Running on a Snapdragon 8 Elite Gen 5.

Several SPH/N-body simulation with black holes, simulated using SpaceSim, a software I'm developing.

The Mediterranean runs at a loss: it evaporates about 0.5-1 m of water level per year more than rain and rivers put back, and the Atlantic covers the deficit through Gibraltar around the clock. My simulator derives a 0.7 m/yr deficit on its own from its climate model - right in the textbook range - so I felt entitled to do something irresponsible with it.

I sealed the strait (14 km wide at its narrowest) and let it run. No scripted animation - every cell tracks its own evaporation, precipitation and river inflow each year, and global water volume has to conserve to within 2 parts in 10,000.

Timeline:

- 25 years: level down 17 m. Venice's gondoliers are the first out of work.

- ~500 years: the Adriatic is gone (average depth only 250 m).

- ~700 years: the Sicily-Tunisia ridge surfaces and the Med splits into two shrinking lakes. When this actually happened 5.97 million years ago, hippos walked to Cyprus - their stranded descendants shrank into dwarf hippos. The fossils exist.

- ~2,100 years: the basin is effectively dead. 2.5 million km² of new land, nearly the size of Argentina, crusted with precipitating salt.

- ~4,300 years: the deepest pools bottom out. Except one - a bitter lake in the east kept on life support by the Nile. I never coded that; evaporation, rivers and terrain balanced it into existence on their own.

The Black Sea survives: once its level drops below the Bosporus sill it detaches and holds steady on the Danube and Dnieper. The Caspian was my control group - untouched, it drifts 17 m in 300 years and then stabilizes.

This genuinely happened. It's called the Messinian Salinity Crisis: 5.97 million years ago Gibraltar really did close. In 1970 the drillship Glomar Challenger pulled gypsum and rock salt out of the Mediterranean seafloor under 3,000 m of water. My simulator has never heard of the Messinian - it just agrees with the drill cores.

It's all from a game I'm building where you do this with a brush. Link in the comments to keep things tidy.

I couldn't find a tag that fit so I just picked Proprietary, but I made it in Unity.

Edit: because people have a lot of really good questions, I'm adding the link for the longer video here: https://www.youtube.com/watch?v=TIdHDe0JUpw&lc=UgyLw_Z8QZ-GH2CSxRp4AaABAg . This should answer most questions, and I'm super happy to answer any that it doesn't!

Part of the TouchDesigner POPtober challenge. Day 11. Attribute POP. Sorry, can't set TouchDesigner as flair

CPU only, 900 objects.

As a follow up from a comment on https://www.reddit.com/r/Simulated/comments/1w4d85s/comment/p78ugx4/?screen_view_count=2&ext-referrer=DIRECT, I had fun with this one.

The fog is a fluid sim, and the logogram is a phenomenon on top of. Ink is emitted along the glyph's stroke by a travelling pen that the fluid carries, and a target-driving force pulls the density toward the finished glyph without ever snapping it there (Fattal and Lischinski's 2004). It is reacting to whatever music is playing while you watch.

Built in Swift and Metal as part of TideGlass, a small Mac app I make where worlds like this run on a second monitor while you work. Happy to answer anything about the sim.

This runs live on an Apple silicon GPU.

Every bird reacts only to the ones near it. Nothing choreographs the shape and nothing is keyframed, so what you are watching falls out of 137,500 of them following local rules at once.

It is a GPU flock on an atomic spatial hash, which keeps neighbour lookups linear instead of quadratic at that count. Each bird steers on a bounded turn rate and banks into its turns, and the banking is what makes the flock flicker as they roll.

Based this on starling literature rather than plain boids, mostly Cavagna's work on scale-free correlations in real flocks and Couzin on spatial sorting. Cool thins is that the same system with one flag flipped runs a bait ball instead: change the attractor from polarised streaming to milling and the sheet becomes a rotating sphere.

Built in Swift and Metal as part of TideGlass, a small Mac app I make where worlds like this run on a second monitor while you work. Happy to answer anything about the sim.

XPBD softbody simulation in POPs using Gauss-Seidel @ 60fps and 70 shader passes (can't do substepping in same shader pass)

When TouchDesigner introduced POPs one of the first things I tried making was an xpbd soft-body sim, and it looked like this and this. Since then, I've rewritten it multiple times and watched ten minute-physics' tutorials over and over. Many simulation explosions later, it turned out that my very first solver was (mostly) correct, but I was colouring the graph and building the tet constraints in the wrong way..

Edit:

Resources:

Ten Minute Physics

Eric Arnebäck's blog

Vivace

XPBD paper + earlier PBD paper from Macklin

I'm working on this destruction focused imsim that's like Falling Down meets wall-e. I put a lot of effort into making the bat respond physically accurately to surfaces and collisions. the game will also have walking and balance simulation for characters with legs.

https://x.com/Fleech_dev/status/1923027152716411005

Built a tool and started a youtube channel with my kids visualizing music and simulating physics: https://www.youtube.com/@Orbodrome

Hi, I'm back here again to answer the most popular questions from the last post. This time, I included a voiceover to explain a bit better what's actually going on here. I'm not sure if this type of post is allowed, so if there's somewhere else I should be posting this please let me know!

As before, if you want a more comprehensive crash course in 4D, please check out my full video on the subject: https://www.youtube.com/watch?v=TIdHDe0JUpw

This clip is from the upcoming 9th youtube video I made with my kids. If you like this clip, this video is along the same lines: https://www.youtube.com/watch?v=J7pERS6A1z0

This video is from 2020, from our sandbox voxel simulator called BFS. It was running back then in Unity 3D. It took us another 6 years to make that scene multiplayer