[1.12.2] Collision box that only allows passing through in one side

[Aarilight]

I'm making Yet Another Spike Block and I think it would be unique if you collided with all sides except for the pointy side. (It looks kinda like punji sticks)

 

Can you manipulate collision boxes to do something like this or is that not possible?

[jabelar]

It depends on exactly what you mean in terms of how it would look. But if it would look like a slab with some pointy sticks on it, then if you make the bounding box just to cover the slab portion then it should work pretty well.

 

I can't think of an easy where where the collision block changes based on the way the player enters though. The getCollisionBox() method only takes in information about the block, not about whatever is trying to process the collision box. So it is probably best to not make it dynamic, but instead make a fixed slab that is part of the block. 

[Aarilight]

Based on the design for it, that's not something I can do. See attached image.

You said you can't think of an easy way to do what I want, but that's okay, I don't necessarily need it to be easy. If you have any ideas, can you point me in the right direction?

Edited December 27, 2017 by Aarilight

[American2050]

6 hours ago, Aarilight said:

Based on the design for it, that's not something I can do. See attached image.

You said you can't think of an easy way to do what I want, but that's okay, I don't necessarily need it to be easy. If you have any ideas, can you point me in the right direction?

So, if you walk across you don't receive damage, but if you fall from the top yo do?

Could it be possible to check where the entity is moving towards (or coming from) and use that to determine damage? Not sure if that could go on the block itself, or if it would have to be on some event.

Edited December 27, 2017 by American2050

[Aarilight]

It can face in any direction. In the example since it's pointing up, it would be safe to walk into it because you would collide with it, but not safe to fall down onto it. It would work the same if it was pointing down, and similar to the side, as then you'd be able to stand on the spikes but not walk into them from the side they're facing.

I know sorta the logistics of how it would work if I had implemented my own movement/collision system, but I did not write minecraft and so I'm not sure where to begin, hah.

Edited December 27, 2017 by Aarilight

[Draco18s]

If you make the collision box a full cube in all directions except up, then you can use the same code that cactus does for damaging the player, which is based on the player's collision box being inside the full 1x1x1 volume of the block.

 

This will allow the player to grind themselves up against the sides the spikes without taking damage.

[Aarilight]

How would I make a collision box that is missing a face? AxisAlignedBB only takes the corner coordinates? Am I missing something?

[Draco18s]

...make it SMALLER than 1x1x1

 

Like... 1x0.9x1

 

It still HAS a top face, but that when the player stands there, they will take damage.

[Aarilight]

Ah, yea, that was the first thing I tried. I wasn't a giant fan of it, based on the texture (I suppose I can just change that tho). I did actually manage to get it to work, just when it's facing up, with some crazy calculations. I might go through and add detection for the other directions, but it's a lot of trial and error and it may not even end up working right, so I'm not sure if it's worth it.

If anyone is curious here's what it looks like: https://puu.sh/yPevw/74480107a3.mp4

And you can see how I did it here: https://github.com/Yuudaari/soulus/blob/master/src/main/java/yuudaari/soulus/common/block/Skewer.java#L106-L160

[jabelar]

Actually, the way to do this is to override the addCollisionBoxToList() method. In the past I have made the collision box change based on the entity that was colliding with it. The cool thing about this method is it passes the entity. I guess you could look at the entity motion and compare with the facing direction to declare a collision (and then have the collision do damage).

 

EDIT: Just saw you posted while I was writing this and looks like you indeed did use that method. Cool.

Edited December 28, 2017 by jabelar