So my area of battle has three regions: In which the outside has the weakest to the strongest to the center. However, it is common logic that the outermost region(weakest) will spawn any unit all over the map which means the regions inside are also included. I want that the weakest only spawn outside without spawning in the inner regions. I lack understanding in regions yet, especially triggers regarding regions so I want to ask here thanks
Simplest approach is to test if the random position is within the inner region (JASS/Lua Rect) and if so then generate another random position. As long as the inner regions are reasonably small compared to the outer spawn region, this should be pretty reliable. Even still I would recommend giving up after 20 or so tries and instead spawning in some default known proper but not random location. The fail condition should happen so infrequently that players would likely not notice.
The more complex approach is to break the outer region into multiple, non-overlapping, smaller regions that exclude the inner region. A region to spawn in is then chosen randomly based on the weight of their area, and then the position is selected randomly as normal. This is the most performant and reliable way to spawn a unit randomly under these conditions, but the logic to fragment the outer region is much more complex.
Additional: How to make circular regions? (if impossible, how to make multiple regions that can be treated as only one region (region 1,2,3 as only one region - like in spawning units))
Rect, as their name might indicate, are
rectangular. Actual JASS/Lua regions seem to be a collection of map cells, so could represent a discretely sampled circle area. Actual regions do not natively support getting a random position within them, you would need to resort to the first described logic of itterative tries of points within a bounding box.
If you want to spawn units in a circular area then you can write your own logic to do so. Specifically you select a random angle and radius, and then correct the radius to compensate for the distortion of the radius/angle axis. This distortion compensation is fairly trivial to implement, something like
R * sqrt(random(0.0, 1.0))), but is required for uniform probability distribution, otherwise points will bias towards the middle of the circle.
StarCraft II added native support to circular, and composite, regions, including logic shapes to remove areas from regions. The random point logic they used is the same as I described originally, they generate a random point in the bounds of the composite shape and then check if it is inside the region, repeating until either the point passes or a try limit is reached causing a null value to be returned.
