# Path Manipulation

General path manipulation can be performed on the [Polygon](https://docs.rs/valora/0.2.0/valora/forms/struct.Polygon.html) type. We can construct a `Polygon` from any type implementing `Iterator<Item=P2>`, which `Ngon` does.

```rust
let square = Polygon::from(Ngon::square(world.center(), 200.));
canvas.paint(Filled(square));
```

![](/files/-LwFj-eZqsVQE2cc9w8B)

`Polygon` provides an iterator over its vertices we can use to manipulate them, and build a new polygon. In this code we use that to distort the polygon by sampling [Fbm](https://docs.rs/valora/0.2.0/valora/prelude/struct.Fbm.html) noise with time as the `z` position:

```rust
let fbm = Fbm::new().set_seed(world.seed as u32);
let shift_by_timed_noise = |v| {
    let sample_point = P3::new(v.x, v.y, ctx.time.as_secs_f32().sin() / 5.);
    let t = fbm.noise(sample_point) * 60.;
    v.translate(V2::new(t, t))
};

let square = Polygon::from(Ngon::square(world.center(), 200.));
let square = Polygon::from(square.vertices().map(shift_by_timed_noise));
```

![A square whose vertices are translated by noise.](/files/-LwFp2xqbzfSnzNr3BNp)

Further, we can iteratively subdivide and apply this same distortion to make more interesting shapes:

```rust
let fbm = Fbm::new().set_seed(world.seed as u32);
let shift_by_timed_noise = |(v, strength): (P2, f32)| {
    let sample_point =
        P3::new(v.x / 100., v.y / 100., ctx.time.as_secs_f32().sin() / 2.);
    let t = fbm.noise(sample_point) * strength;
    v.translate(V2::new(t, t))
};

let square = Polygon::from(Ngon::square(world.center(), 200.));
let initial_strength = 15.;
let splotches =
    std::iter::successors(Some((square, initial_strength)), |(shape, strength)| {
        let next_strength = strength / 1.5;
        let next_shape = Polygon::from(
            shape
                .clone()
                .subdivide()
                .vertices()
                .map(|v| (v, *strength))
                .map(shift_by_timed_noise),
        );
        
        Some((next_shape, next_strength))
    })
    .map(|(s, _)| s);

for splotch in splotches.skip(8).take(1) {
    canvas.paint(Filled(splotch));
}
```

![An animated low-poly cloth.](/files/-LwFshZfKc6vajC0PQ-i)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://paytonturnage.gitbook.io/valora/path-manipulation.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.