Creating X and Y axis for a game

Question

Recently I was thinking about creating my own axis x/y, especially 'x', but in that game in which I want to create it, there are no values below 0, because pointX = 0 is on left screen border.

I want to create function which will smoothly count all values depends on our game resolution X.

For example:

parameters: min value, max value, screenX, cursorPosition

if(cursorPosition == screenWidth/2) then
  return 0
end

When cursor position is below screenWidth/2, function will smoothly count value between -0 and min value (min value will be, when cursor position = 0)

and the same when cursor pos is above screenWidth/2, function will smoothly count value between 0 and max value (max value will be when cursor position = our screenX)

Can anyone explain to me, how can I reach an effect like that? :)

Regards

Answer 1

use linear interpolation to change the dynamic range. Let assume your view has xs,ys resolution and point (0,0) is top left corner. so the dynamic range per each axis is:

x = <0,xs-1>
y = <0,ys-1>

and you want to change it to:

x' = <minx,maxx>
y' = <miny,maxy>

So do this:

x' = minx + x*(maxx-minx)/(xs-1)
y' = miny + y*(maxy-miny)/(ys-1)

and if you need to go back for any reason:

x = (x'-minx)*(xs-1)/(maxx-minx)
y = (y'-miny)*(ys-1)/(maxy-miny)

where (minx,miny) is top left corner and (maxx,maxy) is bottom right corner. If you want to change also the sign of any axis then you can as minx<maxx is not required for this so just swap the initial values so minx>maxx.

Not coding in lua but If your values are floating then beware integer rounding while mixing integers and floats together.