Player Entity Bounding Box Vertical Offset

For some context, I am working on a reboot of the SmartMoving mod. This mod is using the PlayerAPI and RenderPlayerAPI core mods and are significantly overriding some aspects of the vanilla movement logic. I have been able to resize the player's bounding box by changing player.height (e.g. making the bb less than 1 block high for crawling). However, when I try to offset using a value of bbyOffset != 0, aka translate the bounding box vertically, this actually keeps moving the player in that direction. They will constantly move upwards when I just want to hitbox to be offset vertically and maintain the same movement.

final double d0 = player.width / 2.0D;
AxisAlignedBB aabb = player.getEntityBoundingBox();
player.setEntityBoundingBox(new AxisAlignedBB(player.posX - d0, aabb.minY + bbyOffset,
	player.posZ - d0, player.posX + d0, aabb.minY + player.height, player.posZ + d0));

This is happening on afterOnUpdate(). I know this question is not necessarily a Forge question, but the core mods do not really have a responsive community and my question primarily lies in why the vanilla code is causing this movement.

EDIT: this is being worked on in 1.12.2 currently. I know support for this is over but I believe this would still be applicable for even the newer versions of MC as well.

Edited July 1, 20205 yr by elveskevtar