Initialization of BoxImpostor and CannonJSPlugin

Bugs
1

Moving meshes (e.g. mesh.position.y = 3) AFTER creating a BoxImpostor during initialization phase (means before first physics update cycle) causes a big initial velocity.

This is only the case with the CannonJSPlugin.

const SHOW_BUG = true;
var box = BABYLON.MeshBuilder.CreateBox("box", {}, scene);
if (!SHOW_BUG) { box.position.y = 3; }
var impostor = new BABYLON.PhysicsImpostor( box, BABYLON.PhysicsImpostor.BoxImpostor, { mass: 1}, scene);
if (SHOW_BUG) { box.position.y = 3; }

https://playground.babylonjs.com/#6HFBC4#1

2

just like computeWorldMatrix that sometimes needs to be forced, if you change the position in a single frame after initializing you can force an update which prevents this issue - https://playground.babylonjs.com/#6HFBC4#2 .

I agree that it is not optimal, you can add an issue on github (you can assign me), but in the meantime I will recommend forcing the impostor update or setting the position prior to creating the impostor

3

Hi Raanan!

Thx for the quick response. I filed an issue on github but (as it seems) Iā€™m not allowed to assign it to anybody.

Yes, my report already hints the countermeasure you suggest, it just took me half a day to find out and I ran across issues of other people with the same root cause (like this https://www.babylonjs-playground.com/#1RKZXB#6 , which also can easily be fixed by moving the positioning code). So it is at least confusing.

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