How do I make GameObjects use physics to interact with each other using Vuforia?

Question

I'm using Vuforia for an AR school project and am trying to make a Roll a Ball game. However, the ball keeps falling through the ground despite the fact that both the ground and the ball have colliders. How can I the ball interact with the ground?

Answer 1

In general you always need at least one Rigidbody in order to get collisions via the physics engine.

A Rigidbody is the main component that enables physical behaviour for a GameObject

What you would probably use for that is a kinematic Rigidbody on your moved object.

This is a GameObject with a Collider and a kinematic Rigidbody attached (ie, the IsKinematic property of the Rigidbody is enabled). You can move a kinematic rigidbody object from a script by modifying its Transform Component but it will not respond to collisions and forces like a non-kinematic rigidbody. Kinematic rigidbodies should be used for colliders that can be moved or disabled/enabled occasionally but that should otherwise behave like static colliders. An example of this is a sliding door that should normally act as an immovable physical obstacle but can be opened when necessary. Unlike a static collider, a moving kinematic rigidbody will apply friction to other objects and will “wake up” other rigidbodies when they make contact.

Even when immobile, kinematic rigidbody colliders have different behavior to static colliders. For example, if the collider is set to as a trigger then you also need to add a rigidbody to it in order to receive trigger events in your script. If you don’t want the trigger to fall under gravity or otherwise be affected by physics then you can set the IsKinematic property on its rigidbody.

For detailed information also refer to Unity Manual - Colliders and in particular the sections Collider Interactions and Collision action matrix