Recommended strategy for overriding certain Rigidbody collisions in Unity?

Question

I'm looking for a little newbie advice on gamedev strategy and/or approach. I'm working on a game that uses Rigidbody physics in Unity and I've got a character interacting nicely with physical objects in the game world. The thing I'm trying to work through is that there are certain physical interactions that I want to control, but my own attempts to control them are conflicting with what Unity is already (correctly) doing.

For simplicity, let's just say I've got a Rigidbody-based player, and when certain Rigidbody-based objects collide with that player, I want to override where they deflect to. When I detect the collision and apply my own force with rb.AddForce(myForceVector, ForceMode.VelocityChange), Unity is also applying it's own force as a result of the same collision. I also tried setting the velocity directly with rb.velocity = myForceVector, which mostly works, but there are still situations where Unity applies force after I set the velocity so it's glitchy at best.

Other options I've considered are:

• Use an additional, larger IsTrigger collision mesh to detect and handler the special type of collision I'm looking for before the actual collision occurs. That might work for slower speed projectiles, but likely will have the same issue for faster collisions.
• Change the player to not being Rigidbody-based, which might work, but would require me to code a lot of the other interactions that are already working out of the box with Rigidbody physics.
• Use RayCasting to detect when these special collisions might occur next and handle them before the actual collision. This is where I'm leaning currently.

Anyone have a recommended best practice for this kind of thing?

Thanks in advance!

Answer 1

The easiest way might just be to take full control. On the correctly timed press, disable the RigidBody and the Collider. Then just move it yourself to the target location. It's really hard to get precise control over a RigidBody -- every FixedUpdate(), it might be picking up force from collisions, and there can be many FixedUpdate() calls between Update() calls.

You could write a pretty simple coroutine using a Lerp() or Slerp() between the object's current and target position. That way, you could fully control how the object moves toward its target.

Answer 2

Just to follow up... I attempted to "take full control" as suggested in Alex M's answer above, but that ended up making a number of other things complicated in my specific situation. However, his comments about disabling the collider in the original question led me down a different path that ended up working well...

I ended up disabling the collider for the deflecting rigidbody upon impact and setting the velocity of the deflected body directly. That way, I was able to avoiding any additional force(s) applied from Unity while the collision was active. Once the deflected object was on it's way, I just had to reenable the collider.

Thanks, Alex!