Using AABB to get a entities

[UberAffe]

This is what I am doing currently

int range = myItem.getRange();
BlockPos pPos = player.getPosition();
Vec3d look = player.getLookVec();
BlockPos tPos = pPos.add(new Vec3i(pPos.getX() + look.xCoord*range, pPos.getY()+ (look.yCoord*range), pPos.getZ() + (look.zCoord*range)));
List<Entity> targets = player.worldObj.getEntitiesWithinAABBExcludingEntity(player, new AxisAlignedBB(pPos, tPos));

but it only seems to work when I am facing a certain direction, I think it's north-east.

So two questions:

Any idea why this only seems to work in 1 general direction?

Is there another method or ordering to the entities returned that would allow me to get just the closest entity without doing a bunch of other calculations.

[Draco18s]

Well.

 

Imagine for a moment that your lookvec is (1,0,0)

[UberAffe]

It should get me a tPos that is the distance of range away from pPos in the x direction.

 

Unless I misunderstood what look.xCoord is returning it should be a double that is in the range of -1 to 1.

[Draco18s]

  On 4/1/2016 at 2:18 AM, UberAffe said:

It should get me a tPos that is the distance of range away from pPos in the x direction.

 

Yes, and how large of a volume will the AABB between pPos and tPos be?

[UberAffe]

I'm guessing that means it gets all entities in the cube created by the two positions and not just entities that intersect the line between the two positions.

[coolAlias]

You're misunderstanding vectors and aabb: the look vector is normalized, so all values are between -1 and 1. If the player is looking straight up or down, x and z coord of look vec are both zero, so:

pPos.getX() + look.xCoord*range

which equals: pPos.getX() + 0 * range
which equals: pPos.getX()

So aabb is between pPos.getX() and... pPos.getX(). A horizontal plane of nothing, basically.

 

That, however, is not the issue. The issue is that you are adding the player's position to itself. Vectors are additive, so (x, y, z).add(x1, y1, z1) becomes (x + x1, y + y1, z + z1).

 

Now imagine you are standing at 1000, 60, -500, looking straight west so your look vector is (-1, 0.5, 0) or something like that. Even with a range of 20, the look vector becomes irrelevant compared to the position. Let's take the xCoord for example:

pPos = 1000

tPos = 1000 + (1000 + (-1 * range)) = 1980, for example

aabb checks for entities between x=1000 and x=1980, which is EAST of your position (very very far east), even though you are looking WEST.

 

Now apply that to all 3 directions; see why you are not getting what you expect?

 

Solution: don't include pPos in the tPos calculations.

[UberAffe]

Right. Somehow I managed to ignore the face that I was using the add method to get the new position, which resulted in the players position getting effectively doubled.

 

Second question stands: is there a way to get only the nearest entity that intersects without checking the distance of all of them?

[coolAlias]

  On 4/1/2016 at 4:02 AM, UberAffe said:

Second question stands: is there a way to get only the nearest entity that intersects without checking the distance of all of them?

No, that is literally impossible. You can't know which is the nearest without checking all options, though some methods like #findNearestPlayer and such may make it seem like you don't have to check because you are not making the comparisons in your own code.

[UberAffe]

I know it has to happen somewhere but I was curious if it was already happening somewhere so that I wouldn't be writing duplicate (probably less efficient) code.

[coolAlias]

It's not happening with the method you have chosen, no, but there are methods that filter for you, and in 1.9 there are probably even some that accept a Predicate allowing you to custom filter the results. I don't have Forge / MCP on this computer, so I can't tell you any more specifically than that.

[Draco18s]

World#doRaycast

[coolAlias]

  On 4/1/2016 at 6:24 AM, Draco18s said:

World#doRaycast

IIRC, doesn't ray tracing only find blocks, not entities? Or is #doRaycast something completely different?

[Draco18s]

Raycasting can detect enemies, sure.  I don't recall offhand which method needs to be called, there's at least two.

[UberAffe]

I couldn't find any raycast methods in player.worldObj, I found three methods that were variations of rayTraceBlocks with different params. Although #findNearestEntityWithinAABB seems to be doing what I want.

[Draco18s]

findNearestEntityWithinAABB will work, provided that the volume is actually large enough to contain anything.

 

Anyway, looking up my old artifacts code, the method I used was

rayTraceBlocks_do_do

which did hit entities.

https://github.com/Draco18s/Artifacts/blob/master/main/java/com/draco18s/artifacts/network/PacketHandlerServer.java#L160

[UberAffe]

                                float range = ((float)item.partMap.GetHeight())/16.0f + 1.5f;
			Vec3d pVec = player.getPositionEyes(.5f);
			Vec3d tVec = pVec.add(player.getLookVec().scale(range));
			LogHelper.info("Player is at " + pVec);
			LogHelper.info("Target is at " + tVec);
			RayTraceResult target = player.worldObj.rayTraceBlocks(pVec, tVec,false, true, false);
			LogHelper.info(target.typeOfHit);

This is the call I am using and pVec/tVec have a value for each Coord, but the last line always has a null pointer exception. Even with hard coding the range to 10 it always gives null.

 

Edit: Slight wrong, If I aim at an entity and there is nothing behind it but air I get NULL.

If I aim at an entity and there is a block behind it I get Block . Which seems like it doesn't work for entities anymore.