error doing image collision detection with _MemGet

[SMcNeill]

Let me showcase a very simple collision detection routine that will work with all shapes and sizes of images:

Code: (Select All)

Dim As _Unsigned Long BSC, BJC, SJC, BSJC, CP 'bob+ sam collision, bob + joe collision, ect

$Console



Randomize Timer



Display = _NewImage(800, 600, 32)

Screen Display

_Console On

Bob = _NewImage(64, 64, 32)

Sam = _NewImage(64, 64, 32)

Joe = _NewImage(64, 64, 32)

Cls , _RGBA(255, 0, 0, 128), Bob

Cls , _RGBA(0, 255, 0, 128), Sam

Cls , _RGBA(0, 0, 255, 128), Joe



CollisionScreen = _NewImage(64, 64, 32)

_Source CollisionScreen 'to read the blended colors on that screen

_Dest CollisionScreen

_PutImage , Bob 'put bob on the screen

_PutImage , Sam 'put sam on the screen

BSC = Point(0, 0) 'we now know the blended color for a bob + sam collision

_PutImage , Joe 'put joe on the screen

BSJC = Point(0, 0) 'we now know the blended color for a bob + sam + joe collision

Cls , 0 'clear the screen we use for blending

_PutImage , Bob 'bob back on the screen

_PutImage , Joe 'joe on the screen

BJC = Point(0, 0) 'and now we know the blended color for bob + joe collison

Cls , 0 'clear the screen one last time

_PutImage , Sam 'put Sam on the screen

_PutImage , Joe 'put Joe on the screen

SJC = Point(0, 0) 'and now we know the blended color for a sam + joe collision

_Source Display 'restore the source to original screen

_Dest Display

_FreeImage CollisionScreen 'free that screen as we're done getting our blended colors



Dim As Long x(2), y(2)

For i = 0 To 2

    x(i) = Rnd * 700: y(i) = Rnd * 500 'random staring point of a character on the screen

Next

For i = 0 To 2

    Do Until xmove(i) <> 0: xmove(i) = Rnd * 10 - 5: Loop

    Do Until ymove(i) <> 0: ymove(i) = Rnd * 10 - 5: Loop

Next



Do

    Cls , 0 'clear the screen

    For i = 0 To 2 'generate movement

        If x(i) + xmove(i) >= 800 - 64 Then xmove(i) = -xmove(i)

        If x(i) + xmove(i) <= 0 Then xmove(i) = -xmove(i)

        If y(i) + ymove(i) >= 600 - 64 Then ymove(i) = -ymove(i)

        If y(i) + ymove(i) <= 0 Then ymove(i) = -ymove(i)

        x(i) = x(i) + xmove(i)

        y(i) = y(i) + ymove(i)

    Next

    _PutImage (x(0), y(0)), Bob

    _PutImage (x(1), y(1)), Sam

    _PutImage (x(2), y(2)), Joe



    'now do a quick collision detection check

    BSCE = 0: BSJCE = 0: SJCE = 0: BJCE = 0

    For x = 0 To 799: For y = 0 To 679 'detect collisions

            Select Case Point(x, y)

                Case BSC: BSCE = -1

                Case BSJC: BSJCE = -1

                Case SJC: SJCE = -1

                Case BJC: BJCE = -1

            End Select

    Next y, x

    If BSCE Then _Echo "Bob and Sam Collided!" 'report collisions

    If BSJCE Then _Echo "All three collided!"

    If SJCE Then _Echo "Sam and Joe Collided!"

    If BJCE Then _Echo "Bob and Joe Collided!"



    _Limit 120

    _Display

Loop Until _KeyHit

System

Now notice that I'm being lazy here and just making my "images" to be plain squares of 64x64 pixels (like a lot of sprites used in sprite sheets). This ***DOES NOT*** do square detection or rectangle detection or any real math at all. Like I mentioned on a different post about this, this is simply tossing paint at the wall and looking for colors that blend together.

Yellow + Blue = Green type logic.

Even using POINT, as you can see, this has no problems running and maintaining a nice fast animation speed for us. If you truly need, you can easily swap in a _MEM check here to speed it up even faster, but the overall process is really quite simple and efficient. Toss your images on a background screen (I'm doing all this on the main screen so you can watch it in real time as it happens), read that screen once and look for the existence of any collision colors.

Simple. Direct. Efficient. What's not to love about it, and no math is involved whatsoever!