You may do what you need in 2 step:

1. Clustering: First you can cluster your point. There are many clustering algorithms which will put your points into multiple close-distance group.

2. Convex Hull: Then you can create Convex Hull for each cluster.

You can find many algorithms for both easily by dear Google in your desired programming language.

You may do what you need in 2 step:

1. Clustering: First you can cluster your point. There are many clustering algorithms which will put your points into multiple close-distance group. K-means is one of your options.

2. Convex Hull: Then you can create Convex Hull for each cluster. such as: Gift wrapping algorithm, Quick Hull, Bridge, ...

There is a trade-off between simplicity and performance issue for named algorithms.

As you run these algorithms in real-time, your case go to performance-intensive category which need some research in order to find best algorithms for your game.