Mouse over Tiles - GameCreators Forum

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fllwthewolves

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Posted: 1st Jan 2012 21:58

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so im trying to write a game which requires me to create a series of tiles over the screen and then figure out which tile the mouse is over. to create the tiles i used this

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 for x = 1 to 30
        for y =1 to 30
            `places the values in the array
            grid(c).left = (woftile*x)-woftile
            grid(c).top = (hoftile*y)-hoftile
            grid(c).right = (woftile*x)-1
            grid(c).bottom = (hoftile*y)-1
            grid(c).number = c
        `next slot
            inc c
        
        
        next y
    next x

i used a array defined as a type to measure out the coordinates of the grid. my problem is that i cant figure out a way to figure out which tile the mouse is over... any ideas?

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Chris Tate

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Location: London, England

Posted: 1st Jan 2012 22:18 Edited at: 1st Jan 2012 22:32

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Hi

There are two commands which reveal the location of the mouse cursor within the DBPRO window.

MouseX() & MouseY()

So you can check which grid tile overlaps the mouse using an expression:

+ Code Snippet

If MouseX() => Grid(c).Left And MouseY() => Grid(c).Top And MouseX() < Grid(c).Right And MouseY() < Grid(c).Bottom Then TileUnderMouse = c

There are other ways to solve the problem but this is the easiest way I can think of.

+ Code Snippet

c = 1
For x = 1 to 30
   For y =1 to 30
      If MouseX() => Grid(c).Left And MouseY() => Grid(c).Top And MouseX() < Grid(c).Right And MouseY() < Grid(c).Bottom Then TileUnderMouse = c
      Inc c
   Next y
Next x

You could also calculate the tile mathematically using the following:
x = Floor( MouseX() / woftile ) + 1
y = Floor( MouseY() / hoftile ) + 1
TileUnderMouse = x + ( ( y - 1 ) * 30 )

The calculation process will run faster but is more difficult to read. I've assumed your array index starts at 1. If not, deduct 1 from TileUnderMouse in the last line of the calculation example.

Edit: Note that if the mouse position is out of tile range, the wrong tile will be returned; so in both examples, you should check that the mouse is within the grid; if it is not then set the TileUnderMouse as zero, to indicate that there is no tile under the mouse.

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fllwthewolves

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Posted: 1st Jan 2012 22:29

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if i put that inside my main loop wont it kill my speed?

either way thanks so far its working great.

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Chris Tate

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Posted: 1st Jan 2012 22:39

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Quote: "x = Floor( MouseX() / woftile ) + 1
y = Floor( MouseY() / hoftile ) + 1
TileUnderMouse = x + ( ( y - 1 ) * 30 )"

Using the calculation method will work faster than the for loop; but if you have to update each tile anyway, there is no difference; you are already iterating through them so you may as well use any existing for loop for this and similar expressions.

Quote: "Edit: Note that if the mouse position is out of tile range, the wrong tile will be returned; so in both examples, you should check that the mouse is within the grid; if it is not then set the TileUnderMouse as zero, to indicate that there is no tile under the mouse."

Most of todays computers will update 100s of tiles pretty swiftly anyway; it falls down to how much is going on during your game.

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LBFN

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Location: USA

Posted: 2nd Jan 2012 01:52

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While I love using TYPE variables, this is one case where I would use a two-dimensional array (i.e. dim grid(30,30) ) instead.

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TileX = int(mousex() / TileWidth) 
TileY = int(mousey() / TileHeight)
if TileX < 1 then TileX = 1
if TileX > 30 then TileX = 30
if TileY < 1 then TileY = 1
if TileY > 30 then TileY = 30
if grid(TileX,TileY) > 0 then [do something]

This code assumes that you set the TileWidth and TileHeight variables. I would not cycle through all 900 possibilities, as that would slow it down a lot.

So many games to code.......so little time.

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Agent

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Location: Sydney, Australia

Posted: 2nd Jan 2012 06:33

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I use the mathematical solution, myself. You won't find that calculations such as this slow your cycle speed by a noticeable amount unless you are misusing it by putting it inside redundant loops.

I suggest you don't place this code inside your mainloop - make a function of it that returns the tile in question. That way you only need to call the code once at a time, such as when you click. At the very least, only call code like this when you intend to use the result immediately. There's no need to calculate the tile position every mainloop cycle unless you are going to use it every single cycle.

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