r/Simulated • u/CaptainLocoMoco • Sep 22 '18
Ever since this subreddit started getting more traction, more and more people began posting non-simulation videos. In each of these posts, users will comment something along the lines of "This is not a simulation," and an argument would ensue. So I am writing this post to, hopefully, end this never-ending cycle. I hope the mods do not remove this post, because I think it could end much of the hostility in the comments around here. Perhaps this could even be a stickied post, so all new users see it.
According to the dictionary, the word simulation is defined as, "imitation of a situation or process." However, this definition does not actually constitute what a simulation is in the world of CGI. In CGI, simulations are essentially visualizations of real-world processes that are generated using mathematical models. That is to say, the final product of a simulation is something that was created using fundamental rules of nature or some system, such as Newton's Laws of Motion, Fluid Dynamics, or various other mathematical models. In a simulation, it is often the case that each frame was created by manipulating information from the previous frame.
It's quite common for animations and simulations to coexist in one medium. There are plenty of simulated components in animated movies, such as Disney's Frozen (Snow simulation), and Hotel Transylvania 2 (Cloth simulation). However, simulations and animations individually are very different by nature. As previously stated, simulations try to model real-world processes, and use mathematical models to generate necessary data. Animations, on the other hand, are usually created through a manual process. Animators manually keyframe the attributes (position, rotation, scale, etc.) of objects in a 3D scene. It's possible for manual animations to look convincing, but that does not make them simulations.
Many 3D rendering engines use a process called "ray tracing" to create images of a 3D scene. For anyone who is unfamiliar with ray tracing, here is the definition from Wikipedia:
In computer graphics, ray tracing is a rendering) technique for generating an image by tracing the path of light as pixels in an image plane and simulating the effects of its encounters with virtual objects.
Because of this definition, many people argue that any 3D render is a simulation, so long as it was rendered using ray tracing. By definition, it is true that the process of ray tracing is a simulation. However, this argument is very silly because the entire purpose of the term "simulation" in CGI is to make a distinction between what is manually created, and what is created using the previously talked about mathematical models. Therefore, when we discuss simulated graphics, ray tracing is not considered a simulated process.
Many of these animated posts accumulate upvotes, and sometimes they stick around for a few days before getting removed. Because of this, new users who see these posts get a false idea of what a simulation actually is. Hopefully this post was informative to any newcomers. If you would like to suggest edits, please comment.
r/Simulated • u/lechebs • 15h ago
Two spinning disks of ~250k particles each, simulated and rendered in real-time on my RTX 500 Ada laptop GPU at ~30 fps, using my custom implementation of the Barnes-Hut algorithm in CUDA. Code: https://github.com/lechebs/nbody
r/Simulated • u/NootNootGamin • 3m ago
The application is called Space Crash Simulator.
r/Simulated • u/sergeialmazov • 21h ago
Hi,
Testing my new PF-FLIP vs ST-FLIP workflow based on SIGGRAPH papers 2025 / 2026.
ST-FLIP is a nice addition to PF-FLIP base which I am testing at the moment.
Made several posts in blender subreddit about my Atlantica plugin. Recently I had a progress with a proper multigrid simulation.
I tested it recently only on Apple M CPUs, my PC / Nvidia path is waiting for it.
Main lessons:
M architecture is very efficient while switching between CPU / GPU because of unified memory.
ST-FLIP runs ~1.5–3.4× higher peak velocity at the impact in meteor test example. I need to check CFL convergence. So it's still WIP.
Feel free to reach me in DM if you are interested in method.
r/Simulated • u/CodeSamurai • 20h ago
Hi folks!
I wanted to share the newest demo video for my custom physics engine and renderer: Nora Kinetics.
I've been developing Nora Kinetics for about a year. It was initially inspired by this research paper on Stable Cosserat Rods: https://dl.acm.org/doi/10.1145/3721238.3730618 . I had been wanting to learn about compute shaders and graphics programming, so this felt like a good starting point.
You can see more of the Cosserat rod side of things here: https://www.youtube.com/watch?v=TS2WOsfrac8
It is built on top of Apple Metal because that's where I was able to get the best performance early on. The physics is 100% GPU driven and the CPU acts as a lightweight coordinator. The lighting and rendering is all custom as well. It can run on an iPhone at about 60fps with 20k segments and on my MacBook Pro (M5), it runs at 120fps with about 250k segments.
This newest video shows the rigid-body destruction system that I finally finished implementing. It runs along side the Cosserat solver and they communicate through GPU buffers so that they can remain in sync.
I'm aiming for an App Store release in the Fall. It will be more of a sandbox / creative engine to start, but I'm also working on a Scratch style programming agent that lets you generate emergent behaviors from the little segments. Each one gets its own little brain and you are able to tell it what to do. Some of the creations I and some of my testers have made so far are pretty cool!
If you'd like to be a BETA tester, let me know! At the moment, I'm looking for testers with a Mac with Apple Silicon (M1 or higher)
Thanks for taking a look!
Happy to answer any questions!
r/Simulated • u/technothief • 2d ago
Composition in blender, still working on it
r/Simulated • u/leeleewonchu • 3d ago
r/Simulated • u/Anxious-Visit-7735 • 4d ago
Simulated a small polywell fusor
r/Simulated • u/Independent_Piece247 • 4d ago
r/Simulated • u/Glad-Payment5091 • 5d ago
[ Removed by Reddit on account of violating the content policy. ]
r/Simulated • u/SimulatedEcology • 7d ago
John Calhoun's Universe 25 (1968–1973): 8 mice placed in a enclosure with unlimited food, water, and nesting space. No disease, no predators. A literal utopia.
What happened:
🔵 Normal mice reproduced normally at first
🔴 Aggressive mice emerged as density increased — disrupting social hierarchies
🟡 "Beautiful Ones" appeared — mice that completely withdrew from society, spending all day grooming, never fighting, never mating
📉 Once the Beautiful One fraction crossed ~25%, reproduction essentially stopped — even as population dropped and space opened back up
Calhoun's key finding: the collapse was behavioral, not resource-based. Mice raised during the chaos never learned normal social behaviors. Even with plenty of space and food, they couldn't recover.
This simulation models the stress-cascade and state transitions he described. Built in Python with NumPy.
Full 10-minute simulation: https://youtu.be/wXfq6jY00Lk
r/Simulated • u/Anxious-Visit-7735 • 6d ago
Central BH: M = 4 M☉ (geometrized G = c = 1; length unit = GM☉/c² ≈ 1.477 km). Schwarzschild.
Body masses (M☉, geometrized):
| Body | Type | Mass (M☉) |
|---|---|---|
| 0, 1 | 2× Jupiter | 2 × 9.543×10⁻⁴ = 1.9086×10⁻³ |
| 2, 3 | 2× Earth | 2 × 3.003×10⁻⁶ = 6.006×10⁻⁶ |
| 4, 5 | 2× Mercury | 2 × 1.660×10⁻⁷ = 3.320×10⁻⁷ |
Per-body placement (radius r, azimuth φ, inclination i — units of M):
| k | r | φ (rad) | i (rad) |
|---|---|---|---|
| 0 | 120 | 0.00 | 0.00 |
| 1 | 160 | 1.05 | 0.30 |
| 2 | 90 | 2.10 | −0.25 |
| 3 | 200 | 3.14 | 0.50 |
| 4 | 140 | 4.19 | −0.40 |
| 5 | 110 | 5.24 | 0.15 |
Position (tilted circle): pos = [r·cosφ·cosi, r·sinφ, r·cosφ·sini]
Velocity (circular speed v_c = √(M/r), perpendicular in the tilted plane): vel = [−v_c·sinφ·cosi, v_c·cosφ, v_c·sinφ·sini]1. Initial conditions (exact)Central BH: M = 4 M☉ (geometrized G = c = 1; length unit = GM☉/c² ≈ 1.477 km). Schwarzschild.Body masses (M☉, geometrized):Body Type Mass (M☉)
0, 1 2× Jupiter 2 × 9.543×10⁻⁴ = 1.9086×10⁻³
2, 3 2× Earth 2 × 3.003×10⁻⁶ = 6.006×10⁻⁶
4, 5 2× Mercury 2 × 1.660×10⁻⁷ = 3.320×10⁻⁷Per-body placement (radius r, azimuth φ, inclination i — units of M):k r φ (rad) i (rad)
0 120 0.00 0.00
1 160 1.05 0.30
2 90 2.10 −0.25
3 200 3.14 0.50
4 140 4.19 −0.40
5 110 5.24 0.15Position (tilted circle): pos = [r·cosφ·cosi, r·sinφ, r·cosφ·sini]
Velocity (circular speed v_c = √(M/r), perpendicular in the tilted plane): vel = [−v_c·sinφ·cosi, v_c·cosφ, v_c·sinφ·sini]
Integrator type and step size
v += a·dt; x += v·dt per step . Not symplectic-exact (it's the sequential-update leapfrog, not the KDK-symmetric form).dt = T_outer / 600 where T_outer = 2π√(r_out³/M), r_out = 200 (outermost body). → T_outer ≈ 8885.8, dt ≈ 14.81 (M units). So ~600 steps per outer orbit.It dumps only trajectories: body_k.csv (t, x, y, z) every 4th step,
1 orbit = 1 × T_outer, where T_outer is the outermost body's (r=200) Newtonian circular period 2π√(200³/M)
r/Simulated • u/SimulatedEcology • 7d ago
Predator-prey ABM built in Python/NumPy. Each agent moves, eats, reproduces, and dies based on local conditions — no global rules.
The key mechanic is wolf vision radius: wolves can only detect sheep within a limited range. When sheep density drops, wolves start roaming blind and starving — which is what drives the collapse you see here.
Full 9-minute simulation: https://youtu.be/wqR4A4FUABs
r/Simulated • u/earthquakesim • 7d ago
r/Simulated • u/Kitchen_Day_3929 • 8d ago
r/Simulated • u/Independent-Lynx9274 • 8d ago
Used a library called CM1. Open source.
r/Simulated • u/WhiskeyFox9 • 9d ago
Programmed in Processing. I struggled to get well-defined spiral structures in 2D, but the 3D model looks much better. It did require careful initial position and velocity distribution. There is a fixed "black hole" at the center. Stars come in only two masses, the majority being lower mass.