Issue with applying physics

[Sapper]

function AddPlayer (uname, startX, startY, player, game) {    var x = startX;    var y = startY;    //add player sprite    this.player = game.add.sprite(x, y, 'players');        //scale player down to appropriate size    this.player.scale.x = .4;    this.player.scale.y = .4;    this.player.anchor.set(0.5, 0.5);        // give other players physics    game.physics.arcade.enable(this.player);        // user info    this.game = game;    this.health = 3;    this.alive = true;    this.new_x = null;    this.new_y = null;        //assign 'name' bar above character    this.name = uname;    this.player.dname = game.add.text(x, y, this.name, { font: "12px Arial", fill: "#330088", align: "center" });    console.log('Added player to client: '+this.name);    this.lastPosition = { x: x, y: y }    };

When I apply the arcade physics, the sprite seems to shoot off the game world in a matter of milliseconds. The sprite isn't in contact with anything else. the AddPlayer() function is being pushed when I receive new information from the socket server. Any ideas?

[Edricus]

Does your world happen to have a gravity set on it?

[Sapper]

No, I haven't touched gravity at all.

[lewster32]

This usually happens because the sprite is not added at the expected phase of the frame (each frame has an execution order where physics are calculated, objects are moved and then rendered in order) and then moved due to anchor or scale being applied, and the movement is interpreted as a sudden change in velocity. Maybe try setting the anchor first, then the scale? Also, try doing this.player.velocity.set(0) at the end - though this may not work for the same reason the object is flying off in the first place.

 

A better way to do this would be to have the creation or enabling of physics deferred to the update loop, so you could maybe keep an array of initialised players, and in the update loop, check that array - if there are any in the array, enable physics on each and remove them from the array.

[Sapper]

This usually happens because the sprite is not added at the expected phase of the frame (each frame has an execution order where physics are calculated, objects are moved and then rendered in order) and then moved due to anchor or scale being applied, and the movement is interpreted as a sudden change in velocity. Maybe try setting the anchor first, then the scale? Also, try doing this.player.velocity.set(0) at the end - though this may not work for the same reason the object is flying off in the first place.

 

A better way to do this would be to have the creation or enabling of physics deferred to the update loop, so you could maybe keep an array of initialised players, and in the update loop, check that array - if there are any in the array, enable physics on each and remove them from the array.

 

Well, I attempted to use both of your suggestions, but to no avail. For curiosity purposes I tried applying the P2 physics system instead of Arcade and that worked flawlessly, but I'm not really looking to use P2 as everything else in my game uses Arcade. I'm stumped!

[lewster32]

I think in general, it's expected that sprites are created and have their physics applied within the update phase of the frame execution. The deferred method may be best for your situation. That or create a pool of dead player sprites with physics enabled in the create method, then rather than adding the sprite in your AddPlayer method, just grab one from the pool and revive it.

[Sapper]

I think in general, it's expected that sprites are created and have their physics applied within the update phase of the frame execution. The deferred method may be best for your situation. That or create a pool of dead player sprites with physics enabled in the create method, then rather than adding the sprite in your AddPlayer method, just grab one from the pool and revive it.

 

Thanks for your help. I used your suggestion for using an array to apply physics and while it didn't work before, I added this.player.body.reset() (see code) after applying the physics and now it works perfectly.

    for (var i = 0; i < init_physics.length; i++)    {        if (init_physics[i] == this.name)        {            log('Attemping initiation of physics for '+init_physics[i]);            // give other players physics            game.physics.arcade.enable(this.player);            this.player.body.reset(this.player.x, this.player.y);            init_physics.splice(i, 1);        }    }