This summer, I and my friends are planning to study geometry (this is the only topic, we know the least about).

But we don't know the topics required for ACM — ICPC and also don't have any source to refer to. I would like those of you who know better of this topic to please suggest some topics AND / OR material. This would help more guys like me to learn a new topic.

Any help regarding the same would be highly appreciated!!

I think this book would be helpful for you.

Siriuslight's comment above links to a nice book that gives the fundamentals for geometry in competitive programming.

There are plenty of problems that you could work on.

Here is a list of challenging geo problems from previous ACM ICPC World Finals (and some other contests).

Also, this page Timus has a large list of geometry problems from other contests that are supposed to be high quality.

Here(https://www.quora.com/How-should-I-prepare-for-geometry-for-ACM-ICPC-1) is a response by Zobayer Hasan, giving an overview of ICPC geo and sources to more problems.

Chapter 7 here has sample code that you can use for polygons, lines, triangles, circles, etc...

I personally am weak in geometry too (I have some survival Euclidean geo experience from math contests but I am yet to look into computational geo problems, which seems to be what ICPC largely consists of).