# How to create custom 3D "areas" at runtime

I've been puzzled for a few days trying to solve this problem, so far with no results.

On a map, currently a Terrain, I'd need to have some "areas" which can be controlled by a specific players. The shape of those areas can arbitrarily change during the course of the game, such as you add a marker in any point, and the area evolves (like a spline, say) to pass through that point too.

The problem isn't drawing the boundary itself, of course, but having the GameObjects detecting the area they are in.

Currently I have absolutely zero idea on how to make this exactly.

I've thought about a nice approximation, which is splitting the terrain in fixed chunks, and having the player control them "chunk by chunk": every chunk can have its own collider, and that should be easy if not trivial. So the question is how to do it "properly", since I already have this workaround.

• I would create a polygon from the points, do a is-point-in-polygon check. Would that work for you? Jul 24, 2015 at 13:28
• @Felsir you mean, without using Unity components and functions like Colliders, instead having a custom-made function to do the check? That's brilliant and obvious, silly me! Could you post it as an answer, if that's really what you meant?
– o0'.
Jul 24, 2015 at 13:43
• That is exactly what I meant :-) Jul 24, 2015 at 14:05

I suggest this approach.

Use voronoi 2d subdivision for your space (in the example the central points distr is (pseudo)random, but you can insert your logic)

Then asociate a value to each point that results (in the example image) in different color for each cell

You can play with the number of point and/or distribution to get more defined shapes. For the voronoi diagram property, when you click on the map , the origin point nearest to your click position identifies the voronoi cell you are in.

• But isn't this basically equivalent to my workaround "divide it into chunks"?
– o0'.
Jul 24, 2015 at 14:03
• you overcome Unity colliders Jul 24, 2015 at 14:37

Create a polygon from the points, do a "is-point-in-polygon" check. So whenever the players add a point that would expand the "area" regenerate the polygon. On the update do a simple position check against that polygon to determine if an object or player is inside the area or not.

I solved this problem using an hybrid approach, inspired by:

• my original workaround
• @Felsir's post
• @dnkdrone.vs.drones's post

# Solution

I have Chunks, which may have an owner or be contested.

• Inside a contested Chunk, different players have their areas of influence.
• Instead of using a definite polygon/line border, inside the Chunk itself every player may place Flags.
• The Chunk itself is dividend into equally distanced ChunkPoints.
• A ChunkPoint's owner is the nearest Flag's owner.
• Chunk's % ownership is how many ChunkPoints you own.

# Sources

Using a polygon approach turned out to be too complex because I had to detect the order of the points, and they could with time take very complex shapes, which wasn't obvious how to handle.

I considered using voronoi's before realising that a ChunkPoint map was much easier and equally good for what I needed to do (but trying to use them was the source of inspiration that got me there).

In the original workaround idea, Chunks weren't "contested", they were just fully-owned by a single player, and that's why I didn't like them.