Convert mouse position to local position (relatively to the container

[no1no]

Hi, I'm a Phaser beginner and I'm trying to make a chess-like game. I created a background sprite with a board image. The first thing I want to do is getting the coordination of position on the board. I get it by pointing the mouse to each position and printing this.game.input.x,y in update() but it seems this is the world coordination and I can't use it to set the piece position (using chessPiece.position.set). Is there anyway to convert the world position to the local position?

[no1no]

My thread is at the end of page 1 after being approved so I hope no one mind a single bump to the top. *Bumped*

[drhayes]

Yes.

You're trying to map the game coordinates to your chess coordinates. It'll take some math. If you think about how your game is (for example) 800 pixels wide, and a chess board is 8 tiles wide, that means each tile is 800/8 === 100 pixels wide. So if the user clicks in pixel 234, that's 234/100 === 2nd tile.

[no1no]

Thanks. But that's not really what I want. I could calculate the position using math but I figure I would use the function of converting the world position to local position in the future so I was asking anyway. For example in a RTS game I could spawn an unit at the mouse position on the board. I tried

this.game.world.toLocal(new PIXI.Point(this.game.input.x, this.game.input.y), parentObject)

but it's incorrect.

[drhayes]

Phaser.Input similarly has getLocalPosition but I've never used it so I'm not sure what it does. The description sounds like what you're looking for?

But, truthfully, I don't understand what toLocal and toGlobal do, either. ( =

[lewster32]

Local position is just object position subtracted from world position, so if your world starts at 0, 0 and your object is at 100, 100, then if your cursor is at 150,150 (world position) then it's at 50,50 relative to the object. 

[no1no]

I see. Thank you for your answer, I can write a function base on it.

[in mono]

You may also want to take the sprite's anchor into account if you decide to use something different than (0, 0).