Modify time scale in 2D physics engine

[TheTrope]

Hi,

I would like to modify time scale in a 2D physics engine. I searched about it, and matter.js seems to permit timescale modification.

In addition, i would like to set 'different timescales' for different bodies (as example: 2 object fall, one will be set to timescale:1 and the other timescale:0.5. So this last one will fall 2x slowly)

It sound nonsense, but is there a trick to do it?

I thouth about saving positions on last step, and compare them to the new one, then replacing them with a homothety value relative to the timescale. But there is a lot of cases that this can't handle

Any sugestions?

Thanks

[away168]

I may not be able to answer your question, but maybe this link may help you to find your answer: http://gafferongames.com/game-physics/fix-your-timestep/

[hotfeet]

an old post but couldn't you apply an update rate to the object and use that to calculate when it should do stuff? something like

function obj(x, y, updateRate) {
    this.position = new vector2(x, y);
    this.velocity = new vector2(0, 0);
    this.acceleration = new vector2(0, 0);
    this.maxSpeed = 4;
    this.updateTime = 0;
    this.updateRate = updateRate;
    this.updateLast = 0;
}

obj.prototype.addForce = function(fx, fy) {
    this.acceleration.x = fx;
    this.acceleration.y = fy;
}

obj.prototype.update = function(step) {
    this.updateTime += step;
    if(this.updateTime - this.updateLast > this.updateRate) {
        //do your update
        this.velocity.add(this.acceleration);
        this.acceleration.zero();
        this.velocity.limit(this.maxSpeed);
        this.position.add(this.velocity);
        this.updateLaste = this.updateTime;
    }
}

but really couldn't you do this without changing "time scales" and just limit the velocity or simply apply a different force to each object