voxel-physicals
v0.2.1
Published
create objects that have aabbs and respond to accel and vel updates
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voxel-physicals
Create voxel-js objects that are affected by physics! Based on chrisdickinson's voxel-physical except replaces the three.js dependency with gl-matrix, for use with voxel-engine-stackgl.
// 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-physicals')
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 theacceleration
orvelocity
-- 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 ofstate.forward = true
, etc, over several frames.
LICENSE
MIT