Question by Mulberg · Nov 20, 2019 at 06:13 AM · physics2d collision detection raycasthit2d

Custom collision between 2 moving objects

Hello everyone!

First time asker here =)

I'm making an Arkanoid game clone, and have troubles with resolving collisions between the paddle and the ball.

I decided to use custom collision detection using Physics2D.CircleCast and movement with transform.Translate instead of using RigidBody. This allows me to control the ball's movement with more precision, do trajectory corrections, and so on. I'm happy with the result overall: the ball bounces of the static obstacles without falling into collides even on a very high speed.

However, when it comes to bouncing of the paddle there are some problems. Here is a very simplified version of my code:

 Vector2 movementAmount = direction * _currentSpeed * Time.deltaTime;
 RaycastHit2D hit = Physics2D.CircleCast( ...) 
 
 if (hit.collider != null) {
   // correct move amount
   // calculate `nextDirection`
 }    
 
 transform.Translate(movementAmount, Space.World);
 direction = nextDirection;

The problem is, when the ball and the paddle move towards each other, there might be a frame or two when the CircleCast "misses" the paddle, because these 2 objects are not moved synchronously.

What I need, is somewhat "predict" a collision that should happen.

Overall, I'm kinda overwhelmed. I like this idea of using a custom raycast controllers (like in Sebastian Lague's tutorial), but don't understand in general how to deal with interactions of 2 or more moving objects (without using a built-in Physics).

Thanks.

Collision