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Inside the heart

An 80-second explainer for a beginner: what the four chambers of the heart are, and how blood moves through them.

Made by Claude Code with manimvox

This video was made by an AI agent, Claude Code, using manimvox's skills and library. A person directed it with a few prompts and reviewed the result. The agent did the research, the facts, the script, the code, the drafts and the render.

The prompts

These are the prompts that shaped the video, with spelling tidied:

  1. "Give me a short, simple video explaining the various parts of the human heart, with a smooth rotating heart."
  2. "The graphics are simple. This should be high-quality educational content made at low cost with Manim, so make the diagram cleaner and explain it clearly and briefly, like a professor. Cut it open and properly show the blood flow."
  3. "Use the internet to download 3D models."

What the agent did

  1. Found a real heart. It searched for an openly licensed model with the inside of the heart, checked the licences, and chose case 18 of a CT-derived four-chamber heart cohort (Rodero et al. 2021, CC BY 4.0). Its walls, great arteries and valve planes are labelled in the data.
  2. Wrote the facts first. Every line of narration is in FACTS.md, sourced from NHLBI and the Cleveland Clinic. Claims it could not source, such as "the size of a fist", were left out.
  3. Cut the heart open on screen. It found the classic four-chamber plane from the data itself (through the apex and the centres of the mitral and tricuspid valves), and used from_pyvista to render the heart turning and then the cut sweeping in from the front.
  4. Drew the labels and the blood. screen_xy gave each landmark's pixel in the rendered frame, and Clip.at turned it into a scene point. Atlas-style labels and streams of blood (blue through the right side to the lungs, red through the left side to the body) are drawn there in Manim.
  5. Checked its work. It drafted, read the contact sheets and the layout check, fixed overlapping labels and a confusing route, and rendered the final video only when every check passed.

While making it, the agent also extended manimvox: from_pyvista, screen_xy, Clip.at and Clip.loop were added for this video, and are now part of the library.

Source

The whole project is in examples/gallery/heart: the episode, its script, the facts, and the script that prepares the CT data. To render it yourself:

uv tool install "manimvox[kokoro,pyvista]"     # or: pip install "manimvox[kokoro,pyvista]"
python prep_ct.py path/to/18.vtk research/ct
manimvox render ep01

Credits

  • Heart mesh: Rodero C., Strocchi M., Marciniak M. et al., Virtual cohort of adult healthy four-chamber heart meshes from CT images, Zenodo, 2021, doi:10.5281/zenodo.4590294, CC BY 4.0.
  • Facts: NHLBI, How the Heart Works; Cleveland Clinic, Heart Chambers.
  • Voice: Kokoro (af_heart).
  • Made by: Claude Code with manimvox.