Claude Built a Black Hole in a Browser. Here's how.

Claude built this black hole formation animation in AtomCut through MCP: 30 seconds, 900 frames, a star collapsing into darkness and an accretion disk curling around it. The result is an editable motion project, with gravity wells, particle emitters, effects, captions, and a sound mix on the timeline.

AtomCut is a motion design and video editor that runs in the browser and on desktop. This project shows what happens when an AI model can operate the editor's physics and animation tools directly.

The finished 30-second animation, embedded from the creator’s YouTube Short.

Watch the video on YouTube · Watch or download the original 1080p MP4.

How was the black hole animation made?

The project has a main 1080 × 1920 composition and a separate 1400 × 1400 composition called Disk. That second composition contains just two layers: Disk gas and Disk well.

Two layers is a surprisingly small place to put a cosmic disaster.

The main timeline handles the story: the star, outward wind, inward gas, collapse, a shockwave, the disk reveal, captions, and the final grade. The nested disk handles the orbiting particles independently. You can change its physics without digging through the captions above it.

Six moments from the same finished MP4. No reconstructed scenes or generated stand-ins.

At the start, the star fills the frame. The view pulls back; particles stream outward, then inward. Around 12–16 seconds, the star contracts and flares. Darkness takes over, a ripple expands, and the tilted disk arrives after 18 seconds.

Those beats are authored on a timeline. The particle paths within them come from the simulation.

The original supplied screenshot, unchanged. The layer names are the actual project structure.

What physics makes the accretion disk move?

Inside Disk, scene gravity is zero and the floor is off. Otherwise, your black hole demonstration has an unexpected downstairs.

Disk well carries a gravity force with these saved values:

{
  "type": "gravity",
  "mass": 8000,
  "core": 8,
  "horizon": 30,
  "spin": 0.5
}

These are editor units, not solar masses or kilometres. The force uses softened inverse-square attraction: the core keeps the acceleration finite near the centre. Particles crossing the horizon are removed. spin adds an approximation of frame dragging.

A useful starting point for an orbit is:

GM = mass × 10,000
circular speed ≈ sqrt(GM / radius)

The approximation applies away from the softened core. With mass 8,000 and radius 200, that is about 632 editor units per second. An orbital emitter launches particles sideways relative to the well, so the pull curves their paths around the centre.

Gravity alone can sustain an orbit. To make material spiral inward, you need a way to change that motion. This disk combines a small particle drag value, 0.004, with the well's spin control.

The second original screenshot: three Stream cards on Disk gas, with Disk well directly underneath.

Why does the disk look like several rings?

The saved Disk gas layer has three simultaneous particle streams, emitting a combined 3,100 particles per second. That is an emission rate, not the number visible at once.

All three use orbital launch, an orbit multiplier of 1, and the same drag. The first two draw fine sparks. The third draws larger, soft dots behind them to fill out the disk.

Those temperature values control a speed-based blackbody color mapping. They are visual settings, not temperatures recovered from a gas dynamics calculation.

The actual project settings, arranged as a reading guide. This is a parameter diagram, not a replacement rendering of AtomCut.

The view controls do another job:

• Tilt: 83° projects the disk almost edge-on.
• Lensing: 1 adds the bent images of the disk around the dark centre.
• Beaming: 0.6 changes the apparent brightness and color according to motion toward or away from the view.

These controls affect how particles are drawn. They do not change their simulated paths. That separation is useful: you can tune the silhouette and brightness while keeping the underlying motion.

Is this an astrophysics simulation?

It is an art-directed physics animation. The orbiting particles respond to numerical forces; the star's contraction, shake, temperature, and brightness are keyframed. Nebula and starfield effects provide the background. A separate lens effect, a drawn spacetime funnel, glow, a shockwave, and grading shape the presentation.

It does not solve Einstein's field equations, stellar evolution, radiation transport, or relativistic fluid dynamics. Lensing and frame dragging are approximations designed for motion graphics. The film compresses a simplified stellar-collapse story into half a minute; the visible disk is a storytelling choice, not a claim that every collapsing star produces this view.

The end card says “Gravity, light and gas — all simulated.” Read that as the film's visual shorthand. The more precise description is force-driven particles combined with procedural effects and authored animation.

What does Claude actually control through MCP?

MCP, the Model Context Protocol, connects an agent to AtomCut's commands. Claude can inspect the document, create layers, configure forces and emitters, add keyframes, render frames for inspection, and revise the project.

That changes the workflow. A request such as “make the disk less tilted” can become an edit to an existing particle setting. The project keeps its layers and controls, so you can also make that change yourself in the Physics panel.

For this scene, the relevant tools include physics_scene, physics_force, physics_emit, keyframes_set, and the render inspection tools. The numbers above come from the saved project inspected for this article; they are not a fabricated transcript of Claude's original tool calls.

AtomCut supports Claude, GPT, Gemini, local models, and other supported providers or OpenAI-compatible endpoints in its built-in agent. External agents need an MCP-capable client and AtomCut's agent link. Model choice still matters: for this kind of multi-step visual work, the maker's current preference is Claude, especially Opus. That is a working preference, not a controlled benchmark against every model.

How can you try the workflow?

Open the studio, then Agents → Use your agent app → Link. For Claude Code, add the MCP server:

claude mcp add atomcut -- npx -y @atomcut/mcp@latest

A focused first brief is easier to inspect than an entire cinematic sequence:

Create a zero-gravity composition with a central gravity well and an orbiting particle ring. Keep the well and emitter on named layers. Render frames at several times, inspect the motion, and leave the controls editable.

That is a starting brief, not the original prompt or a promise of a one-shot match. Get the orbit working first. Then add the collapse, view treatment, typography, and sound.

The physics documentation explains bodies, forces, particles, and simulation settings. The AI documentation covers model connections and the agent workflow. The editor is free; agent features require AtomCut Pro and your own model connection.

Build your first orbit in AtomCut: app.atomcut.net