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css-matrix-calc/README.md
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# CSS Matrix3D Perspective Calculator
A browser-based tool for generating CSS `matrix3d()` transforms with perspective projection. Define 4 corners on a field and a widget size — get ready-to-use CSS code.
**Keywords:** CSS matrix3d, perspective transform, 3D CSS, homography, quadrilateral mapping, CSS transform generator, perspective projection, CSS 3D effects
## Usage
Open `index.html` in a browser (no build step required).
- **Edit** — drag corners on the SVG field, adjust field and widget sizes
- **Preview** — see the live matrix3d() transform result
Copy the CSS from the "CSS Output" section and paste into your project.
## Features
- Pure math — homography-based matrix3d() calculation
- Live preview with real-time updates
- Drag-and-drop corner positioning
- Editable field dimensions with aspect ratio lock
- Rescale coordinates option when resizing the field
- Zero dependencies, runs in any modern browser
## Use Cases
- **Presentations & landing pages** — render a widget or screenshot on a monitor at any angle
- **Carousels & galleries** — show product cards with perspective deformation
- **Interactive infographics** — overlay data on maps or charts with perspective
- **App previews** — place mobile UI on a device background
- **Scroll-based effects** — animate matrix3d for 3D effects without WebGL
- **Mockups & prototypes** — visually place interfaces in context (on a wall, laptop, banner)
## Project Structure
```text
├── index.html
├── style.css
└── js/
├── main.js — entry point
├── state.js — state management
├── homography.js — homography math
├── svg-renderer.js — SVG rendering
├── drag.js — drag handling
├── inputs.js — input fields
├── preview.js — live preview
└── ui.js — buttons and modes
```
## How It Works
The tool uses [homography](https://en.wikipedia.org/wiki/Homography_(computer_vision)) to compute a 3D perspective transform from 4 corresponding points. The resulting `matrix3d()` CSS property maps a rectangular widget onto an arbitrary quadrilateral defined by the user.
## License
MIT