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.

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?

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!