LibGDX obstacle collision

Question

How can I handle collisions with obstacles in LibGDX?

Is there any automatic way to stop the character's movement when it collides with a wall or I have to constantly poll for all the possible objects it might encounter and stop the movement accordingly? Polling this way seems pretty poor performance-wise, especially if the framework already does that for me and I make no use of it.

My game is a top view roguelike, more or less like "The Binding of Isaac".

EDIT some beginners like me might make good use of it. Since LibGDX has no built in collision detection without Box2D, for games where physic calculation is not needed you can build your system as follows: Create 3 lists (Static, Dynamic, Controlled) where you put all your (relatively inherited) objects in the scene.

Static objects (walls, obstacles, traps) are passive and perform no checks.

Dynamic objects (projectiles) perform checks on both Static (stop if you hit a wall, destroy self) and Controlled (deal damage)

Controlled (players, enemies) objects perform checks on self (player hit AI controlled enemy) and static objects

After a collision is reported notify the relative objects. Controlled objects can be Dynamic aswell but if you have a lot of projectiles flying around you can avoid self-checking Dynamics and improve the performance. This way you should reduce a lot of useless checks aswell as limit cross-checks (both player and projectile notifying eachother) and keep your game well organized. This is just an idea that i'm testing now, I can't guarantee it's the best :P

Answer 1

Libgdx does not handle this itself, you need to take care about collision detection + collision response yourself.
One possible solution would be Box2D, a 2D physic engine. It takes care about forces, mass, friction and other physical things. It also detects and handles collisions for you. It is also possible to let Box2D just detect the collision and notify you about it, so that you can use a custom collision response.
As you allready said in the comments, Box2D would be overkill in your case, as you don't need physics, but only collision detection + response.

That means, that you need to implement collision detection + response yourself. Libgdx has some usefull methods inside the Intersector class. There are methods, which tell you, if two Shapes (for example 2 Rectangles) overlap. Others return the intersection-shape, which might be interesting for the collision response.

As said in the comments you can use Scene2D, where you are working with so called Actors which take part of a Stage. They have a position and a size you can use for collision detection. Unfortunately in Scene2D the act (logical-part / Model) as well as the draw method (visual-part / View) are in the same class (Actor), which makes it hard, if not impossible, to implement a MVC-Pattern. This might be ok for UI and simple games, but it could cause problems for bigger, more complex, projects.
So you might want to implement your own "game-world" and "game-objects", but thats up to you.

As you allready said, you can "poll" for every possible collision, which might work for small worlds if there are only a few objects. If there are to many objects, you can use different things to reduce the amount of complex checks:

• Use filters, if for example Player can't collide with other Players, you don't even need to check, if they are colliding or not
• Use AABB check, before starting to check for the real collision. This will allready sort out most of the objects with a verry simple check, before performing a more complicated check
• There are also things like Quadtrees, but i guess that would be overkill in your case.

I hope it helps.