The bug
Like how random falling damage seemed when it first debuted in 1.3, I'm not sure if this is a bug or a deliberate change to gameplay mechanics, so...
Player launchers are a popular Minecraft invention. Basically, they involve wiring a ring of TNT so it detonates around the player and propels him/her skyward. However, they only work properly in Creative or Peaceful mode. When you switch to Survival on Easy, Normal, or Hard mode, their launching power receives a seemingly arbitrary nerf. A Player Launcher charged with 32 TNT blocks can send you over 300 blocks high in Creative/Peaceful, but on any other difficulty, the height caps out at about 66 blocks for seemingly no reason.
Here's a brand new video showcasing the issue: http://youtu.be/XihAFVogAQ8
Code analysis
Code analysis by @unknown can be found in this comment.
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Yep! This time I recorded a video about the issue as well. Just follow the new link in the description.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
Yes this is still a problem. And I have attached a world save file (TNT Cannon) from the current version (1.6.2) to prove it.
This was from my own issue report, but it describes how the players are being affected more clearly:
"When on Peaceful mode TNT has the capability of launching the player past sky limit. But on easy, normal, and hard modes TNT isn't able to do much; It can't even send players 50 blocks in one direction.
Regardless of survival and creative, this still happens in both game modes. I have attached the following a world compromised of a TNT cannon setup to prove this bug exists. I've tested TNT multiple times with this cannon and the results are the same no matter how the cannon is configured, even in survival and creative. Peaceful is more powerful than the other 3 modes."
And also I can support that no matter how much TNT, even three TNT will only launch you a short amount rather than peaceful mode.
Is this still a concern in the current Minecraft version 1.7.4 / Launcher version 1.3.8 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
Is this still a concern in the latest Minecraft version 14w30c? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
It sure is! I made a new video about it too. https://www.youtube.com/watch?v=uyXdu7z1-E0
It may be more of an unintentional feature than a glitch. It probably has to do with how you take no damage from TNT in creative or peaceful, while in a normal survival situation, simultaneous blasts of TNT can end up canceling each other out a bit and give you less vertical thrust. It's still inconvenient though cause it means a machine like a player launcher functions differently in a creative testing world, so you can't properly gauge how well it will work if rebuilt in survival.
Is this still a concern in the current Minecraft version 1.8.1 Prerelease 3 / Launcher version 1.5.3 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
It's still a concern in 1.9, why does it show "resolved"?
I also found this bug in 1.9! Hope it can be fixed as soon as possible.
Please link to this comment in the description
The following is based on decompiled version of Minecraft 1.9 using MCP 9.24 beta. All method and class names are the names used in the decompiled version.
The reason why this happens is very likely because the damage the player takes counteracts the motion caused by the explosion. This is because a net.minecraft.network.play.server.SPacketEntityVelocity packet is sent and maybe due to the delay between sending and receiving the packet the motion is not correct, but that is only an assumption.
I just tested in 1.10.2: I made five command blocks summon an instantly exploding TNT exactly on me. Tested in Creative and Survival, each difficulty 0 and 1. All tests launched me about 60 blocks up. Is there something wrong with my setup or is this bug fixed?
Unfortunately, i have just tested this in 1.10.2, and i still have the problem. I use a dispenser tnt launcher with 12 tnt's per blast. With survival difficulty >0, i gain ~60 blocks height, whilst survival difficulty 0 gives me around ~190 blocks of altitude.
The setup i use is as follows:
I am standing on a fence surrounded by 8 water blocks in a square. Facing these water blocks are 12 dispensers filled with tnt which will instantly activate when a button is pressed.
Edit:
I've just redone your (Fabian's, see comments) test (as i understood it), and for me it gives the following results:
Survival, difficulty 0:
86 blocks
Survival, difficulty >0
60 blocks
Creative, any difficulty
86 blocks
Fabian, can you respecify your test? It's a bit strange that we get different results while attempting the same experiment.
Again, i'm fairly certain this is a result of the damage calculation. The damage dealt to the player knocks the player and thus slows it down. I believe this should not happen since acceleration happens regardless of how pleasant this is for any entity, and therefore i suggest that all situations should result in the same (86 blocks) result.
I always tested it with resistance 5, because the title is misleading. Changed it now and can confirm it, too.
Can confirm for 1.11
Confirmed for 1.13.1. Please, if you don't mind, I'd like to be the reporter of this issue, I'll update it accordingly.
Confirmed in 1.16 Pre-release 2.
Confirmed in 1.16-pre4.
Confirmed in 1.16-pre5.
Confirmed in 1.16-pre7.
Can confirm in 20w51a.
Can confirm in 21w03a.
Can confirm in 21w05b.
Can confirm in 1.16.5-Optifine_HD_U_G6
Those are not valid on the bug tracker. If you find bugs while playing with Optifine, always verify that they also occur in Vanilla.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.