r/Simulated • • Sep 22 '18

Meta What is a simulation? A detailed comparison between Animation, and Simulation.

985 Upvotes

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.

What is a simulation?

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.

How are simulations different from animations?

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.

The "Ray tracing)" argument.

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.

Examples of animated (non-simulated) posts:

  1. "Satisfying simulations" - 3.4k upvotes
  2. "Bender's old job" - 2.2k upvotes
  3. "Up or Down?" - 1.4k upvotes
  4. "Adobe Dimention Rendering" - 1.4k upvotes
  5. "Depression - Robert Ek"

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 • • 13h ago

RealFlow I've made a very realistic marbling simulation

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175 Upvotes

Hey everyone!

so you can basically almost do everything you can in real marbling, i've tried to make it to produce even more high resolution outcome but computational power increase exponantially because of water grids so it's impossible after some points. But you can get high resolution as high as 300 DPI in A3, and it's fun to learn marbling even at lower settings.

It runs on a browser and it's free so pls go check it out!

https://marblingstudio.app/


r/Simulated • • 13h ago

Proprietary Software Realtime Headbanging Simulation

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116 Upvotes

What I see when I'm VJ-ing. Part of the TouchDesigner POPtober challenge. Today's POP: sprinkle POP


r/Simulated • • 22h ago

Interactive Starlight carving a nebula: my open-source GPU simulator (NVIDIA Warp)

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392 Upvotes

Gas dynamics + ray-traced ionization fronts on the GPU: stars heat the gas to 10,000 K and the pressure carves the shapes. Code:
github.com/felipehez/NebulaViewer
Music: The Field of Dreams by pauliuw (CC0).


r/Simulated • • 1d ago

Research Simulation [OC] Forest fire automata

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247 Upvotes

​

This is a stochastic cellular automata based on the Drossel–Schwabl forest fire model implemented on a hexagonal grid using numpy + matplotlib. Inspired by some of my old university notes from a course on computational biology.

I especially like the patterns formed by the fire spreading and the forests regrowing one tree at a time, a beautiful example of self organizing complexity.

Fire starts on any cell with p_fire = 0.0001 by a "lighting strike", while trees grow on empty cells with p_tree = 0.01. Fire spreads to all neighboring trees.

I initially worked with a rectangular grid however moved to a hexagon version to have more organic symmetry in spreading directions.


r/Simulated • • 1h ago

Proprietary Software Another candle

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• Upvotes

r/Simulated • • 1d ago

Research Simulation HézFX - Muscle Stimulation Tool

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99 Upvotes

After many years of active research and development, I finally have the tool available :)

https://hezfx.shirzadbahrami.com/


r/Simulated • • 21h ago

LiquiGen large scale impact study

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34 Upvotes

r/Simulated • • 1d ago

Houdini droplet slides down the flower💧

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150 Upvotes

r/Simulated • • 1d ago

Proprietary Software [OC] The Milky Way and Andromeda collide and merge into one galaxy: 39.5 million particles, about a billion years in 39 seconds

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28 Upvotes

Particle sim of the Milky Way and Andromeda (about 1.6x our galaxy's mass in this run) falling together, plunging through each other and throwing out tails and shells of stars, then falling back in and settling into one round blob, basically an elliptical galaxy in the making. 39.5 million particles, rendered offline, silent, nothing audio reactive this time.

The slow approach is sped up 1.5 to 4x so it doesn't drag, the passes and the merger play at the original pace. The full realtime version is 60 s.

For the real thing: they're about 2.5 million light years apart right now, closing at ~110 km/s, first pass is expected in roughly 4 to 5 billion years, and recent work puts a full merger at about even odds within 10 billion. The sim starts them close to skip the boring part, and this orbit is one representative outcome, not a prediction.


r/Simulated • • 20h ago

Proprietary Software Physics based fire

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3 Upvotes

r/Simulated • • 2d ago

Research Simulation The biomechanics of running into a wall

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615 Upvotes

r/Simulated • • 15h ago

Blender I Simulated a Subway Flood in Blender Using Mantaflow and Custom Scripts

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0 Upvotes

r/Simulated • • 1d ago

Proprietary Software [OC] Two galaxies colliding: about a million star particles, each pulled by both galaxy cores and their dark-matter halos, integrated live on the GPU

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35 Upvotes

Toomre & Toomre (1972) style encounter: 1,048,576 stars as test particles, each feeling two softened galaxy cores, and each core sits in a logarithmic dark-matter halo with dynamical friction, so after the first pass the orbit decays and the pair merges. Leapfrog (kick-drift-kick) on the GPU in Metal, a couple of substeps per frame. There's also sticky gas on a 64³ grid, which is what lights the pink knots when the cores collide.

It runs live in my own engine (in the app it's at 90 Hz on Vision Pro). This clip was rendered frame by frame from the same engine's Mac test harness so I could export it cleanly. Happy to answer questions about the setup.


r/Simulated • • 1d ago

Research Simulation Real-time 2D fluid sim in Python

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1 Upvotes

I wanted to understand fluid simulation, so I built a 2D one in Python. About 9,000 particles, you can grab the fluid with the mouse, lift it and drop it.

My first version ran at about 10 FPS. The big problems were:

  • Every particle was checked against every other one, roughly 80 million pair checks per step. I put the particles in a uniform grid with cells the size of the smoothing radius, so a particle only looks at the 3x3 cells around it.
  • The loops were plain Python. Moving them to Numba helped a lot.
  • I switched from computing pressure forces directly to Position Based Fluids. It predicts positions, then nudges crowded particles apart over a few iterations, and takes velocity from how far they moved. It stays stable at much larger time steps than the force-based version I started with.

This was inspired by Sebastian Lague Coding Adventure. I made this in python and optimized it further.

Here's the Repo and a small article for understanding

This was my very first optimization project and also in graphics, it's still a little rusty, so if you see something wrong in the kernels or have ideas for making it faster, I’d like to hear it.


r/Simulated • • 1d ago

Proprietary Software Cymatics

2 Upvotes

The nodal patterns emerge deterministically from mechanical wave equations and particle interaction dynamics, entirely procedural without any cymatics specific code implemented, and dynamic sound emerges from the conditions present in the engine. Everything is derived from a floor of shared physical constants through a single shared evaluator, there is no UV, collision, or geometry present anywhere in the engine.


r/Simulated • • 1d ago

Research Simulation Tips for Building a FEM or XPBD for C4D

0 Upvotes

I’m prototyping a muscle tool for Cinema 4D and could use some advice. The goal is believable, reasonably fast deformation, not medical accuracy.

The current custom solver uses:

\- Linear tetrahedral FEM-style discretization: 525 nodes / 1,920 tets for one simplified biceps belly.

\- Custom strain, shear, volume-preservation and fiber-length energies. Activation changes the preferred fiber length. It’s not a calibrated tissue or Hill-type muscle model.

\- Implicit time stepping solved with exact-Hessian trust-region Newton and truncated conjugate gradients.

\- Python/Numba, currently single-threaded CPU. A separate higher-resolution surface follows the simulated tets.

The problem: six seconds of motion takes roughly 30.7 minutes, using 12 substeps per frame at 30 fps. Profiling found 68% of the bake goes into Python Decimal energy-change checks, triggered on every solver proposal. Even removing that cost entirely would leave about 10 minutes.

Attachments are prescribed, the tendon isn’t physically solved, and there’s no collision handling yet. Numerical checks pass, but the visual result still isn’t convincing.

Would you simplify this into a coarse XPBD approach for authoring, or improve the existing solver first? What would you prioritize for speed and believable muscle behavior?


r/Simulated • • 1d ago

Blender From Curiosity to Creation: I Built a One-Click Marble Music Animation Add-On for Blender 🎵🔵

0 Upvotes

8 months ago, I posted a question on Reddit asking how to create animations like marble music videos. I was curious about how these animations worked and wanted to learn how to make them myself.

Here was my original post:
https://www.reddit.com/r/blender/comments/1rjegy7/how_to_create_animations_like_this_marble_music/

Unfortunately, I couldn't find anyone to guide me at the time. So, I started searching the web, watching YouTube tutorials, experimenting, and learning Blender on my own.

Fast forward to today, and I can confidently say that I've learned how to create almost any kind of marble music animation. You can see my work on my YouTube channel:
🎵 https://www.youtube.com/@MarbleMelo

But something unexpected happened along the way.

While creating these animations, I discovered a way to automate the entire process. What started as a personal learning journey eventually turned into a Blender add-on called Melo Marble.

With Melo Marble, you can generate a complete marble music animation with just ONE CLICK. 🚀

The jumping marbles, swinging movements, zigzag paths, trails, tails, and other animation elements can all be generated automatically, saving you the time and effort of creating everything manually.

🔗 Check out the add-on: https://melomarble.hutzon.com/

I've already shared a guide on my YouTube channel to help you get started.

For me, this is more than just an add-on. It's the result of a real learning experience—starting with a question nobody answered, figuring things out independently, and turning what I learned into a tool that others can use.

I wanted to understand how marble music animations were made. Now, I've built a tool that helps others create them much more easily.

Sometimes, the best tools come from solving a problem you've experienced yourself. ❤️

If you're interested in Blender, animation, or marble music, give Melo Marble a try and let me know what you think!


r/Simulated • • 1d ago

Interactive [OC] tribes spreading and splitting in my civilization sim, every tribe ends up with its own language

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0 Upvotes

r/Simulated • • 4d ago

Proprietary Software Realtime fire sim

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168 Upvotes

Modified my fluid simulation to work with gasses too.

To everyone who messaged after my last post, I've booked next week off work to get this tested and out on the play store. Hold tight.


r/Simulated • • 4d ago

Interactive Took me a decade to fully simulate universal quantum logic, results here

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51 Upvotes

Hi

This is about Quantum Odyssey, my love letter to everything Quantum Computing and the fundamental logic blocks everything in our universe seems to run on. I want to update you all on the fact that the latest patch brings the game into an almost complete status. All that's missing is translations. Thank you Reddit community for receiving the game so well, without you I wouldn't have the funds needed to complete my life's work.

If you are remotely interested in deep diving how differently quantum computers work compared to our transistor-based and also the algebra behind in a fully interactive way that teach computer science from scratch, oh boy this is for you. I am the Dev behind Quantum Odyssey (AMA! I love taking qs) - worked on it for about 9 years (3+ during PhD, the visual method I developed ended up being my thesis, it is a complete Hilbert space visualizer), the goal was to make a super immersive space for anyone to learn quantum computing through zachlike (open-ended) logic puzzles and compete on leaderboards and lots of community made content on finding the most optimal quantum algorithms. The game has a unique set of visuals capable to represent any sort of quantum dynamics for any number of qubits and this is pretty much what makes it now possible for anybody 15yo+ to actually learn quantum logic without having to worry at all about the mathematics behind.

This is a game super different than what you'd normally expect in a programming/ logic puzzle game, so try it with an open mind.

Stuff you'll play with

  • Boolean Logic – bits, operators (NAND, OR, XOR, AND…), and classical arithmetic (adders). Learn how these can combine to build anything classical. You will learn to port these to a quantum computer.
  • Quantum Logic – qubits, the math behind them (linear algebra, SU(2), complex numbers), all Turing-complete gates (beyond Clifford set), and make tensors to evolve systems. Freely combine or create your own gates to build anything you can imagine using polar or complex numbers.
  • Quantum Phenomena – storing and retrieving information in the X, Y, Z bases; superposition (pure and mixed states), interference, entanglement, the no-cloning rule, reversibility, and how the measurement basis changes what you see.
  • Core Quantum Tricks – phase kickback, amplitude amplification, storing information in phase and retrieving it through interference, build custom gates and tensors, and define any entanglement scenario. (Control logic is handled separately from other gates.)
  • Famous Quantum Algorithms – explore Deutsch–Jozsa, Grover’s search, quantum Fourier transforms, Bernstein–Vazirani, and more.

Nice to watch:

Khan academy style tutorials in qm/qc: https://www.youtube.com/@MackAttackx

Physics teacher stream with 400hs in https://www.twitch.tv/beardhero


r/Simulated • • 4d ago

Research Simulation Jellyfish, fish and bionic aircraft based on my experimnts

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12 Upvotes

r/Simulated • • 3d ago

Research Simulation Blackhole Gargantua from intersteller simulated using openGL and C++

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3 Upvotes

i made a simulation of the blackhole gargantua that is also seen in intersteller It's written in C++ and openGL

  • schwarzschild equation
  • doppler effect
  • adjustable quality

i managed to optimize it to a point i ran on my i3 intel iGPU, although i added very low to high quality toggles, it's my first time writing in glsl so yeah, i was a lot inspired by the yt video of Kavan about making a blackhole in cpp, so i just wanted to make it more realistic, my astrophysics lectures kinda came in clutch

github repository : https://github.com/dummy3ye/blackholegl (star the repo if you like it)

[!Important]

This main project is written by human, Not LLM's. only help taken from llm is in the release pipeline because it's too problematic to maintain multi-platform releases for one person.


r/Simulated • • 5d ago

Proprietary Software Being orange simulation

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467 Upvotes

Made in TouchDesigner (sorry the flair doesn't exist) as part of the POPtober challenge. Today: field POP


r/Simulated • • 5d ago

EmberGen I feel fine

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188 Upvotes

Planetary scale explosion created using various assets from Kris Brad
https://www.instagram.com/kris_bradd/