UGTK / Toolkit / Utility Systems / Collision System Completed

Collision System

Summary

The Collision System brings Unity's collision, trigger and pointer callbacks into the inspector. Instead of writing a script with OnTriggerEnter for every object that has to react, you drop a component and wire the reaction as a UnityEvent — the same way you wire a Button.

It covers three families: 3D physics, 2D physics, and pointer interaction (mouse or touch) on an object.

Modules Dependencies

None. Four independent components that only use UnityEngine and UnityEngine.EventSystems.

Setup

3D physics — drop the collider prefab that matches the shape you need:

2D physics — the 2DColliderObject prefab:

Pointer interaction — ColliderMouse for the cursor, ColliderTouch for the finger:

Then wire the reactions in the inspector, like any UnityEvent:

How To Use

Mn_Collider3DEvents / Mn_Collider2DEvents expose the six physics callbacks:

Event	Raised
`onCollisionEnter` / `onCollisionEnter2D`	when the collision begins, with the collision data
`onCollisionStay` / `onCollisionStay2D`	every physics step while it lasts
`onCollisionExit` / `onCollisionExit2D`	when it ends
`onTriggerEnter` / `onTriggerEnter2D`	when something enters the trigger, with the other collider
`onTriggerStay` / `onTriggerStay2D`	every physics step while it is inside
`onTriggerExit` / `onTriggerExit2D`	when it leaves

SetInteraction(false) silences the whole set without touching the collider: physics keeps behaving identically — the object still blocks, still pushes — only the reactions stop. That is the difference from disabling the collider, and it is usually what you want during a cutscene or a death animation.

Mn_ColliderMouse / Mn_ColliderTouch expose enter, over, exit, down, up and hold. The Hold event is the one Unity does not give you: it fires every frame while the press lasts, which is what a charge-up or a long-press needs.

Good to know:

Stay events fire every physics step, up to 50 times a second per contact. Anything heavier than a flag flip belongs in Enter.
onMouseUp / onTouchUp fire on release anywhere, not only over the object: the press started here, so this component gets the release. For "released on the object", check the pointer is still inside.
The two pointer components are near-identical: on a touch device the EventSystem reports touches through the same pointer callbacks, so ColliderMouse also responds to a finger. Use ColliderTouch for intent, not because the other one would not work.

What Unity Requires Anyway

This module wires the callbacks, it does not remove Unity's own requirements. Almost every "it does not fire" comes from one of these:

Physics events need a Rigidbody. Two static colliders never generate any callback: at least one of the two objects needs a Rigidbody (or Rigidbody2D), even a kinematic one.
Trigger events need Is Trigger on one of the colliders — and a trigger does not raise collision events, only trigger ones.
The layers must collide in the Physics collision matrix.
Pointer events need an EventSystem in the scene and a raycaster that can see the object: a Graphic Raycaster on the canvas for UI, a Physics Raycaster (or Physics 2D Raycaster) on the camera for colliders. Without the raycaster nothing is raised and nothing warns you.
2D and 3D do not mix: a Collider2D never talks to a Collider, and the two components are not interchangeable.

Testing Scene

Open Debug/CollisionScene.unity and press Play: the objects collide and CollisionCallbackExample logs every event it receives, so you can see which ones actually fire.

Technical Info

Path	Content
`Scripts/Mn_Collider3DEvents.cs`	The six 3D physics events plus `SetInteraction`
`Scripts/2DCollision/Mn_Collider2DEvents.cs`	The six 2D physics events plus `SetInteraction`
`Scripts/2DCollision/Mn_ColliderMouse.cs`	Mouse enter/over/exit/down/up/hold through the EventSystem
`Scripts/2DCollision/Mn_ColliderTouch.cs`	The same for touch
`Prefabs/3DColliders/*.prefab`	Box, Sphere and Capsule ready to use
`Prefabs/2D/*.prefab`	2D collider, mouse and touch
`Debug/CollisionCallbackExample.cs`, `Debug/CollisionScene.unity`	Sample listener and test scene