Floating point comparison issues with bounding boxes

[dktapps]

Issue description

Due to the impossibility of completely accurately representing most fractional numbers as floats, they should not be compared directly. However, PocketMine-MP does this in many places - most notably in AxisAlignedBB->intersectsWith()

This is problematic because this means that any floating point error, no matter how small, will result in issues with false intersections.

Take the following example: A block with BB minY=6, maxY=7. Then you have a player standing on top of it trying to place a block next to it. Their bounding box minY is apparently 7 according to var_dump(), but raising the precision php.ini directive shows us that their BB is actually something like 6.99999999999999911182158029987476766109466552734375. This tiny difference causes the player not to be able to place blocks on the same Y coordinate while standing on top of an already placed one.

This comparison should be using epsilons to compare BB bounds for intersection.

Performance must be considered for any fix applied for this because BB intersection is a heavily-used function.

Steps to reproduce the issue

1. place a block
2. jump on top of it and stand on its edge
3. try to place a block on the same level as it while standing over the space

OS and versions

• PocketMine-MP: ddc9dca
• PHP: 7.2.2
• Server OS: linux

[dktapps]

Fixed in #2101 .