Math Help

[marsh]

Hello, i am having some problems. Hopefully i can explain it to you without getting you to confused.

Basically i have a 2D game which has a total of 300 tiles in a 20 x 15 grid. Each tile is 32 pixels. I am trying to find the player position in one number. His x position is indicated by a variable called x likewise with this y position. But that is the total pixel position. So to get his actual tile number you need to divide by 32.

So to find out his total position i basically need to get his x number. Then times it by 20 (the number of tiles on the line) for every row of y he is down. I have a formula that sort of works. The problem is that when i walk halfway down a tile going in the y direction it starts adding numbers to my total tile. I only want it to calculate when i have moved a entire 32 pixels.

Here is my formula.

playertile = ((y / 32) * 20 + 20) + ((x / 32)) - 20;

I am aware it may be completely wrong as i suck at math. Even so this basically gets the right tile number if i am perfectly down 32 pixels. The problem is if im only down half a tile say 15 pixels it will still add some numbers.

(+ 32 is becouse i want the first tile to be 1 and not 0)
x + 32) / 32 gets the perfect x position
x + 32) / 32 gets the perfect y position

so how do i get my total position? i also tried : y + 32 / 32 * 20 + x + 32 / 32 but it was the same problem of moving halfway down a tile. I guess i need it to round to the nearest 32, whatever tile its closer to or something.



If you are still confused basically i want the Y below to return 26. Or the b would return 300.

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Anyone no how i may go about this? Thanks. I know its confusing hopefully i explained it well enough for you to understand. Thanks for any help i receive .

[alanjhd08]

Hi,

As long as you use integer arithmetic, looks like that should work. Have you declared playertile, x & y as int?

Alan

[GCDEF]

If I'm following you, let's assume the values for for your position y are x = 200 and y = 50.

Step 1 is finding the row number. You can do that with y / 32, which is 1 in this case. Multiply that by 20. That gives you
(y / 32) * 20.

Then you need to find the column number, which is x / 32, in this case 6. Add that to the previous result and you get

((y / 32) * 20) + (x / 32).

Plugging in the numbers, you get
((50 / 32) * 20) + (200 / 32).
(1 * 20) + (6)
20 + 6
26

[alanjhd08]

Hi marsh,

Since
playertile = ((y / 32) * 20) + (x / 32);
is basically the same as:
playertile = ((y / 32) * 20 + 20) + ((x / 32)) - 20;

as GCDEF points out, it should work correctly.

Alan

[marsh]

Hi,

As long as you use integer arithmetic, looks like that should work. Have you declared playertile, x & y as int?

Alan

Sorry for wasting your guys time. I changed x and y to a float for some other calculations. So this must have broke the formula with the decimals. It works now thank you all very much.