The game has cars and collisions, and I'm trying to create the following system:
- When a car T-bones another, the one getting T-boned is destroyed;
- When the cars collide laterally (usually just bump into each other), a normal physics collision happens (and nothing is destroyed);
- When the cars collide head-on, the lighter one is destroyed.
The cars are all instantiated from 1 prefab. This can't be changed.
The main body sans the bumper has a normal, non-trigger collider and the dynamic Rigidbody. It has the tag "Destructible".
A child object (which also houses the bumper model, but that shouldn't matter) has a normal, non-trigger collider for the bumper. It has no Rigidbody and reports to the parent's Rigidbody. It has the tag "Destroyer".
transform.forwards of both cars and compute their dot product.
- If the 2 vectors are opposite each other (or close to it), destroy the lighter car.
- If the vectors are facing away from each other (or are close to parallel), let a normal collision happen.
- If the vectors are perpendicular (or somewhere in that ballpark)... then I'm lost. How do I know which car T-boned which?
That brings us to the solution #2.
2) The 'multiple colliders' solution
Assign another collider to the bumper of the car and give it a separate tag (e.g. "Destroyer). As a consequence, give the other — main — collider a tag, too (e.g. "Destructible").
- If a Destroyer collider hits a Destructible, the latter is destroyed.
- If a Destructible hits a Destructible, a normal physics collision happens.
- If a Destroyer hits a Destroyer, destroy the lighter one.
But here, I run into an issue.
- You can't have multiple colliders on the same game object. Ergo, create an empty child and attach it there. I won't set it to Trigger, or otherwise it won't detect collisions with another of its type (i.e. Destroyer).
- In order to destroy colliding objects, I need a script and an
OnCollisionEnter()won't run if neither of the game objects has a non-kinematic Rigidbody. This means I need to give the bumper colliders a non-kinematic Rigidbody.
- But if I give them dynamic Rigidbodies, they'll just... float away from the car.
In other words, I need a way to create a 2nd collider but keep it firmly attached to the car. Furthermore, if the main collider covers it, then I need to exempt it from collisions with the 2nd collider (let's call it the sub-collider), and I can't use layers to do that or otherwise the sub-collider won't detect main colliders on other cars.
If I don't cover it, then I need the sub-collider to act as a normal physics collider, too, when it hits, for example, a wall, and not have the bumper sink into it. That means it needs a non-kinematic Rigidbody.
How can I solve this issue?