General Physics Feedback

I’ve spent a bit of time with some of the new Physics features and I’m loving them. Here's some feedback.

Kinematic Contacts
Best feature by far for me is kinematic contacts. I’ve been waiting for something like that since the 2D physics was announced. I can finally get collision data without the physics system reacting to the collision. This makes it way easier to program 2D platformers that don’t have realistic physics.

I noticed that the normal impulse property of the contacts of a kinematic body collision are 0. If I wanted to simulate a regular collision reaction, is there a way for me to do it? Then I would basically be able to determine whether objects react to physics after a collision occurred. I tried using the normal with the edge separation, and it seemed to work alright, but was not perfect. I am mainly asking because I thought it might be an easy way to position my character on top of ground and stuff like that. I usually just get the actual position of the top of the collider and put my character on top of it.

Edge Radius
The edge radius seems to add some possibilities, but I am wondering if there is a more intuitive way to size things in the editor? If I wanted to have a BoxCollider of size 1, but I want the corners to be rounded, it seems hard to get that sized correctly. What if the property was just called roundness, and it would keep the box the same size, but would just round the corners? This seems like it would also work on a polygon collider, but on edge collider it would still need to be called radius since they have no size by default. Just a thought.

LateFixedUpdate
Please try to convince Unity to add a LateFixedUpdate callback. This will be useful for some of the new API you've included, like Physics2D.GetContacts. If we want to always make sure the info from those is accurate, we'd need a callback for after all physics have been simulated. I want the callback so I can check on things and make sure nothing is wrong with my bodies and colliders. There is currently no way to get a callback after all OnTrigger and OnCollision methods have fired. This has caused me much strife.

Other Notes:

• New casting stuff looks good and useful
• Isn't it redundant to have some of the same methods in two places, like how GetContacts is on both Physics2D and Rigidbody2D/Collider2D? Seems to make more sense just being on Rigidbody2D/Collider2D
• Is there any way to get both colliders in a trigger collision, like in OnTriggerEnter2D? I've always found it annoying only one collider is included, and I've had to do weird things with game objects to be sure I knew which colliders were hitting. Can you add this if it's not included already?
  
• Radius seems like a good fit for PolygonCollider2D as well
• I like the new ContactFilter2D struct. Reduces clutter.
• New Physics2D gizmos in editor are awesome. Saved me lots of time already.
• Isn't edge collider with a radius the same thing as a capsule collider?

I mainly just use the physics2D stuff for collision detection and control stuff myself, so I've never used effectors or joints and can't give feedback on them.

 

I would prefer updating the position/rotation manually if I had to choose between them. This gives more control, and allows you to do things like simulating the trajectory of a grenade without actually modifying the position of anything.

Sounds good. I personally always thought it would be more useful to have callbacks that are actual C# events instead of Unity's message things. So you would use it like this:

Code (CSharp):

1. GetComponent<BoxCollider2D>().OnCollisionEntered += collision => {
2.     Debug.Log(collision);
3. };

I just meant in the editor it would make things easier, even if it's only available in the edit collider mode. (Although I personally also like the option of entering it in a field.) If I had the algorithm I'd probably just write a custom inspector to add the field. On Box collider, I added fields for adjusting size and position from the bottom left because I do that quite often.

Sounds good. My guess is you improved it to make it easier on yourself to build the tile map collider.

People may get confused by edge colliders not hitting each other in the future when they forget the time that they existed without a radius.

Either way you need the instance so why not just have it on the instance? Not a big deal. Just sayin'.