pocketpy/docs/modules/box2d.md

icon	label
package-dependencies	box2d

!!! This module is optional. Set PK_USE_BOX2D to 1 to enable it. !!!

Box2D by Erin Catto, the world's best 2D physics engine now becomes a built-in module in pkpy v1.1.3 and later. All platforms are supported, including desktop, mobile and web.

Overview

The box2d module in pkpy provides a high-level, also simplified, interface to Box2D engine, which is suitable for most use cases. There are two classes in box2d module: World and Body.

World is the world of Box2D, it is the container of all Bodys. In most cases, you only need one World instance. World class provides methods to create, destroy and query Bodys and also methods to step the simulation.

A Body instance is a physical entity in the world. A Body can only have one shape at a time. For example, a circle, a rectangle, a polygon, etc. You are allowed to change the shape of a Body at runtime. Bodys can be static, dynamic or kinematic. A static Body is not affected by forces or collisions. A dynamic Body is fully simulated. A kinematic Body moves according to its velocity. Body class provides methods to set its properties, such as position, velocity, etc. It also provides methods to apply forces and impulses to it.

!!! A box2d.Body in pkpy is an unified wrapper of Box2D's b2Body, b2Shape and b2Fixture. It hides the details of Box2D's API and provides a high-level interface. !!!

APIs

https://github.com/blueloveTH/pocketpy/blob/main/include/typings/box2d.pyi

Example

import box2d
from linalg import vec2

# create a world
world = box2d.World()

# create a body with a box shape
body = box2d.Body(world)
body.set_box_shape(1, 1)

# give it a velocity
body.velocity = vec2(1, 0)

# step the simulation
for i in range(30):
    world.step(1/30, 8, 3)
    print(i, body.position)

0 vec2(0.033, 0.000)
1 vec2(0.067, 0.000)
2 vec2(0.100, 0.000)
3 vec2(0.133, 0.000)
4 vec2(0.167, 0.000)
5 vec2(0.200, 0.000)
6 vec2(0.233, 0.000)
7 vec2(0.267, 0.000)
8 vec2(0.300, 0.000)
9 vec2(0.333, 0.000)
10 vec2(0.367, 0.000)
11 vec2(0.400, 0.000)
12 vec2(0.433, 0.000)
13 vec2(0.467, 0.000)
14 vec2(0.500, 0.000)
15 vec2(0.533, 0.000)
16 vec2(0.567, 0.000)
17 vec2(0.600, 0.000)
18 vec2(0.633, 0.000)
19 vec2(0.667, 0.000)
20 vec2(0.700, 0.000)
21 vec2(0.733, 0.000)
22 vec2(0.767, 0.000)
23 vec2(0.800, 0.000)
24 vec2(0.833, 0.000)
25 vec2(0.867, 0.000)
26 vec2(0.900, 0.000)
27 vec2(0.933, 0.000)
28 vec2(0.967, 0.000)
29 vec2(1.000, 0.000)