottom of why it works on some machines and not others.

 

Yeah no it's definitely something of RTBP - Tried with a different household and the game force quit again unfortunately

[CPVC]

7 hours ago, APassingGhost said:

 

Yeah no it's definitely something of RTBP - Tried with a different household and the game force quit again unfortunately

 

Bummer. Well, worth a shot I guess. Like I said in my earlier post, I'm going to be testing RTBP out on some other machines soon. Just waiting on the machines being available.

[jeno3]

Hi,

 

my Game crashed with the Version (Forward Functions). First it runs, but after a view minutes....Game Over

Log.txt

[jeno3]

But there’s something else, too. Please take a look at this video. It’s the linear physics causing this, not the angular ones. The larger the breasts, the worse it gets. Maybe you can get a handle on that? Otherwise, I’ll look forward to your next experiment, which sounds very promising. I hope everything works out the way you—and all of us—hope it will. I’m glad you’re staying so dedicated to this.

bandicam 2026-06-17 12-14-52-135.rar

[CPVC]

17 hours ago, jeno3 said:

But there’s something else, too. Please take a look at this video. It’s the linear physics causing this, not the angular ones. The larger the breasts, the worse it gets. Maybe you can get a handle on that? Otherwise, I’ll look forward to your next experiment, which sounds very promising. I hope everything works out the way you—and all of us—hope it will. I’m glad you’re staying so dedicated to this.

bandicam 2026-06-17 12-14-52-135.rar 55.89 MB · 1 download

 

The "forward functions" variant is a little wonky. It's based on my work in progress code and I've probably screwed up the matrix multiplication order again. I'll fix it and release a new build with the forwarded functions if it's actually helping.