As mentioned previously, we can treat our physics objects as normal colliders or as trigger volumes. An important distinction between these two types is that the OnCollider...() callbacks provide a Collision object as a parameter to the callback, which contains useful information such as the exact location of collision (helpful to position a particle effect) and the contact normal (useful if we want to move the object after the collision manually). However, the OnTrigger...() callbacks do not provide this kind of information.

As a result, we should not try to use trigger volumes for collision-reactive behavior since we won't have enough information to make the collision appear accurate. trigger volumes are best used for their intended purpose of tracking when an object enters/exits a specific area, such as dealing with damage while a player stays in a lava pit, triggering a cutscene when a player enters a building, and initiating asynchronous loading/unloading of a scene when the player approaches/moves far enough away from another major area.

If the contact information is absolutely needed for a trigger volume collision, then common workarounds are to do any of the following:

• Generate a rough estimate for the contact point by halving the distance between the trigger volume and colliding objects' centers of mass (this assumes that they're of roughly equal size).
• Perform a raycast upon collision from the center of the trigger volume to the center of mass of the colliding object (works best if both of the objects are spherical).
• Create a non-trigger volume object, give it an infinitesimally small mass (so that its presence barely affects the colliding object), and immediately destroy it upon collision (since a collision with such a large mass differential will probably send this small object into orbit).

Of course, each of these approaches has its drawbacks—limited physical accuracy, extra CPU overhead during the collision, and/or additional scene setup (and rather hacky-looking collision code)—but they can be useful in a pinch.