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README: Link to and spell-out SDF #30

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Jan 12, 2024
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README: Link to and spell-out SDF #30

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6 changes: 4 additions & 2 deletions README.md
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Expand Up @@ -5,7 +5,7 @@
[![crates.io](https://img.shields.io/crates/d/bevy_smud.svg)](https://crates.io/crates/bevy_smud)
[![docs.rs](https://img.shields.io/docsrs/bevy_smud)](https://docs.rs/bevy_smud)

Sdf 2d shape rendering for [Bevy](https://bevyengine.org).
[Signed_Distance_Field/Function][SDF] (SDF) 2D shape rendering for [Bevy](https://bevyengine.org).

![screenshot of a bird drawn with bevy_smud](https://johanhelsing.studio/assets/bevy_smud_banner.png)

Expand All @@ -17,7 +17,7 @@ If you keep the number of different sdf and fill combinations relatively low it'

## Usage

A signed distance field (sdf) is a way to map points in space to distances to a surface. If a point maps to a positive value, it's outside the shape, if it's negative, it's inside the shape. These "mappings" can be described by functions, which takes a point as input and returns a distance to a surface. For instance, if you wanted to make a circle, it could be described as `length(position - center) - radius`. That way, all the points that are `radius` away from `center` would be 0 and would define the edge of the shape.
An SDF is a way to map points in space to distances to a surface. If a point maps to a positive value, it's outside the shape, if it's negative, it's inside the shape. These "mappings" can be described by functions, which takes a point as input and returns a distance to a surface. For instance, if you wanted to make a circle, it could be described as `length(position - center) - radius`. That way, all the points that are `radius` away from `center` would be 0 and would define the edge of the shape.

Many such functions describing geometric primitives are included in this library, they are imported automatically when using the single-expression or body shorthand for adding sdfs. For instance, the circle above could also be described as:

Expand Down Expand Up @@ -99,3 +99,5 @@ The `main` branch targets the latest bevy release.
## Thanks!

Little of this crate is original work. It's mostly a mishmash of [`bevy_sprite`](https://github.com/bevyengine/bevy/tree/main/crates/bevy_sprite) and [Inigo Quilez sdf rendering primitives](https://iquilezles.org/www/articles/distfunctions2d/distfunctions2d.htm) ported to wgsl. I just put the two together in a way I found convenient.

[SDF]: https://en.wikipedia.org/wiki/Signed_distance_function