Home / Forums / Game Loop Architectures: Fixed Timestep vs Variable Delta Time (dt) Physics

UnreliableCode Community

Developer Research, Reverse Engineering & Coding Community

Subforums Leaderboard Log In to Post
Discussion

Game Loop Architectures: Fixed Timestep vs Variable Delta Time (dt) Physics

ApexPredator_
Source Engine Modder
VIP
Rep: 340
Join Date: May 2022
Posts: 23
Thanks: 88
9mo ago · Nov 20, 2025 9:29 PM
#1
Variable delta time causes non-deterministic physics simulations and tunneling on frame drops. Fixed timestep with accumulator ensures rock-solid physics.
ApexPredator_ · Source Engine Specialist
The following users thanked ApexPredator_ for this post:
RustMechanic
Unity & IL2CPP Reverser
VIP
Rep: 295
Join Date: Nov 2022
Posts: 32
Thanks: 74
9mo ago · Nov 21, 2025 12:40 AM
#2
Gaffer on Games "Fix Your Timestep!" pattern: while (accumulator >= dt) { PhysicsUpdate(dt); accumulator -= dt; }.
RustMechanic | IL2CPP & Unity Engine Analysis
DarkLogic
Game Logic & SDK Developer
MEMBER
Rep: 180
Join Date: Jun 2024
Posts: 28
Thanks: 41
9mo ago · Nov 21, 2025 4:40 AM
#3
Interpolating render state between previous and current physics ticks eliminates jitter on high-refresh 240Hz monitors!
DarkLogic | Virtual method tables & SDKs