Access control where a user can belong to multiple groups with multiple permissions?

For example we have:

User1, User2, User3

Group1, Group2, Group3

Permission1, Permission2, Permission3

User1 belongs to Group1 where it can do Permission1, and Group2 where it can do Permission2 and Permission3, etc.

Is there a simple UI pattern for this? Is it still necessary (wasn't planning on it) to assign the permissions to roles then users to those roles even for this simple use case?