Minecraft Line Drawing algorithm *Commands*

One Time Run.

/scoreboard players tag @e remove LowestX
/execute @e[tag=LineDraw] ~ ~ ~ scoreboard players operation @e[c=1,tag=LineDraw] OrXL = @e[c=1,tag=LineDraw] OrX
/scoreboard players set LOWEST OrX 2147483647
/scoreboard players operation LOWEST OrX < @e[tag=LineDraw] OrX
/scoreboard players operation @e[tag=LineDraw] OrXL -= LOWEST OrX
/scoreboard players tag @e[score_OrXL=0,tag=LineDraw] add LowestX
/execute @e[score_OrX=2147483647,tag=!LowestX] ~ ~ ~ summon armor_stand ~ ~1 ~ {Tags:["LinePart","LineCon"],NoGravity:1b}
/scoreboard players set 1000 OrX 100000
scoreboard players operation @e[c=1,tag=LineCon] ChangeX = @e[c=1,tag=LowestX] OrX
scoreboard players operation @e[c=1,tag=LineCon] ChangeY = @e[c=1,tag=LowestX] OrY
scoreboard players operation @e[c=1,tag=LineCon] ChangeX -= @e[score_OrX=2147483647,tag=!LowestX] OrX
scoreboard players operation @e[c=1,tag=LineCon] ChangeY -= @e[score_OrX=2147483647,tag=!LowestX] OrY
/scoreboard players set -1 OrX -1
/scoreboard players tag @e[tag=LineCon] add DivideX
/scoreboard players tag @e[tag=LineCon,score_ChangeX_min=0,score_ChangeX=0] remove DivideX
/scoreboard players tag @e[tag=LineCon,score_ChangeX_min=0,score_ChangeX=0] add DivideY
scoreboard players tag @e[tag=DivideY,score_ChangeY_min=0,score_ChangeY=0] add LineEr
execute @e[tag=LineEr] ~ ~ ~ /tellraw @p ["",{"text":"Error ","color":"red","bold":true},{"text":"Line cannot be drawn!","color":"red","bold":false}]
kill @e[tag=LineEr]
execute @e[tag=DivideX] ~ ~ ~ scoreboard players operation @e[c=1,tag=LineCon] YMultSign = @e[c=1,tag=LineCon] ChangeY
execute @e[tag=DivideY] ~ ~ ~ scoreboard players operation @e[c=1,tag=LineCon] XMultSign = @e[c=1,tag=LineCon] ChangeX
/scoreboard players operation @e[tag=DivideX] ChangeY *= 1000 OrX
/scoreboard players operation @e[tag=DivideY] ChangeX *= 1000 OrX
execute @e[tag=DivideX] ~ ~ ~ /scoreboard players operation @e[tag=LineCon] ChangeY /= @e[c=1,tag=LineCon] ChangeX
execute @e[tag=DivideY] ~ ~ ~ /scoreboard players operation @e[tag=LineCon] ChangeX /= @e[c=1,tag=LineCon] ChangeY
/scoreboard players operation @e[tag=DivideX,score_YMultSign_min=1,score_ChangeY=-1] ChangeY *= -1 OrX
/scoreboard players operation @e[tag=DivideX,score_YMultSign=-1,score_ChangeY_min=1] ChangeY *= -1 OrX
/scoreboard players operation @e[tag=DivideY,score_XMultSign_min=1,score_ChangeX=-1] ChangeX *= -1 OrX
/scoreboard players operation @e[tag=DivideY,score_XMultSign=-1,score_ChangeX_min=1] ChangeX *= -1 OrX
/scoreboard players operation @e[tag=LineCon] YTravel = @e[tag=LineCon] ChangeY
/scoreboard players operation @e[tag=LineCon] XTravel = @e[tag=LineCon,c=1] ChangeX
/scoreboard players set @e[tag=LineCon] DrawState 0
/execute @e[tag=LinePoint] ~ ~ ~ setblock ~ ~-1 ~ wool 15

On a Clock (or you know, hit a button repetitively for a long time...)

/execute @e[tag=LineCon] ~ ~ ~ setblock ~ ~-2 ~ wool 15
/scoreboard players operation @e[score_DrawState_min=0,score_DrawState=0] YMove += @e[c=1,score_DrawState_min=0,score_DrawState=0] YTravel
/scoreboard players set @e[score_YMove_min=100000] DrawState 1
/scoreboard players set @e[score_YMove=-100000] DrawState 1
tp @e[score_DrawState_min=1,score_DrawState=1,score_YTravel=-1] ~ ~ ~-1
tp @e[score_DrawState_min=1,score_DrawState=1,score_YTravel_min=1] ~ ~ ~1
scoreboard players remove @e[score_DrawState_min=1,score_DrawState=1] YMove 100000
/scoreboard players set @e[score_YMove=99999] DrawState 0
/tp @e[score_DrawState_min=0,score_DrawState=0,score_XTravel_min=1] ~1 ~ ~
/tp @e[score_DrawState_min=0,score_DrawState=0,score_XTravel=-1] ~-1 ~ ~
/scoreboard players remove @e[score_DrawState_min=0,score_DrawState=0,score_XTravel_min=1] XTravel 1
/scoreboard players add @e[score_DrawState_min=0,score_DrawState=0,score_XTravel=-1] XTravel 1
/execute @e[tag=LowestX] ~ ~1 ~ teleport @e[r=1,tag=LineCon] ~ ~ ~
/execute @e[tag=LineCon] ~ ~ ~ setblock ~ ~-2 ~ wool 15
kill @e[score_XTravel=0,score_XTravel_min=0]

Scoreboards (need to be added in order for this to work)

/scoreboard objectives add ChangeX dummy
/scoreboard objectives add ChangeY dummy
/scoreboard objectives add DrawState dummy
/scoreboard objectives add OrX dummy
/scoreboard objectives add OrXL dummy
/scoreboard objectives add OrY dummy
/scoreboard objectives add XMultSign dummy
/scoreboard objectives add XTravel dummy
/scoreboard objectives add YMove dummy
/scoreboard objectives add YMultSign dummy
/scoreboard objectives add YTravel dummy

-_-Info-_-
I am not responsible for any broken worlds, I just quickly threw this together
I may have misspellde some Scoreboards, for my commands adding them were rudely destroyed
If anything does not work I would be glad to take a look
Coordinates of armor_stands must be kept in OrX and OrY, please no negatives
Does not have to be Minecraft's coordinates
armor_stand points must have Tags:["LinePoint","LineDraw","LinePart"]
must be only 2 armor_stand points.
I may have forgot to list something in this list, get over it.
Chow!