'Compare to one of the alterable values' VS 'Compare two general values'

[King_Cool]

Say i have 10 instances of ObjectA, does it matter which one i use ( topic )? Will both methods select instances seperatly?

[LB]

Only conditions which come from the object in question will select objects, with a few exceptions. Compare two general values will never modify the selection. Events such as collisions will select both objects. All objects involved in the condition are selected at the same time, and actions performed on those objects are run on a per-object basis. Does this help?

[MuddyMole]

Yes, it very definitely DOES matter which you use!
You almost never want to use "Compare two general values" when working with multiple instances.

Suppose we want to have lots of Enemy objects, which will shoot at the Player when they are within 100 pixels.

+ Compare two general values: Sqr(((X("Enemy") - X("Player")) pow 2) + ((Y("Enemy") - Y("Player")) pow 2)) < 100
-> Enemy: Shoot at Player

This will NOT work. What will happen is that MMF2 will calculate the distance between the Player and the newest Enemy instance - and if it's less than 100 pixels, it will make ALL enemies shoot at the Player.


+ Always
-> Enemy: Set Distance to: Sqr(((X("Enemy") - X("Player")) pow 2) + ((Y("Enemy") - Y("Player")) pow 2))

+ Enemy: Distance < 100
-> Enemy: Shoot at Player

This WILL work. It calculates the distance for each individual Enemy, and then compares them separately to 100.
9 times out of 10, when people resort to spread values & fastloops or ForEach loops, there's no need - they could have just used an extra alterable value instead.

Read these:
http://www.create-games.com/article.asp?id=1975
http://www.create-games.com/article.asp?id=2248