error doing image collision detection with _MemGet

[bplus]

@bplus you need to update these routines for the newest versions of QB64PE.

Code: (Select All)

Function BoxCollision% (b1x, b1y, b1w, b1h, b2x, b2y, b2w, b2h)

    ' x, y represent the box left most x and top most y

    ' w, h represent the box width and height which is the usual way sprites / tiles / images are described

    ' such that boxbottom = by + bh

    '        and boxright = bx + bw



    If (b1y + b1h < b2y) Or (b1y > b2y + b2h) Or (b1x > b2x + b2w) Or (b1x + b1w < b2x) Then

        BoxCollision% = 0

    Else

        BoxCollision% = -1

    End If

End Function\

Change all those OR statements to _ORELSE statements.  A collision routine like this is one place where ORELSE could prove to make a heckuva change in performance.

OR is a mathematical process.  It involves doing math on bits and the above will take  3 different math processes to arrive at an answer.

_ORELSE does a binary TRUE/FALSE compare -- **WITH** break logic installed built in it.

IF a = b OR a = c OR a = d THEN  ....  This will solve it as (a = b)  then do the (a = c) then do the (a = d).  Then it'll OR the first two values.  Then OR the result of that and the last value to get a final result.  Multiple processes here.

IF a = b _ORELSE a = c _ORELSE a = d THEN....  This will solve (a=b).  If the result is 0, it's done.  No need to do anything more. 

This statement:

IF a = b _ORELSE a = c _ORELSE a = d THEN

Would translate closer to this code:

IF a = b THEN
  IF a = c THEN
      IF a = d THEN


The first time it fails to produce a positive result, it's done.  No need to do the other parts.

See where that might make quite an improvement for a collision routine, which is being called X number of times per loop?

I dont think I actually use that SUB, I like the one that provides the info of where the intersect point, line or box exists exactly.

But thankyou for explaining the advantage of the new _OrElse, that is handy to know and even to be reminded of for this old dog.