# RigidWorld

> Manim-physics' Space and SpaceScene.

Page: https://fframes-kit.pages.dev/docs/physics/rigid-world/
Cargo feature: `physics` (`fframes-kit = { version = "..", features = ["physics"] }`)

Manim-physics' `Space` and `SpaceScene`. `RigidMotion::new(bodies, gravity, seconds)` runs
[rapier](https://rapier.rs) once at 60 steps a second, in the video's constructor. The same
bodies give the same motion every time (`enhanced-determinism`). A `Body` is
`Body::circle`, `Body::rect`, `Body::polygon` (the convex hull of its points) or
`Body::wall(a, b, thickness)`, which is fixed. It is set up with `velocity`, `spin`,
`angle`, `fixed`, `restitution`, `friction`, `density` and `color`. `poses(t)` gives every
body's `Pose` (`x`, `y`, and an `angle` that counts whole turns). `RigidWorld` draws the
bodies, filled and outlined, with a radius on circles that shows them turning. Its `draw`
closure gets a `BodyView` (index, center in pixels, rotation in degrees for SVG `rotate()`,
pixels per unit) and returns its own drawing, or `None` to keep the default. Rapier adds
about 2 MB to an editor bridge built with `physics`. Gallery scene: `RigidWorld`.

Gallery clip of `RigidWorld`: https://fframes-kit.pages.dev/media/scenes/RigidWorld-b2f3e4d1.mp4

```rust
use fframes_kit::prelude::*;

struct Video {
    world: RigidMotion,
}

impl Video {
    fn new() -> Self {
        let bodies = vec![
            Body::wall((-6.0, -3.0), (6.0, -3.0), 0.3),
            Body::circle(-2.0, 2.0, 0.4).velocity(1.5, 0.0).restitution(0.8),
            Body::rect(1.0, 1.0, 1.0, 0.6).angle(0.4),
        ];
        Self {
            world: RigidMotion::new(bodies, (0.0, -9.81), 5.0),
        }
    }

    fn figure<'a>(&'a self, ui: &mut Ui<'a, '_, '_>) -> Svgr<'a> {
        ui.show(RigidWorld {
            motion: Some(&self.world),
            ..ui.defaults()
        })
    }
}
```

## API

Components are plain structs. Set the fields you need and fill the rest with `..ui.defaults()`: the defaults below come from the current theme (`theme.` values are fields of `Theme`).

### RigidWorld

| Field | Type | Default | Description |
| --- | --- | --- | --- |
| `motion` | `Option<&RigidMotion>` | `None` | The simulated bodies to draw, built once in the video's constructor; `None` draws nothing. |
| `delay` | `f32` | `0.0` | Seconds after the local start before the simulation starts to play. |
| `time_scale` | `f32` | `1.0` | Speed of the motion over local time; 2 runs twice as fast, 1 is real time. |
| `draw` | `Option<DrawBody>` | `None` | Draws a body in your own way: a closure given its `BodyView` that returns the picture, or `None` to leave it to the default shape. |
| `fill_color` | `Color` | `theme.colors.accent` | Fill of a body that has no colour of its own. |
| `fixed_color` | `Color` | `theme.colors.muted` | Fill of fixed bodies such as walls. |
| `stroke_color` | `Color` | `theme.colors.text` | Colour of the outline, and of the radius that shows a circle turning. |
| `stroke_width` | `f32` | `theme.stroke.thin` | Outline width in pixels. |
| `enter` | `Option<FadeIn>` | `None` | Fade in at the start; `None` for none. |
| `exit` | `Option<FadeOut>` | `None` | Fade out before the end; `None` for none. |

Feature `physics` · [Source](https://github.com/khanhthanhdev/fframes-kit/blob/main/fframes-kit/src/kits/physics/rigid.rs#L349)