Mathematical Genius Required

[badkarma]

Hello there,

I am making an "old school text based game" where you move a character around the screen. I dont really want to use the device's hardware keys but instead to use the stylus on the screen and where you click on the screen determines where your "character" moves in the maze (North, East, South, West) (imagine Pacman type game).

My dilemma is, does anyone know of a smart piece of code or function which will return a "N" or "E" or "W" or "S" depending where they click on the screen (using for example Form1.MouseDown(X,Y)?

An example "320x200" area screen and clickable "trinagled area" points and return values can be seen in the attached click.GIF.

Does anyone know a calculable formula for translating X,Y of the four areas highlighted into the N E W S returns for my app?

Thank you.

[LineCutter]

Assuming that you know where the middle of the screen (Form.height/2 etc) is then you know the 45 degree lines run at x=y, x=-y, y=-x & -y=-x.

So if (screentap x value) minus (screen centre x value) is positive but > than the absolute value of y then the move is east. Ror x being negative the move is west. After that, if (Screen tap y) - (Screen centre y) is positive then the move is north (You've already excluded it being E or W) & a negative value is south.
Note that taps on the lines go N or S (You could change the default, or simply view this as a way to irritate indecisive players).

The coding (if then statements nested) should be straight forward, although you might want to read the help file for Abs().

[Upquark]

I think that only applies when the screen is a square. Following badkarma's example, you'll have to deal with the slopes of the lines (i.e. y=(200/320)*x etc.) which makes it slightly less straightforward.

My approach would be to consider the 2 diagonals:
- Diagonal 1: y = (height/width) * x
- Diagonal 2: y = height - ((height/width) * x)

And check whether the clicked position is:
- Above diagonal 1 and 2 => North
- Above diagonal 1 and below diagonal 2 => West
etc.

[agraham]

I think this does it although I haven't run it so it could well fail. Assuming the detection rectangle has co-ordinates (XL,YL), (XR,YR)

mousex = mousex - XL
mousey = mousey - YL
X = XR - XL 
Y = YR - YL 
pos = 0
if mousey > mousex*Y/X then
 pos = 1 ' 0 is S or W, 1 is N or E
if mousex > (Y - mousey)*X/Y then
  pos = pos + 2 ' 0 is N or W, 2 is S or E
...
' pos 0 = W, 1 = N, 2 = S, 3 = E

[badkarma]

Thank you all for your time taken for your replies, hints and tips, and formulas, I really do appreciate it.

I now have it working and have put the example here...

Detecting Zone tap regions North East West South

Once again, many thanks for your time, I'm not the best with formulas for maths

Cheers

Steve