Entity Physics

Simple entity physics simulation for game worlds. This project is still a work-in-progress.

This project forked from brunodb3/entity-physics

Usage

Install the package to your project:

$ npm install --save @saintdoggie/entity-physics
# or
$ yarn add @saintdoggie/entity-physics

Then add it to your game client/server:

import { Physics } from "@saintdoggie/entity-physics";

// Instantiate the Physics processor
const physics = new Physics();

// Set tick rate to be 60 fps
setTimeout(() => {
 physics.tick();
}, 1000 / 60);

You can add entities to the physics processor and add forces to those entities. Their kinematics will be calculated at every tick (velocity, position, direction...):

import { Physics, Entity } from "@saintdoggie/entity-physics";

const physics = new Physics();

// All vectors are Victor from the Victor package.
// Entities start with `entity.kinematics.velocity = { x: 0, y: 0, z: 0 }`
const someEntity = new Entity("some-id");

// If you want an entity to be processed at every tick, you need to add it to
// the `entities` array in the physics processor
physics.entities.addEntity(someEntity);

// All forces are multiplied by the `deltaTime`, allowing for multiple framerates
// without compromising the actual processing of the entities
// (at 20fps the position will be the same as at 60fps)
someEntity.addForce({ x: 1, y: 0 });

The force calculations are as follows:

newForce = newForce * acceleration; // multiply by acceleration for smoother movement
velocity = velocity + newForce; // add the new force to the velocity
velocity = velocity * frictionMultiplier; // multiply the velocity by a friction multiplier, in order for the entity to stop when the force is 0

Entities can have different rates for acceleration, maximum/minimum velocity lengths amongst other options:

const entity = new Entity('some-id', {
  runningMultiplier: 1.5, // when running, the force is multiplied by this value
  minVelocity: 0.5,
  maxVelocity: 9.5,
  acceleration: 0.7,
  frictionMultiplier: 0.9
  ...
});

For more information on how to use the library, see the .spec files, as they provide working examples.