2D platform physics collision jitter

[rick551a]

Godot version: 3.2.4 beta6 (mono)

OS/device including version: Win10 Nvidia 1650

Issue description:

Tested a simple 2d platformer, the player is unable to jump and continually jitters up and down, almost through the ground.

Worked fine in 3.2.3 (stable) mono.

Steps to reproduce:
Open project, run, move left right, try to jump.

Minimal reproduction project:
This simple project by heartbeast:
https://github.com/uheartbeast/simple--heart-platformer

[Calinou]

@rick551 Can you reproduce this in 3.2.4beta5?

cc @pouleyKetchoupp

[pouleyKetchoupp]

Confirmed regression from #42574.

[rick551a]

Apologies for late reply, the issue was not in 3.2.4beta5.

[pouleyKetchoupp]

@rick551a Could you check that everything works ok again if you set a safe margin of 0.01 on the KinematicBody2D?

When working with pixel art / low screen resolution, the scale you use for motion is lower (including gravity), so a lower safe margin is needed for collision algorithms to work properly.

There used to be a workaround in move_and_slide that helps with floor detection in this case, even with the default safe margin, but it had to be removed as part of #42574 because it was causing issues in some other cases.