Spatial Transformation
A portal is a window linking to a transformed space. The spacial transformation can be translation, rotation, scale and mirroring.
This mod's teleportation is eye-based. If an entity goes through a portal, it will calculate the entity's eye position transformed by the portal and then place the entity by the transformed eye position.
After crossing a portal with rotation transformation, the player's camera may be tilted. Then the camera rotation will smoothly turn into a valid state.
This mod has special compatibility with Gravity Changer mod. With Gravity Changer mod, if you enable teleportChangesGravity to a portal, then your gravity direction will be automatically changed when crossing the portal. (teleportChangesGravity is disabled by default.)
About Gravity Changer mod: The original author Andrew (Gaider10) have stopped maintaining that mod. After 1.18.1, you can use my fork of Gravity Changer.
This mod has special compatibility with Pehkui mod. With Pehkui mod, if a player or an entity goes through a portal with scale transformation, it will be scaled. This is controlled by the portal property teleportationChangesScale. (teleportationChangesScale is enabled by default)
Mirrors do not allow teleportation.