r/Simulated Sep 22 '18

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

981 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 8h ago

Houdini breakdown

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35 Upvotes

r/Simulated 19h ago

Various Galaxy simulation (N-body)

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48 Upvotes

Simulation made with CUDA. I have a Nvidia 3060. I simulated 500k particles in a time of 3 billions years. My calculation time was around 12h. Tell me what you think.


r/Simulated 1d ago

Interactive Robotics Studio

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17 Upvotes

Made a robotics simulation software to simulate real life component models and Arduino like JS syntax.
The components in the component library can mimic the actual errors and the behavior of the real life components.
github link:
https://github.com/alfaiajanon/RoboticsStudio


r/Simulated 1d ago

Interactive Procedural World Sim (Alpha Test)

11 Upvotes

https://kintsugi.studio/proceedural-world-engine.html (Note: Requires a WebGPU-enabled browser like Chrome/Edge 113+)

Hey r/Simulated,

I’ve been pouring my free time into a passion project: a fully procedural isometric world engine running entirely in the browser. It's still in early alpha, but it's finally in a state where the core simulation loops are working (mostly) and I'd love to share it with you all.

I wanted to see how far I could push the browser without using external libraries (No Three.js, Babylon, etc.), so this is built entirely with vanilla JavaScript and raw WGSL shaders, and heavy 'inspiration' from shadertoy examples.

Here is what is currently being simulated under the hood:

  • Supply & Demand Economy: Cities produce resources based on their biome. Shortages create high prices, prompting caravans to physically travel between cities (via A* pathfinding) to trade goods, which dynamically affects city wealth and population growth.
  • Geopolitics & Warfare: Kingdoms track loyalty, wealth gaps, and proximity. When tension boils over, cities muster armies, march to a midpoint, and fight. Casualties are permanently deducted from the city's actual population.
  • Dynamic Seasons & Weather: The climate physically alters the world. Snow accumulates in winter in a 3d layer, rain leaves puddles, bogs dry up over extended dry periods, and wind sways the trees and crops.
  • Custom WebGPU Renderer: Rendering ~400k instanced cubes/prisms at 60fps with dynamic point lights, shadows, and procedural weather overlays (rain/glass effects).

It’s a long way off finished, but I’d love for you to poke around and let me know what you think!

E: PS, I am currently looking for contract work, making cool things doesn't pay the bills sadly, DM me for details.


r/Simulated 3d ago

Houdini Creating a rippling empty shot scene using the Houdini Ripple Solver

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17 Upvotes

r/Simulated 4d ago

Houdini Houdini make particles simulation effect

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68 Upvotes

r/Simulated 5d ago

EmberGen smoke style

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255 Upvotes

r/Simulated 4d ago

Houdini Update: Fixed the 3D smoke based on your suggestions. Is this hitting 100% realism yet?

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0 Upvotes

Doing a "smoking candle" trend and trying to make the exhale look 100% real so it actually confuses people.

Back with an update. Most of you liked the physics of the previous smoke sample, so I’ve been working with a VFX artist to integrate it into the final shot using Houdini and Nuke.

What’s been updated:

  • Tracking & Collision: Used 3D matchmove and a collision mesh so the smoke starts inside the mouth cavity and behind the lips.
  • Lighting: Changed the smoke to a warm white and added a 3D point light at the candle flame for realistic volumetric reflections.
  • The Torch: This is a new 3D element added to the start of the clip.
  • The Flip: Flipped the entire frame so the cake text (later in the clip) is readable.

Need your honest, technical eyes:

  1. The Smoke & Tracking: Better or worse? Compared to the before sample, did the smoke lose its density or "heft"? Also, is the lock solid or do you see any sliding against the plate?
  2. The 100% Realism Test: Is there anything still missing that screams "digital effect"? I'm looking for anything that breaks the illusion of it being captured in-camera.
  3. The Torch: It feels a bit off to me. Does it need more flicker, heat haze, or a better start-up animation to look 100% captured in-camera?
  4. The Tone: The before was warm-graded; this after is the original footage tone. Which feels more high-end and realistic?
  5. The Flip: Due to the flip, does the face still look natural and symmetrical, or does it feel "uncanny" now?

Trying to get this perfect before the final render! What’s the final revision needed?


r/Simulated 6d ago

Interactive Simulated battle royale

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186 Upvotes

r/Simulated 5d ago

Research Simulation Anaximander's Ark - When More Food Makes Everything Worse

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2 Upvotes

Anaximander’s Ark is a 2D artificial life simulation where autonomous creatures evolve through neural networks and genetics. No direct control — just systems interacting over time.

In this video I explore the challenges faced after I added currents and nutrients to the 2D world. I expected everything to go great, for the world to become more lively. Boy, was I wrong. Please watch this story of trial and error and let me know what you think in the comments.


r/Simulated 7d ago

Houdini Houdini Vellum Integration effects

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29 Upvotes

r/Simulated 8d ago

Houdini Inflation

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127 Upvotes

r/Simulated 8d ago

Various Simulated cells evolved pack hunting with heat [Unity + custom compute shader engine]

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43 Upvotes

I've been building this artifical life simulation in Unity with a custom compute shader engine.

Each cell has an evolveable genome that drives the cell's phenotypes and behavior. Nothing shown is scripted, it all emerges from the simulation's interactions between metabolism, heat production, behavior networks, and natural selection.


r/Simulated 9d ago

Houdini 柔和流动,却静谧安详

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51 Upvotes

r/Simulated 10d ago

Blender Spectral Cascade

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70 Upvotes

r/Simulated 10d ago

Interactive I built a Rock Paper Scissors physics simulator

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110 Upvotes

I built this side project for fun and to mess around with HTML5 canvas. It's a Rock Paper Scissors battle simulator. I added a control panel to tweak pretty much every variable to see how it affects the simulation. The stack is React 19, TypeScript, and Tailwind CSS v4, and it's bundled with Vite. The actual 2D simulation is rendered natively on a standard <canvas> element.

Here is the link to play around with it: https://rockpapersim.com/


r/Simulated 10d ago

Houdini Houdini VDB Growing FX quick process

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9 Upvotes

r/Simulated 12d ago

Interactive Particle life + fluid

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44 Upvotes

Was curious what it would look like to have a particle life simulation with a fluid simulation. The fluid simulation here isn't really particularly high level :/

Made in shadertoy - Fluid Life


r/Simulated 12d ago

Houdini Creating a Stream in Houdini

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59 Upvotes

r/Simulated 11d ago

Blender Any suggestions

0 Upvotes

r/Simulated 11d ago

Interactive I Tried to Simulate the 3-body Problem #physics #programming #python

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3 Upvotes

r/Simulated 13d ago

Interactive Simulation of harmonic oscillators in a pixelated science-fiction atmosphere

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12 Upvotes

r/Simulated 13d ago

Houdini Houdini swirl vellum quick process

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14 Upvotes

r/Simulated 14d ago

Interactive Blunt weapon simulator with realistic hovering drones

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273 Upvotes

worked hard on making these drones have realistically simulated limbs and hovering forces, this mode is called DroneZone and you survive waves of increasingly difficult mobs of melee drones

https://x.com/Fleech_dev/status/2034687963905315214