vexy-stax

Render a deck of layered PNG slides as 3D glass plates — in two views and the transitions between them — from a single shared JSON scene format. This is the offline Python package; a browser sibling (vexy-stax-js) consumes the same scene format. See the repo-level SPEC.md for the binding contract.

This package implements the scene model, geometry math, CLI, and three fully functional render backends: Blender, pygfx, and Playwright.

Install

uv venv --python 3.12 && uv sync

Concepts

• A scene is an ordered list of slides (back-to-front; index 0 is farthest from the camera) plus camera, floor, and transition settings.
• Two views: expanded (angled, plates spaced by gap, captions on) and compact (head-on, plates collapsed to MIN_GAP ≈ 3 pt).
• A transition morphs between the views (expand, collapse, expand_collapse, collapse_expand), interpolating camera, spacing, and per-slide opacity with a shared easing curve.

CLI

vexy-stax dir2scene assets/ --out scene.json             # generate scene JSON from directory
vexy-stax render    scene.json --view expanded --engine pygfx   --out beauty.png
vexy-stax render    scene.json --view compact  --engine blender --out stack.png
vexy-stax video     scene.json --engine blender --out morph.mp4
vexy-stax overlay   scene.json --out flat.png          # pure-Pillow flat composite
vexy-stax engines                                      # list available engines

Defaults: still ⇒ pygfx, video ⇒ blender. A missing/unimplemented engine fails with an actionable message, not a crash.

Library

from vexy_stax.scene import load_scene
from vexy_stax import geometry as g

scene = load_scene("scene.json")          # validates + resolves slide paths
plan = g.frame_plan(scene)                 # per-frame camera/spacing/opacity
pose = g.expanded_camera(scene)            # CameraPose dataclass

vexy_stax.scene is a strict pydantic v2 model (extra="forbid" everywhere — unknown fields fail loud at the boundary). vexy_stax.geometry holds the pure, engine-agnostic view math (SPEC.md §3), mirrored by the JS geometry.js against shared fixture vectors.

Layout

src/vexy_stax/
├── scene.py        # pydantic v2 scene model + loader
├── geometry.py     # §3 camera/spacing/opacity math (pure, engine-agnostic)
├── engines/        # base.py protocol + registry; blender, pygfx, and playwright renderers
├── images.py       # Composites 2D flat preview overlays using Pillow
├── juicy.py        # Matches colors between 3D renders and 2D overlays
└── cli.py          # fire + rich CLI

Test

uv run pytest -q

License

MIT.