Trail of particles from a point to TNT

Solution 1:

When you want to start the trail of particles, use this command, with X, Y and Z being the coordinates of the center:

/summon ArmorStand X Y Z {Invisible:1,CustomName:"orb"}

Run these commands, in order, on a repeating/chain command block loop like the depicted:

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ summon ArmorStand ~1 ~ ~ {Invisible:1}

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ summon ArmorStand ~-1 ~ ~ {Invisible:1}  

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ summon ArmorStand ~ ~1 ~ {Invisible:1} 

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ summon ArmorStand ~ ~-1 ~ {Invisible:1}

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ summon ArmorStand ~ ~ ~1 {Invisible:1}

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ summon ArmorStand ~ ~ ~-1 {Invisible:1}

/kill @e[type=ArmorStand,name=orb]

/execute @e[type=MushroomCow,name=Mushy,c=1] ~ ~ ~ entitydata @e[type=ArmorStand,c=1] {CustomName:"orb"}

/kill @e[type=ArmorStand,name=!orb]

/execute @e[type=ArmorStand,name=orb] ~ ~ ~ /particle cloud ~ ~ ~ 0 0 0 0.02 3

/execute @e[type=MushroomCow,name=Mushy,c=1] ~ ~ ~ kill @e[type=ArmorStand,r=1]

A screenshot:

It has been brought to my attention that this method is rather slow. A way to speed it up is simply to make another set of command blocks as below:

I have tested both the functionality and the speedup method and they seem to work. However, if you try it and find a problem, please tell me and I will look into it.

Solution 2:

Minecraft has a command for spawning particles (/particle). The wiki page for this command is mentioned here. This allows spawning particles which has been added in 1.8. Through searching myself. I have found this command block tutorial which gives a few command examples:

/particle name (particle pos x) (particle pos y) (particle pos z) (particle size x) (particle size y) (particle pos z) (time of particle) (amount of particles or density) (target)

The variables X Y and Z are the starting position and XD YD and ZD are the direction it's going in. So in your case it should be:
/particle smoke ~ ~ ~ 1 1 1 0.01 100 @e[name=""]

Smoke is your effect aka the torch effect. The three ~'s is the target's position which is mentioned at @e[name=""]. It will be best to name your mooshroom for easier targeting.

EDIT: /execute @e[name=Mushy] ~ ~ ~ /particle cloud ~ ~ ~ 0 1 0 0.02 100 This worked for me. I spawned a mooshroom called Mushy and this spawned particles on Mushy. I've noticed that the command block has a certain range, so make sure that it's in the range.