Minetest_game: 4 glitches in Minetest version 0.4.14

[WSDguy2014]

I found 4 glitches.

1. Any falling sand entities will stuck forever or going to be despawning at any opened fence gate. Must be on NON-SOLID block for all any opening fence gates!
   [EDIT by paramat: Now fixed by #1231 ]
2. Removing a invisible block on all 4 mesh doors (I don't like new mesh doors) and any falling sand entities will stuck forever or going to be despawning.
   [EDIT by paramat: Cannot reproduce the bug]
3. You can break obsidian glass door with bare hand, but on obsidian glass block don't.
   [EDIT by paramat: Now fixed by #1194 ]
4. Any ghost slabs.
   [EDIT by paramat: Now fixed by new slab code]

How to reproduce: https://www.youtube.com/watch?v=WvlIkifyJy4

[tenplus1]

https://github.com/minetest/minetest/pull/4315
https://github.com/minetest/minetest_game/pull/1194

[paramat]

@sofar perhaps you can look at these doors bugs?

The problems with slabs may be improved with #1111

[sofar]

Interesting, I know I checked sand falling onto doors. I'll have to figure out why fence gates are different.

Edit: Item 1 would be an engine bug, not mtg.

[WSDguy2014]

@sofar, can you create a issue for 1st bug from my issue on minetest engine?

[t4im]

Item 1 can also be addressed from mtg.
(although some improvements could be done in builtin to handle some cases better)

The collision box of the open gate is less than 1m high,
that's why the falling node is jerking around so much:
It's falling down, stopped by the collision-box, rounds itself to the node above and starts falling again.

It is also lacking a placeholder node. You can already place a solid node into the open gate and the falling node will solidify.

We could

1. Keep both collision boxes the same size. The node can fall to the ground. This looks colliding, unless the mesh is updated, but so will placing a solid node there right now
2. Add a placeholder node to the fence_gate. It can be made walkable, which will solidify the node. The opening fence needs to handle occupied spaces however.

[paramat]

1. Make gate collisionbox full height?

[t4im]

Make gate collisionbox full height?

That stops the node indeed from moving. But without there being a walkable node below, or the falling node being able to fall down to one, it won't solidify.
Right now the open collision-box hangs into an air node, making it impossible for the falling node to "touch ground".

One could change that behavior in builtin based on monitoring velocity, but that might be error prone and lead occasionally to nodes solidifying mid-air when loading chunks or colliding with other things.

A far harder way around either shrinking the collision-box out of the air node, or occupying the airspace would be an engine change, allowing the lua-api to test for existing collision boxes at a position and then to treat air-nodes with collision-boxes in them like walkable nodes.

[DonBatman]

Just a thought. Since irl putting sand on a fence or gate would result in the sand falling to the ground. Could you add a group to the gate like fall_through = 1. Then have the falling sand fall through the gate and stop at the ground? The sand would have to remain an entity.

[t4im]

For the sand there is no node below it, just air. So no group to check.
There is a collision-box of a node next to it, but its collision is enforced by the physics engine. Reducing the size of the collisionbox (option 1) would be easier, and let it fall, too.

[DonBatman]

My mistake. I still would like my suggestion considered for fences, gates and others.
As for this issue I agree that reducing the collision box would be good.

[paramat]

1. Keep both collision boxes the same size. The node can fall to the ground.

I like this, the fence gate is on the border between 2 nodes anyway and it would be reasonable for loose material to fall either side of it, will make a PR.

[paramat]

See #1231

[jhcole]

1231 only fixed the problem in the -z direction. The collision box for the open fence gate still extends too far in the -x direction.

[paramat]

Oh yeah, will fix.

[WSDguy2014]

@jhcole, this screenshot, texture for fence gate looks like old texture from more tree type mod?

[paramat]

1292 merged.

[WSDguy2014]

In 4th one. In survival mode, you need to hold only any slabs, amount of 2 and try to make a full block now, to produce a ghost slab, if you place another any slab or rejoin world, ghost slab disappear.

[paramat]

Yes we have merged changes to slabs so please recheck that bug.
Are you saying ghost slabs are fixed?

[WSDguy2014]

@paramat, I didn't see, for merged a bug that fixing the ghost slabs.

[paramat]

Tested the remaining bugs, all fixed.