[MC-4855] Mob spawners miss a row on X and Z axis for the spawn range

I manipulated NBT data a bit to spawn anvils with mob spawners. Problem is they always miss one row on X and Z axis.

As english isn't my native language I made a video showing the issue. It's to large to upload as attachment, so here's a link: https://vimeo.com/55709238

Also I try to explain: Let's say the spawner is at x 6 and z 6. spawn range is 5. The expected output is to add 5 to all sides, so spawn from 0 to 11 on x and z (5 + 1 (the mob spawner) + 5). The given result is 5 + 1 + 4, so from 0 to 10.

BTW: This happens with all entities, anvils are just good to show it. This note is important as it says that this happens with vanilla gameplay, too.

Linked issues

is duplicated by 1

MC-4338 Spawner area not symmetrical Resolved

relates to 2

MC-248225 Incorrect BlockPos getSquaredDistance() calculation Resolved

MC-5215 MobSpawner "MaximumNearbyEntity" Tag only has maximum range of 4 above and 4 below Resolved

Comments 5

bugi74 2013-02-20T09:33:49Z

Possible fix
(Using MCP naming)

TileEntityMobSpawner.updateEntity()

...
    if (var13 != null) {
        var5 = (double) this.xCoord + (this.worldObj.rand.nextDouble() - this.worldObj.rand.nextDouble()) * (double) this.spawnRange;
        var5 += 0.5; // FIX, feel free to combine into the previous line
        double var7 = (double) (this.yCoord + this.worldObj.rand.nextInt(3) - 1);
        double var9 = (double) this.zCoord + (this.worldObj.rand.nextDouble() - this.worldObj.rand.nextDouble()) * (double) this.spawnRange;
        var9 += 0.5; // FIX, feel free to combine into the previous line
        ...

I did not test these changes, but it looks quite obvious.

trazlander 2013-05-27T20:02:59Z

Well hello there bug. You've been around a while.

This is still in the game as of the latest Minecraft version. SpawnRange doubles.
SpawnRange:1 checks 2 blocks outward from the spawner.
SpawnRange:2 checks 4 blocks outward from the spawner.
SpawnRange:3 checks 6 blocks outward from the spawner, etc.

migrated 2013-05-27T20:33:28Z

Confirmed in 13w21b.

Ezekiel 2014-02-03T14:38:51Z

Is this still a concern in the latest Minecraft version 14w05b? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

trazlander 2014-05-27T14:10:10Z

ya it's still around