Question

I’m working on a little side project and having a little difficulty getting a steering algorithm to work well in ThreeJS with the Object3D positioning. The main issue I seem to be having currently is the angular velocities are rather uncontrolled, everything rotates way too quickly. I’d like to be able to limit this a bit. I’m providing a simplified example of the code. I think I’m almost there, and I’ve looked a bit at quaternions and Matrix4 but couldn’t figure it out. Anyone had this issue before? Thanks!

class Movement extends THREE.Object3D
    constructor: ->
        super
        @velocity = new THREE.Vector3()
        @speed = 4
        @ease = 7
        @hault = 2

    steer: (mode, target) ->
        if @speed is 0
            @velocity.set 0, 0, 0
            return true

        # velocity vector
        switch mode
            when 'arrive'
                fromPosition = @position
                toPosition = target
            when 'flee'
                fromPosition = target
                toPosition = @position
        @velocity.sub toPosition, fromPosition

        # calculate magnitude
        magnitude = @velocity.length()

        # hault
        if magnitude < @hault
            return true

        # limit angle of rotation
        # angle = Math.acos fromPosition.dot(toPosition) / fromPosition.length() / toPosition.length()
        # axis = new THREE.Vector3().cross fromPosition, toPosition .normalize()

        # speed limit
        if magnitude > @speed
            @velocity.divideScalar magnitude / @speed

        # easing
        if magnitude < @ease and mode is 'arrive'
            @velocity.multiplyScalar magnitude / (@ease + @hault / 2)

        # adjust for time
        @velocity.multiplyScalar GLOBAL.clock.getDelta()

        # update position and rotation
        @position.addSelf @velocity
        @rotation.y = Math.atan2 -@velocity.z, @velocity.x
        @rotation.z = Math.asin @velocity.y / @velocity.length()

Answer 1

Try and modify this:

var qstart = new THREE.Quaternion();
    var qend = new THREE.Quaternion();
    var m  = new THREE.Matrix4();

    qstart.setFromRotationMatrix( MOVING_OBJECT.matrixWorld );
    qend.setFromRotationMatrix( m.lookAt( TARGET.position, MOVING_OBJECT.position, new THREE.Vector3( 0, 1, 0 ) ) );  

    MOVING_OBJECT.rotation.setEulerFromQuaternion( qstart.slerpSelf(qend, 0.015 ) );