How to check if a player is looking at a player?

How do I check if player1 can see player2 and how to establish player2 as a 'Player player2 = #####'?

 

Trevor1134
Quite hard to achieve, but what i'd suggest doing is get the block the player is looking at, then subtract that location from the players location to get a direction vector. Then 'travel along' this vector checking if a player is within a few blocks at each stage, this should give you a broad idea of whether a player is in someone's crosshairs but it's far from accurate.

 

chasechocolate did something like this, but with mob entities. Maybe he could help

 

This is what I originally used:

Code:java

    private LivingEntity getEntityInLineOfSight(Player player){
        Block targetBlock = player.getTargetBlock(null, 50);
        Location blockLoc = targetBlock.getLocation();
        double bx = blockLoc.getX();
        double by = blockLoc.getY();
        double bz = blockLoc.getZ();
        List<Entity> nearby = player.getNearbyEntities(100, 100, 100);
 
        for(Entity entity : nearby){
            if(entity instanceof LivingEntity){
                Location loc = entity.getLocation();
                double ex = loc.getX();
                double ey = loc.getY();
                double ez = loc.getZ();
 
                if((bx - 1.5 <= ex && ex <= bx + 2) && (bz - 1.5 <= ez && ez <= bz + 2) && (by - 1 <= ey && ey <= by + 2.5)){
                    return (LivingEntity) entity;
                }
            }
        }
 
        return null;
    }

However, this sometimes will not work. Using Comphenix 's Vector3D class (from this: http://forums.bukkit.org/threads/allow-invisible-hidden-players-to-be-attacked.114668/), you can do it this way:

Code:java

    private Entity getEntityInSight(Player player){
        Location playerLoc = player.getLocation();
        Vector3D playerDirection = new Vector3D(playerLoc.getDirection());
        Vector3D start = new Vector3D(playerLoc);
        Vector3D end = start.add(playerDirection.multiply(scanDistance));
        Entity inSight = null;
 
        for(Entity nearbyEntity : player.getNearbyEntities(scanDistance, scanDistance, scanDistance)){
            Vector3D nearbyLoc = new Vector3D(nearbyEntity.getLocation());
 
            //Bounding box
            Vector3D min = nearbyLoc.subtract(0.5D, 0, 0.5D);
            Vector3D max = nearbyLoc.add(0.5D, 1.67D, 0.5D);
 
            if(hasIntersection(start, end, min, max)){
                if(inSight == null || inSight.getLocation().distanceSquared(playerLoc) > nearbyEntity.getLocation().distanceSquared(playerLoc)){
                    inSight = nearbyEntity;
                }
            }
        }
 
        return inSight;
    }
 
    private boolean hasIntersection(Vector3D start, Vector3D end, Vector3D min, Vector3D max) {
        final double epsilon = 0.0001f;
 
        Vector3D d = end.subtract(start).multiply(0.5);
        Vector3D e = max.subtract(min).multiply(0.5);
        Vector3D c = start.add(d).subtract(min.add(max).multiply(0.5));
        Vector3D ad = d.abs();
 
        if(Math.abs(c.getX()) > e.getX() + ad.getX()){
            return false;
        }
 
        if(Math.abs(c.getY()) > e.getY() + ad.getY()){
            return false;
        }
 
        if(Math.abs(c.getZ()) > e.getX() + ad.getZ()){
            return false;
        }
 
        if(Math.abs(d.getY() * c.getZ() - d.getZ() * c.getY()) > e.getY() * ad.getZ() + e.getZ() * ad.getY() + epsilon){
            return false;
        }
 
        if(Math.abs(d.getZ() * c.getX() - d.getX() * c.getZ()) > e.getZ() * ad.getX() + e.getX() * ad.getZ() + epsilon){
            return false;
        }
 
        if(Math.abs(d.getX() * c.getY() - d.getY() * c.getX()) > e.getX() * ad.getY() + e.getY() * ad.getX() + epsilon){
            return false;
        }
 
        return true;
    }