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https://github.com/bfanger/svelte-cannon
Declarative Svelte components for the cannon-es physics engine
https://github.com/bfanger/svelte-cannon
cannon-es physics-simulation svelte
Last synced: 3 months ago
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Declarative Svelte components for the cannon-es physics engine
- Host: GitHub
- URL: https://github.com/bfanger/svelte-cannon
- Owner: bfanger
- License: mit
- Created: 2021-12-29T15:39:18.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2022-10-09T16:04:19.000Z (about 2 years ago)
- Last Synced: 2024-10-14T09:37:38.547Z (3 months ago)
- Topics: cannon-es, physics-simulation, svelte
- Language: Svelte
- Homepage: https://svelte-cannon.bfanger.nl/
- Size: 2.19 MB
- Stars: 20
- Watchers: 3
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: Readme.md
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README
# Svelte Cannon
Use [Svelte](https://svelte.dev/) components to build a [cannon-es](https://pmndrs.github.io/cannon-es/) physics simulation.
## Installation
```sh
npm install svelte-cannon # or yarn add svelte-cannon
```
## Usage
This example uses [svelte-cubed](https://svelte-cubed.vercel.app/) to display the objects, but svelte-cannon is renderer engine agnostic.
```svelte
import * as CANNON from "cannon-es";
import * as PE from "svelte-cannon";
import * as THREE from "three";
import * as SC from "svelte-cubed";
let position = new CANNON.Vec3(0, 4, 0);
```
Using the import `* as PE` is helpfull to avoid naming conflicts, [three](https://threejs.org/docs/#api/en/math/Sphere), [cannon-es](https://pmndrs.github.io/cannon-es/docs/classes/Sphere.html) and [svelte-cannon](./src/lib/components/Sphere.svelte) all export a `Sphere` for example.
_(PE is short for **P**hysics **E**ngine)_
Generally you'd want the nest the `SC.Canvas` inside the `PE.World`, because that allows subcomponents to create both the physics engine and the render engine components.
## Shorthand notations
Allowed values for setting a 3D vector are:
- `[1, 2, 3]`
- `new CANNON.Vec3(1, 2, 3)`
- `new THREE.Vector3(1, 2, 3)`
- `{x: 1, y: 2, z: 3}`
This allows for reusing existing variables and reduces boilerplate.
## Two way binding caveats
1. `bind:property=` for 3D vectors only works when an `CANNON.Vec3` object is passed.
This restriction allows svelte-cannon to detect which properties you're interested in.
Due to the nature of physics engines a lot of properties could change every on frame, recalculating the `velocity` of the ground plane would be wasteful.
2. When the body is awake `bind:property=` will trigger updates, but the value might not have changed.
Syncing position the THREE.Mesh is a fast operation.
`$: mesh.position.copy(position);` ( CANNON.Vec3 is compatible with THREE.Vector3 )
Creating shadow values, recalculating and checking and for changes would be overhead.
## Imprecise stores
`writableVec3` creates store, but when you're setting the value with a CANNON.Vec3 that has roughly the same value it won't trigger an update.
```svelte
import * as PE from "svelte-cannon";
import * as SC from "svelte-cubed";
const position = PE.writableVec3(0, 4, 0);
position.precision = 0.001; // 1mm (default)
```
This allows you to prevent resending values to the renderer that haven't changed.
From a usage perspective it acts as a `writable(new Vec3(0, 4, 0))` but also allows shorthand notations:
- `position.set(1, 2, 3)`
- `position.set(new CANNON.Vec3(1, 2, 3))`
- `$position = new CANNON.Vec3(1, 2, 3)`
- `$position = new THREE.Vector3(1, 2, 3)`
- `$position = {x: 1, y: 2, z: 3}`
- `$position = [1, 2, 3]`
- `$position.x = 1; $position.x = 2; $position.x = 3;`
## Forces and Constraints
As bodies can have multiple constrains and forces can affect multiple bodies it doesn't translate well to a component hierarchy. HTML also has this problem with ``s and ``s, svelte-cannon approach is based on the `id=` and `for=` solution:
```svelte
...
```
Note: These id's not related the numerical id's of the cannon-es Bodies.
## Contributing
### Setup
```sh
yarn install
yarn dev
```
### Linting
```sh
yarn lint # or npm run lint
```
### Build
```sh
yarn package # or npm run package
```