Add onEntityCollide function when entity are above a block

[Dhaiven]

Introduction

PocketMine don't have function to detect if an entity are above a block.
So i add a function and fix the bug with magma block.
But there are other bug of this type (with top of cactus...), so i must to be fix in this pr or open an other pr to fix them ?

Relevant issues

Fix #2041

Changes

API changes

Add Block::onEntityCollide()

Follow-up

Tests

Add-Magma-Block-PMMP.mp4

[IvanCraft623]

This does not really check if there is a collision so if there is a slab between the magma block and the player, the player will be burned.

[Dhaiven]

This does not really check if there is a collision so if there is a slab between the magma block and the player, the player will be burned.

Thanks for the feedback, it's fixed

[IvanCraft623]

The current implementation only works for collsions on down side. An appropriate solution to the problem would be to detect when colliding with any face of the block, not just one.

[Dhaiven]

The current implementation only works for collsions on down side. An appropriate solution to the problem would be to detect when colliding with any face of the block, not just one.

Fixed

[ShockedPlot7560]

Look OK to me

[dktapps]

Why is this different for the Y axis than X/Z?

[Dhaiven]

Initially, I started testing with 0.001 for each axis but I found a bug on the Y axis with a slab. Indeed, if you put a block of magma under a slab and a player steps on this slab, with 0.001 on the Y axis, the collision is not detected so I put 0.1 to detect it

[dktapps]

That doesn't make any sense. Is magma supposed to hurt you from underneath a slab? And if it is, why does 0.1 make a difference since the BB of a slab is 0.5 thick?

[Dhaiven]

After some reseach, player take damage on magma block if block between player and magma block has AABB below or equal to 13/16 like trapdoor (https://minecraft.wiki/w/Magma_Block#Damage). So the y value is 1-13/16 = 3/16.

[dktapps]

Then it seems like a collide function isn't appropriate for this. We need something more like onEntityNearby() or onEntityAdjacent().

No longer valid

[ipad54]

My gut instinct is that a better name is probably called for.

How about onEntityStep()?

[dktapps]

Doesn't really fit since it'll be called by a collision from any side.

[Dhaiven]

We also still have hasEntityCollision() from those days

Why not keep this name and call this function just if hasEntityCollision return true ?
Moreover, this can be increase performance

[dktapps]

We also still have hasEntityCollision() from those days

Why not keep this name and call this function just if hasEntityCollision return true ? Moreover, this can be increase performance

Because this will cause unexpected behaviour. No one expected these two functions to be bound together in the first place.

[dktapps]

It looks like what we actually need for this is a function that gets called when an entity is inside an adjacent block. Then, it should be up to the block to decide how much distance is allowed between the entity and the block to apply the effects.