Alright. A friend on BW just told me about mobile gridding for moving locations around a specific target, and i've got that down.

What Im Doing : Making an arena map, no specific theme ( 3v3 )
what I need help with : Im making a specific spell/trigger.

You have a hydralisk in the middle. Locations To the sides, above, and below it.
Say you move the hydralisk to the right.
What would the process of triggers be to...Make a line of seige tanks to the right? One after another, not all at once.

This is my first thread on this sight, so thank you in advanced. You can reach me faster by skype : bsgunner

Mobile grids would be your best bet if you want the tanks to be placed relative to the hydralisk.

When the hydralisk moves right, it triggers the siege tanks to be created to the right of it? I'm a little unclear on that part. Also, how much of a delay do you want between siege tanks?

Without knowing those things, I can still give you a general answer. The way you create a line of siege tanks is by having a location center on the siege tank you just created, and then perform the same mobile grid trigger from there, to create another siege tank to the right of it. Center the location on this new siege tank, and repeat the process until you have as many siege tanks as you're hoping for.

If there's a possibility of misplace errors, keep in mind that you can create each siege tank at some empty spot outside the arena, and then move it to the location where it's supposed to appear (instead of just creating it at the location). This prevents the possibility of misplace errors, since "move unit" doesn't cause them. Just make sure your "create unit" trigger only fires when there's no siege tanks in the creation location

When the hydralisk moves to the right, I need to know how to make seige tanks start to spawn, from the hydralisk at first, and then moving away.
I would not like them to spawn instantly, but maybe on a 1 second, 1.5 second timer inbetween?
Mobile gridding for this would be sloppy.
A friend told me it would be direction detection, but I have no idea what that is.

I edited in a bit more information for you in the previous post

You'll want to use death counters along with hyper triggers (which you're hopefully using already) to achieve the delay effect. For 1 second, you'll want to use 12 DCs, and for 1.5 seconds you'd use 18 DCs.

12 death counters = 1 second? Never knew that. Thanks! That'll come in handy.

11.9 DCs per real-time second when playing at Fastest. At slower speeds, there are fewer. The 11.9 vs 12 distinction doesn't matter, unless you're dealing with sounds files 10s or longer.

There's a pure trigger direction detection method I came up with.

Or you can use a far simpler EUD method.

starcraft runs at 15 frames per normal second, 16 frames per game second, 24 frames per fastest second. hyper triggers run every other frame. Thus half of that is 12 hyper triggers per second. It's not 100% accurate so for long durations you'll want to calculate/test it out. I think it's something like 23.810 fps.

Here's direction detection:
http://www.staredit.net/files/422/
http://www.staredit.net/files/2860/

It really just calculates the slope using buried zerglings though.

If you've only got 4 directions you want the tanks to go in, then mobile grids is the way to go. If you've got more than 8 directions, then direction detection is the way to go. For the mobile grid part, I wouldn't center on the tank, but rather on the devourer used in the mobile grid. One tank unplaceable means the tanks will stop spawning until the object moves out of the way.

The key to the speeds is that at Fastest, 1 hyper-trigger cycle (often referred to in terms of 'DCs' - death counts) happens exactly every 84 milliseconds. 1000 / 84 = 11.905.. hyper-trigger cycles per second. Since it's every 2nd frame, Fastest runs at 23.81... frames per second.