# Real-Time Body Physics (RTBP) by CPVC

### Version v2.3.1~3 - 2026-08-18

# Disclaimer

Play with this at your own risk. I recommend you back up your save files or start a new throw-away game before trying it. I am not liable for any damage this mod does to your computer.

# Installation

1. Move "d3d11.dll" to "...\[TS4_INSTALL_DIR]\Game\Bin\". It should be in the same directory as "TS4_x64.exe". Currently, this mod only works with the 64 bit version of The Sims 4.
2. Move "RTBP" to "...\[MY_DOCUMENTS]\Electronic Arts\The Sims 4\". This directory will house your settings file and log file once it is generated.
3. Copy the folder "RTBP Mod" to "...\[MY_DOCUMENTS]\Electronic Arts\The Sims 4\Mods\".
4. ReShade: Newer versions of ReShade no longer conflict with RTBP. Install RTBP first, then install ReShade. That's it.

# RTBP GUI

Press F11 to open the RTBP GUI. The GUI can be used to configure RTBP without dirtying your hands manually editing settings files.

# Settings

It is recommended that you use the RTBP GUI to modify your settings. It's easier and you can see your changes in real time.

The settings file, located at ...\[MY_DOCUMENTS]\Electronic Arts\The Sims 4\RTBP\Settings.ini" can be modified to change the behavior of the mod.

The section "rtbp.general" is for general settings of the mod, like if you want to start the debug command server or if you want to enable/disable breast and butt physics.

The section "rtbp.leftBreast" sets the settings that control the spring physics of the left breast. If you don't know what these settings do, please read the next section "Simulation Settings".

I think the rest is self-explanatory.

# Advanced Settings: Debug Flags

You can skip this section if you don't want to mess around with debug flags. Most people probably won't.

Debug flags can be set in your settings file, but they're a special case compared to other settings. Debug flags need to be explicitly defined to make them persist in your settings file. When saving your settings file, your "[rtbp.debugFlags]" section will be transfered over, but any debug flags you set using the Commander or through manually entering commands will not be written to your settings file.

This is for safety. Debug flags should not be taken lightly. Testing out alternate breasts and butt physics modes is usually ok, but some debug flags can crash your game or worse. Debug flags need to be tested first, but do this at your own risk. If you like what they do and everything is stable, you may enable debug flags in your settings file.

The default value for every debug flag is "false". As soon as a debug flag is referenced in RTBP, it will be defined and will show up in the commander. If you add an entry to your "[rtbp.debugFlags]" section, but set the value to "false", the entry will be completely ignored.

Debug flags are subject to change and you cannot rely on them working the same way or even existing across different versions of RTBP.

# Simulation Variables

RTBP is based off spring physics. The following settings can be modified through the GUI or by editing the settings file.

## Linear

- Mass mass: The mass of the simulated object in kilograms. Controls how resistent to change the object is. "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
- Damping damping: Damping controls the speed in which the movement slows and finally comes to a stop. Kinda like friction on the spring. Higher values bring moving objects to rest faster.
- Spring K springK: The springK constant defines the spring characteristics of the simulation. Basically how elastic the spring is and how it will respond when force acts upon it. Google "Hooke's Law" for more information. Higher values will make the spring act more springy.
- Power power: Power is is the multiplier for the force that acts on the simulations. At "1.0" the force is unchanged. "2.0" is double, "0.5" is half. I don't recommend playing with this one. I put it in for debugging purposes and will probably remove it in the future.
- Gravity gravity: Gravity is the gravity constant of the simulations, a constant downward force acting on the springs in meters per second. "9.80665" is the gravity of earth. RTBP assumes every sim is 1.7272 meters tall, or 5'8". Higher gravity levels will will make everything sag much more. I wouldn't play with this one either, unless you'd like to pretend your sims live on another planet or if they're training to fight Cell or something.
- Min (X|Y|Z) min(X|Y|Z): The maximum distance a simulator can deviate from it's target in the negative (X|Y|Z) axis.
- Max (X|Y|Z) max(X|Y|Z): The maximum distance a simulator can deviate from it's target in the positive (X|Y|Z) axis.

## Angular

- Angular Mass angularMass The angular counterpart to linear mass.
- Angular Damping angularDamping: The angular counterpart to linear damping in radians per second.
- Angular Spring K angularSpringK: The angular counterpart to linear spring K in radians per second.
- Angular Gravity angularGravity: The angular counterpart to linear gravity.
- Min (X|Y) angularMinX: The maximum difference a simulator can deviate from it's target orientation in negative degrees.
- Max (X|Y) angularMaxX: The maximum difference a simulator can deviate from it's target orientation in positive degrees.

# Postscript

Thank you for helping me develop RTBP through your bug reports, suggestions, and other feedback.

This file has been automatically generated. Please let me know if there are any mistakes. Thanks!