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I'm experimenting with collisions in DB Classic but can't get my program to detect when two objects touch each other unless I use Global Collisions.
I'm using this short program to test collisions:

load object "topball.3ds", 1
load object "topball.3ds", 15

position object 1, 0, -100, 0
set object collision on 1
set object collision on 15
set object collision to spheres 1
set object collision to spheres 15

a = 50

do

position object 15, 0, a, 0
if upkey() = 1 then a = a + 1
if downkey() = 1 then a = a - 1
if object collision(1, 15) = 1 then end

loop

I don't want to use Global Collision because in my real program there are many more objects on the screen and the game literally stops running. Can anyone tell me what I'm doing wrong here?

Thanks!!!

After a few hrs break from my original message I turned my computer back on and tried the same program with no changes at all and it worked. The collision was detected.
I thought the problem was gone however when I tried to use the same test program within my real program (as a separate loop at the beginning of the program) I didn't work anymore.
If anyone can offer any advise I'll really appreciate it.
Thanks!