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Based on this video. I tried to make this kind of rocket launcher for my mini game.

I Used this command:

/execute @e[type=Snowball] ~ ~ ~ /summon Fireball ~ ~ ~ {Motion:[0.0,0.0,0.0],direction:[0.0,0.0­,0.0]}

but I got:

unable to summon object.

I used the 15w51b snapshot. I think I also tested this a while back in 1.8 but i can't remember if it worked

1 Answer 1

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No.

I just did some testing in 1.8.9, as well as the 1.9 snapshots 15w51b and 16w03a. Fireball (and SmallFireball) require you to specify the direction tag (the Motion tag is not needed!), see the invalid "bug" MC-86011. In 1.8.9, a Fireball without direction will simply vanish immediately. In the snapshots/1.9, the direction tag is more strict: It needs to exist, and needs to contain exactly 3 doubles. Otherwise, you'll will get a message saying "Unable to summon".

In any case, if a direction tag is correctly specified, the object will be summoned.

Now the problem you are having is that there is a strange hidden character in your direction tag, which can be seen when you copy-paste the command into Minecraft (SE doesn't show it at all):

hidden character as seen in Minecraft

This character causes Minecraft to think the second entry of the tag is a string rather than a double, and Minecraft promptly throws it out. Your direction tag now has only 2 entries and is therefore invalid, which causes your problems. You can copy-paste this command instead:

/execute @e[type=Snowball] ~ ~ ~ /summon Fireball ~ ~ ~ {direction:[0.0,0.0,0.0]}

Thanks to @Skylinerw for explaining the technical details.

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  • Just to clarify for differences between 1.8/19: direction must exist in 1.8 for the fireball to not be deleted instantly when summoned and can contain any data, but in 1.9 it must exist and contain 3 Doubles, no more or less. In his original NBT, since the root type of the direction was declared as a Double, all the remaining records must be the same type. Because the Soft Hyphen character causes the second record to be a string, it gets thrown out, and thus the list only contains 2 Doubles.
    – Skylinerw
    Jan 26, 2016 at 12:22
  • @Skylinerw Oooh, technical details, very nice. I tried to incorporate your comment into the answer, can you just double-check if it's correct and/or edit if not?
    – MrLemon
    Jan 26, 2016 at 12:57
  • Yep, looks good!
    – Skylinerw
    Jan 26, 2016 at 14:04

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