voxel-physical

create objects that have aabbs and respond to accel and vel updates

npm install voxel-physical
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voxel-physical

create voxel-js objects that are affected by physics!

// typical usage:
var game = require('voxel-engine')({})
  , object = new THREE.Mesh()

var physics = game.makePhysical(object)
game.addItem(physics)
game.scene.add(object)

// direct usage:
var physical = require('voxel-physical')

var physics = physical(
    object
  , game.potentialCollisionSet()    // list of objects providing a `collide(otherObject, otherBBox, desiredVector, resting map)

  , new THREE.Vector3(10, 10, 10)   // how big am i? w/h/d
  , new THREE.Vector3(30, 5.6, 30)  // what's my terminal velocity?
) 

game.addItem(physics)
game.scene.add(object)

API

physics.aabb() -> aabb-3d instance

Create a bounding box for the physics.

physics.subjectTo(vec3 force) -> physics

State that the object is subject to this force every frame -- i.e., gravity.

physics.avatar -> THREE.Mesh / THREE.Object3D

The target of the physics. All physics are applied in this object's world space (so, if you have a player, they're comprised of yaw, pitch, and roll Object3D instances along with meshes -- roll and pitch are contained by yaw, so yaw is the outermost object in this case.)

physics.resting -> {x: [-1, 0, 1], y: [-1, 0, 1], z: [-1, 0, 1]}

physics.atRestX() -> [-1, 0, 1]

physics.atRestY() -> [-1, 0, 1]

physics.atRestZ() -> [-1, 0, 1]

Describes each of the local axises and whether or not the object is resting in that local axis (and in what direction).

physics.acceleration -> THREE.Vector3

The avatar's current acceleration in local space (or change in velocity over a frame).

physics.velocity -> THREE.Vector3

The avatar's current velocity in local space (or change in position over a frame).

physics.friction -> THREE.Vector3

The degree by which to scale velocity on each axis for a given frame. Reset to 1.0 during physics.tick(dt) before the collisions for this frame are calculated and applied. Colliding objects may change the object's friction in any one of the axises during their collide call.

physics.tick(dt)

Called by voxel-engine.

For each axis, acceleration is calculated (accel/8 + forces.x); acceleration is applied to velocity ((velocity + accel) / friction), and a desired local vector is created from velocity (vel > terminal ? terminal : val).

Then a world desired vector is created from that local desired vector. Friction is reset to 1.0. Resting state for all axis is reset to 0. Then, the potential collision set is iterated, and those calls receive the physics object, the world desired vector, the current bounding box, and the current resting state, and are expected to modify these variables when there is a collision (i.e., when we collide with terrain, the friction is modified on opposite axes from the collision; we set the resting state of the object on the colliding axis to the "direction" of impact, and we modify the desired world vector to implement the collision).

tiny tips

  • Don't modify physics.avatar.position directly! Prefer to modify the acceleration or velocity -- this gives you much more realistic looking motion.

  • Remember, all of the force/accel/velocity/friction/resting states are in local space, not world space. Collisions happen in world space. You have to translate back to local space to apply changes.

As a concrete example, the voxel avatar's player is governed by a physics object attached to the yaw (the rotation around the Y axis -- looking left and right). So, our physics attributes look like this:

local space                 world space

      -z                      -lz    +lx 
      ^                         \  /
      |                          \/
-x <-----> +x                    /\
      |                         /  \
      V                      -lx    +lz 
      +z

Which is to say, the rotation of yaw affects the world vectors described by the local physical attributes of your player!

  • Use voxel-control to implement AI/etc. Instead of describing motion in terms of movements, you can describe motion in terms of state.forward = true, etc, over several frames.

LICENSE

MIT

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