weightedPick() looks biased

[samme]

Version

• Phaser Version: 3.0.0 to 3.60.0

Description

shy and wayfinder reported/tested this on Discord.

It looks like weightedPick() undersamples the first and last array members.

Example Test Code

https://codepen.io/samme/pen/qBQKYxN?editors=0110

Additional Information

I think it's supposed to be

return array[~~(Math.pow(this.frac(), 2) * array.length)];

[photonstorm]

Thanks. I think the distribution looks better with return array[~~(Math.pow(this.frac(), 2) * array.length + 0.5)];:

As without the 0.5, the first element is massively favoured:

But it definitely looks wrong with the array.length - 1.