No 100% accurate physics/collision handling

Questions & Answers
1

I am new to Unity and experimenting the last few weeks, trying to create a 2D concept I had in mind. In those experiments I found out that the Physics engine is not 100% accurate, especially in collision handling, creating a few problems in my project. In the following video (only 14 seconds, don’t worry) I have two cubes, one scaled in x-axis acting as floor, and the second one with a rigibody attached waiting to fall on the floor.

1

In order to create the 2D setup I have activated the FreezePositionZ, FreezeRotationX and FreezeRotationY constrains. The problem that I encounter is that the cube doesn’t end up in the position that it should (x=0, y=1, z=0, x-y-z-rotation=0). As you can see in the image below the position-y = 0.98 and rotation-z=0.001 (never mind the position-x for now).

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I have found a way to minimize the position-y difference (Edit->Project Settings->Physics->Min Penetration for Penalty = 0), but not to make it be exact 1, as it should. The main problem now is the z-rotation.

I am using the most simple primitive shapes, I find it very strange that the engine doesn’t do a better job in collision handling. Is there any way to get the proper values?

Thanks in advance!

2

If you want precise positioning, forget about physics. In all game engines, the physics engine is intended to simulate real world physics, which includes some amount of uncertainty: anytime you let the rigidboy fall to the floor, for instance, it will bounce and stop in a slightly different angle - just like in real life.

If you really need precision, remove the rigidbody and handle its positioning, rotation and movement by script - you will have precision, but the object will not detect collisions.
Another alternative is the CharacterController: it’s not under physics control, but detects collisions, and is used mostly in characters.