Minecraft - Weird spawning behaviour

Question

I am experiencing weird spawning behaviour on my private MC Vanilla Server 1.7.9. Basically we have had 3 different Projects where we encountered this behaviour now. We don't know how to fix it and we don't know why it happens. I hope some of you have an idea!

1. We are currently building a huge and very efficient witch farm based on this video / tutorial:

For that witchfarm we basically followed the tutorial and built it step by step. This is how far we are at the moment: At that point we stopped to see if it works and witches do spawn. However we went about 30 blocks away and hopped into creative. After 10 min nothing happened - not a single witch spawned. 2 hours later I came back alone on the server and what happened? 6 Witches there instanstly! In both cases we have had about 80 Entities around - absolutely normal and witches should have been able to spawn regulary at both times.

After I saw that, I brought my friend back online and we looked into it again. It seems that witches don't respawn if 2 persons are on the server (even when they are in the same area!). The moment my friend went offline 4-6 witches spawned in about 5 sec. At that time we have ad about 90 Entities in the area.

2. The same happens with my big mobfarm. Basically its a HUGE spawnarea way up in the air at ~120. Its built quite good, all is dark and once I am up in the air, mobs can only spawn in that farm. Once two players are online no monsters spawn. Once a player leaves (sometimes) they start spawning and i get a massive amount of drops out of that mobfarm - about a chest full in 10 to 20min. However this only happens sometimes. Very often the farm doesn't work at all. The only time it works is when I'm completely alone on the server.

3. The third farm where this happens is a new gold farm I made way up in the Nether. I basically used the dark oak trick to brake though the bedrock and went up to Y 250. Around there i build some spawn-platforms to see if it works. I do get spawns, don't get me wrong, however the spawns cap at 8 Entities. After that nothing else happens. So i basically paused my gold farm project there.

So in general: We have a very weird spawn behaviour on our rented gameserver. It's vanilla, its SMP and 1.7.9.

What could cause those problems? Why don't our farms work? How can we fix that?

Thanks a lot for your help and ideas! We are playing on that server for more than a halve year now and have build tons of stuff. It would be a shame if those 3 huge farms wouldn't work 100% ...

Answer 1

I was able to talk about my problem to the Creator of the linked Video above myself via Teamspeak.

Here are some things to keep in mind when building a huge farm like that:

• You absolutely need to clear out a HUGE perimeter around the farm to make sure mobs can only spawn in the area you want them to spawn.
• The perimeter around the farm needs to be 128x128. In my case i only cleared out like 50x50 which is by far not enough and the main reason i got extremly low spawn rates compared to JL's video.
• In MC 1.7 and before it is extremly important to notice that the LC Value (as seen in the debug screen) has a huge impact on the farm and spawning behaviour. The LC Value saves for the given chunk how huge the player has builded in this chunk ever since creation of the chunk. For example you go in newly generated terrain at Y = 50 the LC Value will be 50. If you build a 10 high tower on that place the LC will go up to 60. Note that to have good spawning behaviour your LC value needs to be as low as possible.
• Explanation why the LC Value needs to be as low as possible: When MC trys to spawn a Mob in a given chunk, it only will try to spawn it in the area of the chunk under the LC Value. So, if there are several chunks around your farm with a high LC Value, the higher the chance is, that mobs outside of your farm will spawn, because the given chunk actually has more blocks to spawn mobs upon.
• There also is a mobcap on each MC server. So, if you are alone on the server the complete Mobcap will only be taken by you. If there are more players on the server and they even are in different regions, than statistically each player would get halve of the mobcap which means getting halve of the mobspawns.
• There also is a possibility that mobs will be spawned at the edge of the 128x128 perimeter and not despawn instantly due to a bug / feature. JL told me that when a mob is spawned directly at the edge of the 128x128 perimeter and it touches the end of the render distance the game will put this mob into a "sleep" mode thus stopping rendering it. This however causes the mob to still count to the server mobcap while not despawning. Which means it lowers your spawn rate.

This are the reasons i remember, actually JL has told me far more. I convinced him to post a video on that topic on youtube and explane the topic far more in details. The video will come soon from him.

Hope this helps somebody.

Answer 2

It has to do with 1.7.9. just wait for 1.8.x and you wil be fine.