bonk-docs/content/shapes/overview.md

---
title: "Overview"
date: 2019-09-14T19:19:03-07:00
weight: 5
---

In Bonk, an *IShape2D* is defined by two methods.

1) A *support function*, which is a method that returns the farthest possible point in the shape in a given *Vector2* direction. The shape vertices are transformed by a *Transform2D*.

2) A method for creating an axis-aligned bounding box from the shape that takes a *Transform2D* to transform the shape vertices.

Bonk provides you with tested implementations of four common 2D shapes, but you can implement these methods to create custom *IShape2D* structs.

Note that shapes themselves do not contain absolute position data. You will use a *Transform2D* to manipulate the shape's position, rotation, and scale in 2D space.

A final restriction to note: Defining concave shapes is an error. The collision solving algorithm that Bonk uses does not support concave shapes. If you wish to define concave shapes, define them as a composition of multiple convex shapes.
initial commit 2019-09-15 02:55:02 +00:00			`---`
color changes and renaming 2019-09-15 05:03:47 +00:00			`title: "Overview"`
initial commit 2019-09-15 02:55:02 +00:00			`date: 2019-09-14T19:19:03-07:00`
			`weight: 5`
			`---`

writing about transforms 2019-09-15 06:39:26 +00:00			`In Bonk, an IShape2D is defined by two methods.`
initial commit 2019-09-15 02:55:02 +00:00
writing about transforms 2019-09-15 06:39:26 +00:00			`1) A support function, which is a method that returns the farthest possible point in the shape in a given Vector2 direction. The shape vertices are transformed by a Transform2D.`
initial commit 2019-09-15 02:55:02 +00:00
writing about transforms 2019-09-15 06:39:26 +00:00			`2) A method for creating an axis-aligned bounding box from the shape that takes a Transform2D to transform the shape vertices.`
initial commit 2019-09-15 02:55:02 +00:00
writing about transforms 2019-09-15 06:39:26 +00:00			`Bonk provides you with tested implementations of four common 2D shapes, but you can implement these methods to create custom IShape2D structs.`
initial commit 2019-09-15 02:55:02 +00:00
writing about transforms 2019-09-15 06:39:26 +00:00			`Note that shapes themselves do not contain absolute position data. You will use a Transform2D to manipulate the shape's position, rotation, and scale in 2D space.`
initial commit 2019-09-15 02:55:02 +00:00
			`A final restriction to note: Defining concave shapes is an error. The collision solving algorithm that Bonk uses does not support concave shapes. If you wish to define concave shapes, define them as a composition of multiple convex shapes.`