Boxed Physics
Boxed Physics is an extension for Scratch 3 that allows you to add 2D physics simulations to your Scratch projects.
This documentation will guide you through the process of using Boxed Physics.
Startup & world options
When using the Boxed Physics extension, you always need to initialise the environment when starting the project. to do this, you can use the Init World, scale 1m: [SCALE] gravity: [GRAVITY] scene: [SCENE] block.
Scene is the type of containment to keep objects within the stage:
- boxed stage: Keeps sprites from going off the bottom and sides.
- closed stage: Keeps sprites from going off the bottom, sides, or top.
- opened stage: Keeps sprites from going off the bottom.
- nothing: Removes all walls so objects can go wherever they want.
- stage: a depricated option that is the same as boxed stage.
You can move forward in time using the step simulation block. Run this in a loop to keep the physics going.
This next block lets you set the physics options. You usually won't need to use this block.
You can also set the speed of the world with the set slow motion block.
You can also get the slow motion value with the get slow motion block.
Making objects
Making objects requires that you define an object first, so running this does nothing on its own.
Define an object type first, then the object itself. Now, you can place it in the world.
You can do the steps in any order, just Create the object body last.
Defining types
Types allow you to make objects with spesific properties.
Making a box
Making a box is simple, just define the box, then create the body.
Making a circle
Making a circle is just as simple, Use the code from the box, and replace it with the circle making block.
Making pollygons
Thare are two ways of making a pollygon object. You can eather use the Define pollygon as this costume block, or the Define Polygon, points: [POINTS] block.
Define pollygon as this costume lets you use the costume of a sprite to make a pollygon, while
Define Polygon, points: [POINTS] lets you defide a pollygon manually.
Every point in a pollygon is seperated by 3 spaces. Every point has only one space from x to y.
Destroying objects
You can destroy an object by simply providing its name into the destroy block.
Updating collision
You can make objects not collide with eachother using collision groups.
The objects in here will be in their own no-collide group, and will collide with everything else.
You can also remove no-collide tags from objects
Damping
You can set the damping or the rotational damping of an object.
Moving objects
Thare are a two ways to move your objects. you can push them, or you can set their movement directly.
You can push your objects using inpulses, or World Impulses.
You can also set the velocity of an object directly, or remove it entirely.
While I'm at it, I might as well mention these blocks
Object attributes
You can get the attributes of any object using the (get [thing] from [object]) block.
You can get the following from an object:
- X
- Y
- Direction
- X velocity
- Y velocity
- Directional velocity
- Is awake?
You can also get the object at any position with this:
Making joints
Joints are another thing built into Boxed Physics. Just like objects, they need to be defined before you can place them.
Thare are Rotating, Spring, Weld, Slider, and Mouse jonts built into Boxed Physics, but more are on the way.
Thare are only two joints that need extra info to define them, being springs and sliders.
Making a spring
Springs are made of three values: Length, Damping, and Frequency.
Making a slider
Sliders are another type of joint is a slider joint. Sliders are made with a direction, lower stop, and an upper stop.
Editing joints
You can edit joints using the Set [attr] of [joint] block to set attributes of joints.
You can set the following:
- Motor On
- Motor Speed
- Max Torque
- Limits On
- Lower Limit
- Upper
Getting joint attributes is just as easy.
You can also delete joints.
If you made a mouse joint, you can edit the target position with this block.