BrownianTransformer.java

package jo.vecmath.logic;

import java.util.Random;

import jo.vecmath.Matrix4f;
import jo.vecmath.Point3f;

public class BrownianTransformer implements ITransformer {

    private Random mRND;
    private Point3f mLocation;
    private Point3f mTarget;
    private float mVelocity; // per second
    private float mRadius;
    private long mLastTick;

    public BrownianTransformer(float velocity, float radius) {
        mVelocity = velocity;
        mRadius = radius;
        mRND = new Random();
        mLastTick = System.currentTimeMillis();
        mLocation = new Point3f(0, 0, 0);
        newTarget();
    }

    private void newTarget() {
        mTarget = new Point3f(newDelta(), newDelta(), newDelta());
    }

    private float newDelta() {
        return (mRND.nextFloat() - .5f) * mRadius * 2;
    }

    @Override
    public Matrix4f calcTransform(Matrix4f transform) {
        long now = System.currentTimeMillis();
        float elapsed = (now - mLastTick) / 1000f;
        float traverse = elapsed * mVelocity;
        for (;;) {
            float dist = mTarget.distance(mLocation);
            if (traverse < dist) {
                break;
            }
            traverse -= dist;
            mLocation.set(mTarget);
            newTarget();
        }
        Point3f delta = new Point3f();
        delta.sub(mTarget, mLocation);
        Point3fLogic.normalize(delta);
        delta.scale(traverse);
        mLocation.add(delta);
        Matrix4f newTrans = new Matrix4f(transform);
        newTrans.m03 += mLocation.x;
        newTrans.m13 += mLocation.y;
        newTrans.m23 += mLocation.z;
        mLastTick = now;
        return newTrans;
    }
}