BB.Particle2D

Defined in: src/BB.Particle2D.js:13

A 2D Particle class for all your physics needs

Index

Properties

Methods

Constructor

BB.Particle2D
(
  • [config]
)

Defined in src/BB.Particle2D.js:13

Parameters:

  • [config] Object optional

    An optional config object to initialize Particle2D properties, including: position ( object with x and y ), mass ( defaults to 1 ), radius ( defaults to 0 ) and friction ( defaults to 1 ).

    an initial velocity or acceleration can also be set by passing a BB.Vector2 to either of those properties ( ie. velocity or acceleration ). Or an alternative approach is to initialize with a heading property (radians) and speed property ( number ). If no velocity or acceleration or heading/speed is set, the default velocity is BB.Vector2(0,0).

Example:

  var WIDTH = window.innerWidth;
  var HEIGHT = window.innerHeight;

  var star = newBB.Particle2D({
     position: new BB.Vector2(WIDTH/2, HEIGHT/2 ),
     mass: 20000
 });

  var planet = new BB.Particle2D({
     position: new BB.Vector2( WIDTH/2+200, HEIGHT/2),
     heading: -Math.PI / 2,
     speed: 10
  });

  var comet = new BB.Particle2D({
     position: new BB.Vector2(
         BB.MathUtils.randomInt(WIDTH),
         BB.MathUtils.randomInt(HEIGHT) ),
     velocity: new BB.Vector2(
         BB.MathUtils.randomInt(10),
         BB.MathUtils.randomInt(10))
  });

Properties

acceleration BB.Vector2

Defined in src/BB.Particle2D.js:99

Usually used to accumulate forces to be added to velocity each frame

elasticity Number default:0.05

Defined in src/BB.Particle2D.js:135

how bouncy it is when it collides with an object

friction Number default:1

Defined in src/BB.Particle2D.js:128

the particle's friction ( not environment's friction ) multiplied by velocity each frame

heading Number

Defined in src/BB.Particle2D.js:154

the particle's "heading" expressed in radians, essentially: Math.atan2( velocity.y, velocity.x );

mass Number default:1

Defined in src/BB.Particle2D.js:114

the particle's mass

radius Number default:0

Defined in src/BB.Particle2D.js:121

the particle's radius, used for callculating collistions

speed Number

Defined in src/BB.Particle2D.js:169

the particle's "speed", essentially: the square root of velocity.x² + velocity.y²

velocity BB.Vector2

Defined in src/BB.Particle2D.js:56

the particle's velocity ( see acceleration also )

There are no properties that match your current filter settings. You can change your filter settings in the index section on this page. index

Methods

applyForce
(
  • vector
)

Defined in src/BB.Particle2D.js:563

takes a force, divides it by particle's mass, and applies it to acceleration ( which is added to velocity each frame )

Parameters:

collide
(
  • config
)

Defined in src/BB.Particle2D.js:375

tracks objects to collide against, this can be other particles ( objects with position vectors and a radius ) and/or a perimeter ( top, left, right, bottom )

Parameters:

  • config Object

    object with properties for top, left, bottom, right ( all numbers ) and particles ( array of other particles or objects with position.x, positon.y and radius properties )

Example:

  // assuming ball is an instance of BB.Particle2D
  // assuming balls is an array of BB.Particle2D objects
  ball.collide({
     top:0,
     right: canvas.width,
     bottom: canvas.height,
     left: 0,
     particles: balls
  });

gravitate
(
  • particle
  • [mass]
)

Defined in src/BB.Particle2D.js:187

identifies something to gravitate towards. the object of gravitation needs to have a position ( x, y ) and mass

Parameters:

  • particle Object

    if passed as the only argument it should be an Object with a position.x, position.y and mass ( ie. an instance of BB.Particle2D ). Otherwise the first argument needs to be an Object with an x and y ( ie. instance of BB.Vector2 or at the very least { x: ..., y: ... } )

    alternatively, gravitate could also be passed an array of objects ( each with position and mass properties )

  • [mass] Number optional

    when particle is not an instance of BB.Particle2D and is a Vector an additional argument for mass is required

Example:

  // assuming star and planet are both instances of BB.Particle2D
  planet.gravitate( star );
  // or
  planet.gravitate( star.position, star.mass );
  // or
  planet.gravitate( { x:WIDTH/2, y:HEIGHT/2 }, 20000 );

  // assuming stars is an array of BB.particle2D
  planet.gravitate( stars );

spring
(
  • config
)

Defined in src/BB.Particle2D.js:289

identifies something to spring towards. the target needs to have an x,y position, a k value which is a constant factor characteristic of the spring ( ie. its stiffness, usually some decimal ), and a length.

Parameters:

  • config Object

    object with properties for point ( vector with x,y ), k ( number ) and length ( number ).

    alternatively, spring could also be passed an array of config objects

Example:

  // assuming ball is an instance of BB.Particle2D
  // and center is an object with x,y positions
  ball.spring({
     position: center.position,
     k: 0.1,
    length: 100
  });
 
  // the ball will spring back and forth forever from the center position
  // unless ball has friction value below the default of 1.0

update ()

Defined in src/BB.Particle2D.js:440

Update the particle's internals and apply acceleration to veloicty. Called once per animation frame.

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