Collision detections with a background

[jmiller]

I don't want to detect collisions with other sprites, just with certain areas of the background. What's the best way to do this? I am not using any form of DX.
thanks in advance
jmiller

[Oafo]

Set up a coordinate array, and check to see if the coordinate is walkable. Something like this..

' get a few global variables in here
Private Map() As Long
Private MapW As Long
Private MapH As Long
 
Private Sub Form_Load()
    ' set the map width and height
    MapW& = 50
    MapH& = 50
    
    ' redim the Map array to fit the size of the map
    Redim Map(MapW& - 1, MapH& - 1) As Long
    
    ' make a few coords unwalkable
    Map(5, 5) = 1
    Map(5, 4) = 1
    Map(5, 3) = 1
End Sub
 
Private Sub MoveChar(X As Long, Y As Long)
    ' check to see if coord can be walked upon
    ' if not, then exit the movement function
    If Map(X, Y) = 1 Then Exit Sub
    
    ' character movement code here..
End Sub

If you need more help, post up.

[jmiller]

no that'll do nicely
thanks a lot
jmiller

[jmiller]

on second thought...
were you talking of actual pixels when you said 'coordinates'? i think what i want to do is use actual pixels, so movement is not confined to preset blocks of pixels. For simplicity, all the 'no-no spots' are going to be rectangles. would it be plausible to have rectangles of impassible areas for each map and then check all of them upon movement? The problem becomes a little more complicated when you consider that the users character is also a rectangle, and not just a pixel value. Speaking of that, how would one check for collision between two rectangles (I know how to check for a point and a rectangle)?
also, correct me if i'm wrong, but isn't there an api call for collision detection. i think i remember hearing of one once.
thanks
jmiller

[Sastraxi]

The API call is called IntersectRect, which asks for 2 RECT structs and returns 1, either 0,0,0,0 if no collision (I believe) or the area they collide in if they do collide. It's an invaluable API.

[jmiller]

i'm confused about the rect_api type. it goes:
Private Type RECT_API
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
going from the top-left corner of a rectangle clockwise, which variable applies to which corner?
thanks

[jmiller]

nevermind, i got it

[Oafo]

Left is exactly what it means in VB: the X position
Top is the same as in VB: the Y position
Right is: the X position + width
Bottom is: the Y position + height

Edit: too fast