wip Real-Time Body Physics (DirectX 11)

[APassingGhost]

14 hours ago, CPVC said:

 

Hmmm, ok. Well, new compiler, new problems, I guess. Does your log file say anything when it freezes? Mind sharing it? It's possible a swich to Clang is a step in the wrong direction. I just wanted to see if it improved anything for those that were having problems and see if there were other benefits. In my testing, it seems to be more stable.

 

 

It is fixed. Down should always be down regardless of orientation, but the coordinates I was using for linear physics are incorrect. I need to redo them with what I learned implementing angular physics. Try using the direct translation of the breast bones for linear physics calculations. Enable the debug flag "testAltBreastPhysics1". I'll get them working exactly as they should for the next release.

 

 

As of right now, I am unable to replicate the problem? I have a log file, but the log file is only from my most recent attempt to replicate this issue. I'm not sure if it's much help, but I'll provide it anyway

 

Note: I've modified it to remove my name, as I prefer to stay anonymous.

Log.txt

[APassingGhost]

Addendum: I only had to try and replicate the issue because I downgraded to the earlier build and have been playing on that since yesterday. Apologies.

[APassingGhost]

Update: By some...miracle? The error managed to happen again. Here's my log file for reference: Log.txt 

[asdurgico]

I tested the new Clang version for half an hour and i didn't have any CTD, before i was getting a lot of crashes so at least for me this version is much better!

[jeno3]

The Clang version doesn't work for me. The game loads up to the home screen, but when I try to load a household, it crashes. I am currently playing the game in windowed mode; perhaps that has something to do with it. However, if it works for some people but not for others, it might be a good idea to offer two different versions.

[CPVC]

21 hours ago, jeno3 said:

The Clang version doesn't work for me. The game loads up to the home screen, but when I try to load a household, it crashes. I am currently playing the game in windowed mode; perhaps that has something to do with it. However, if it works for some people but not for others, it might be a good idea to offer two different versions.

 

I could do that, but it would be nice to standardize on one compiler if I can. Make sure to submit error reports when it crashes.

[jeno3]

On 5/12/2026 at 2:45 AM, CPVC said:

t is fixed. Down should always be down regardless of orientation, but the coordinates I was using for linear physics are incorrect. I need to redo them with what I learned implementing angular physics. Try using the direct translation of the breast bones for linear physics calculations. Enable the debug flag "testAltBreastPhysics1". I'll get them working exactly as they should for the next release.

 

I tried it with "testAltBreastPhysics1." Unfortunately, that didn't change anything. However, it is interesting to observe: the more the legs are bent, the more the breasts pull in that direction. When the Sim is lying on their stomach, with their legs stretched out, straight the breasts move toward the floor; in this case, "down" actually means down. I hope you manage to fix this. Thanks for everything!

[Quabn]

I really like this mod but I'm having a problem with the DX11 version.

 

The game always become unresponsive when I use DX11 version, even after removing all mods, it's still the same problem. I tried waiting it out and the problem still persist forcing me to close it.

 

The game run fine with DX9.

 

[CPVC]

16 hours ago, Quabn said:

I really like this mod but I'm having a problem with the DX11 version.

 

The game always become unresponsive when I use DX11 version, even after removing all mods, it's still the same problem. I tried waiting it out and the problem still persist forcing me to close it.

 

The game run fine with DX9.

 

 

Hmmm. Mind sharing your log file? I'll take a gander at it and see if I can figure out what's up.

[Quabn]

2 hours ago, CPVC said:

 

Hmmm. Mind sharing your log file? I'll take a gander at it and see if I can figure out what's up.

Here ya go

 

I did went back to DX9, do I need to do another DX11 again play to generate new log tho for the problem?

 

I run the game with DX11 again and generated another log, just to be sure.

Log.txt

Log - DX11.txt

Edited May 23 by Quabn

[CPVC]

20 hours ago, Quabn said:

Here ya go

 

I did went back to DX9, do I need to do another DX11 again play to generate new log tho for the problem?

 

I run the game with DX11 again and generated another log, just to be sure.

Log.txt 12.52 kB · 1 download

Log - DX11.txt 20.79 kB · 1 download

 

Yes the DX11 version was needed, thanks for getting that. I don't see anything off in your log. It looks like everything is working until a new input layout is detected and it locks up. Here is a build made with a different compiler. Try this out and see if it works.

 

RTBP v2.3~1 2026-05-23 (MinGW).zip

 

jeno3, here's a MinGW build of the latest version. It might work for you, too.

 

On 5/15/2026 at 3:08 AM, jeno3 said:

The Clang version doesn't work for me. The game loads up to the home screen, but when I try to load a household, it crashes. I am currently playing the game in windowed mode; perhaps that has something to do with it. However, if it works for some people but not for others, it might be a good idea to offer two different versions.

 

[Quabn]

28 minutes ago, CPVC said:

 

Yes the DX11 version was needed, thanks for getting that. I don't see anything off in your log. It looks like everything is working until a new input layout is detected and it locks up. Here is a build made with a different compiler. Try this out and see if it works.

 

RTBP v2.3~1 2026-05-23 (MinGW).zip 6.31 MB · 1 download

 

jeno3, here's a MinGW build of the latest version. It might work for you, too.

 

 

So I tried the MinGW build and it's the same problem, game freeze and become unresponsive. I taken off every mod except 'RTBP Mod' folder ofc then try again on vanilla and it's still the same (I also delete the localthumbcache.package just to be sure). I'm going to leave both Vanilla and Modded log file here and keep on trying with some tweak like lower the graphics.

Log - Modded.txt Log - Vanilla.txt

[CPVC]

1 hour ago, Quabn said:

So I tried the MinGW build and it's the same problem, game freeze and become unresponsive. I taken off every mod except 'RTBP Mod' folder ofc then try again on vanilla and it's still the same (I also delete the localthumbcache.package just to be sure). I'm going to leave both Vanilla and Modded log file here and keep on trying with some tweak like lower the graphics.

Log - Modded.txt 20.24 kB · 0 downloads Log - Vanilla.txt 21.15 kB · 0 downloads

 

Hmmm, something to do with copying the vertex and index buffers back to the GPU after analyzing and modifying... Try this build here. This is a "read-only" build of RTBP. Vertex and index buffers won't be modified and written back to the GPU and butt simulators are disabled. It might work. You'll need to manually install the DLL. Just copy the new one over the old one in your "...\The Sims 4\Game\Bin\" folder.

 

RTBP 2.3~1 2026-05-23 (Read Only).zip

[Quabn]

2 hours ago, CPVC said:

 

Hmmm, something to do with copying the vertex and index buffers back to the GPU after analyzing and modifying... Try this build here. This is a "read-only" build of RTBP. Vertex and index buffers won't be modified and written back to the GPU and butt simulators are disabled. It might work. You'll need to manually install the DLL. Just copy the new one over the old one in your "...\The Sims 4\Game\Bin\" folder.

 

RTBP 2.3~1 2026-05-23 (Read Only).zip 1.55 MB · 0 downloads

Nope, still the same problem.

 

i'm gonna try to completely reinstall the game to check.

Log - Read Only Butt simulator Off.txt

[Quabn]

Hello I'm back with the same problem after reinstalling the game

 

I tried the stable DX11 version first then the MinGW build and the Read only build

 

All result in the same problem 

Log - MinGW.txt Log - Read Only.txt Log - stable DX11.txt

[CPVC]

11 hours ago, Quabn said:

Hello I'm back with the same problem after reinstalling the game

 

I tried the stable DX11 version first then the MinGW build and the Read only build

 

All result in the same problem 

Log - MinGW.txt 21.22 kB · 0 downloads Log - Read Only.txt 13.97 kB · 0 downloads Log - stable DX11.txt 22.57 kB · 0 downloads

 

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.

[Quabn]

6 hours ago, 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.

Oh, one question.

 

Does playing in Fullscreen\Borderless mode affect anything?

[jeno3]

On 5/24/2026 at 2:06 AM, CPVC said:

jeno3, here's a MinGW build of the latest version. It might work for you, too.

I just tested it. It runs stably.

[0Spirit0]

15 hours ago, Quabn said:

Oh, one question.

 

Does playing in Fullscreen\Borderless mode affect anything?

I only got this mod working well in windowed and borderless mode

 

Spoiler

 

 

Edited May 25 by 0Spirit0

[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.