In the previous example the tunnel was horizontal so the value of y for the tunnel was always constant. To make the tunnel route more complicated without having duplicate code we define a function called tunnelvertical(eastposition). For any value of the east position (x value) this function will return the vertical position of the tunnel.

def tunnelvertical(eastposition):
    y = abs(100 - (eastposition - XMIN))
    if y < 10:
        return 10
    if y > 72: 
        return 72
    return y

XMIN is a constant we have previously defined in the code showing where the tunnel starts. The shape of this tunnel is horizontal at ground level, then slopes down until it reaches level 10, goes horizontal for a while, then slopes up until it reaches ground level again and finishes off horizontal.

Here is the full code

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
XMIN = -400 # x value at one end of tunnel.
XMAX = -200 # x value at other end of tunnel. Must be greater than XMIN
GROUND = 72 # y position of tunnel at each end
FLOOR = 10  # minimum value of y at bottom of tunnel
ZPOS = -222 # z position for full length of tunnel
TAIL = 10   # length of horizontal at each end of tunnel

# constants for tunnelvertical function
kx = (XMAX + XMIN) / 2
ky = GROUND + TAIL - (XMAX - XMIN) / 2

# tunnelvertical returns a vertical position of the tunnel
# for each value of the x position (eastposition)
def tunnelvertical(eastposition):
    y = abs(eastposition - kx) + ky
    if y < FLOOR:
        return FLOOR
    if y > GROUND: 
        return GROUND
    return y

# set the z coordinate for the tunnel which doesn't change for the full length    
z = ZPOS

# Initial loop to create a route made of solid glass with a stone base 
for x in range(XMIN,XMAX+1):
    y = tunnelvertical(x)
    mc.setBlocks(x,y,z-2,x,y+6,z+2,block.GLASS)
    mc.setBlocks(x,y,z-1,x,y,z+1,block.STONE)

# Second loop to convert solid glass into a tunnel
for x in range(XMIN+1,XMAX):
    y = tunnelvertical(x)
    # replace centre glass with air to make it a tunnel
    mc.setBlocks(x,y+1,z-1,x,y+5,z+1,block.AIR)
    # place a torch every 4 positions to light the tunnel
    if x % 4 == 0:
        mc.setBlock(x,y+1,z+1,block.TORCH.id,5)

In the previous example the tunnel was glass all around. To make a more interesting tunnel this example adds a stone floor and adds a torch. We will develop this tunnel in two stages. The first stage is to create a profile showing what a cross-section of the tunnel will look like for any value of x.

nano tunnelprofile2.py

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
x = -190
y = 72
z = -222
mc.setBlocks(x,y,z-2,x,y+6,z+2,block.GLASS)
mc.setBlocks(x,y,z-1,x,y,z+1,block.STONE)
mc.setBlocks(x,y+1,z-1,x,y+5,z+1,block.AIR)
mc.setBlock(x,y+1,z+1,block.TORCH.id,5)

python3 tunnelprofile2.py

The second stage is to create a loop to draw each cross section of the tunnel at each value of x between xmin and xmax. Note that at the ends we ant the wall of glass to stay so that lava and water don’t flow into the tunnel should it get built next to these liquids. We have achieved this with two loops. The first loop goes the full length of the tunnel from xmin to xmax. The second loop which adds air and torches starts and ends one position in from the ends. Torches are added every 4 positions by using the modulo (%) operator.

nano stonefloortunnel.py

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
xmin = -224
xmax = -200
y = 72
z = -222
for x in range(xmin,xmax+1):
    mc.setBlocks(x,y,z-2,x,y+6,z+2,block.GLASS)
    mc.setBlocks(x,y,z-1,x,y,z+1,block.STONE)
for x in range(xmin+1,xmax):
    mc.setBlocks(x,y+1,z-1,x,y+5,z+1,block.AIR)
    if x % 4 == 0:
        mc.setBlock(x,y+1,z+1,block.TORCH.id,5)

python3 stonefloortunnel.py

Creating a hollow tunnel with walls at each end

To create an air space in the tunnel we can use another loop. However, the second loop should not go all the way to the ends because we want walls at each end. This is to stop water and lava flowing into our tunnel should the ends of the tunnel meet these liquids.

nano hollowglasstunnel.py

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
xmin = -224
xmax = -200
y = 72
z = -222
for x in range(xmin,xmax+1):
    mc.setBlocks(x,y,z-2,x,y+6,z+2,block.GLASS)
for x in range(xmin+1,xmax):
    mc.setBlocks(x,y+1,z-1,x,y+5,z+1,block.AIR)

python3 hollowglasstunnel.py

Our next exercise it to create a tunnel of glass filled with air. Glass is useful because it is transparent. To start with the tunnel will be horizontal heading east which means the x coordinate will be increasing and the y and z coordinates will keep constant values. We could use the setBlocks command for the entire length of the tunnel. However we want to keep the code flexible enough that later on the tunnel could start ascending or descending, i.e. the y coordinate could start increasing or decreasing. The profile of the tunnel which will be a wall of glass 5 blocks across and 7 blocks high. Here is the code to create a profile of the tunnel for one value of the x coordinate.

nano tunnelprofile.py

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
x = -200
y = 72
z = -222
mc.setBlocks(x,y,z-2,x,y+6,z+2,block.GLASS)

python3 tunnelprofile.py

A loop can be added which will draw the profile of the tunnel over and over again for a range of different x values. Note how important indentation is in python. I am indenting 4 spaces when in a loop.

nano solidglasstunnel.py

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
xmin = -224
xmax = -200
y = 72
z = -222
for x in range(xmin,xmax+1):
    mc.setBlocks(x,y,z-2,x,y+6,z+2,block.GLASS)

python3 solidglasstunnel.py

The previous example showed that python scripts could quickly become very long if each block had to be set individually. Fortunately there is the setBlocks command which can set many blocks at once. It also has two forms.

mc.setBlocks(x1,y1,z1,x2,y2,z2,block)
mc.setBlocks(x1,y1,z1,x2,y2,z2,block.id,variation)

The minecraft coordinates (x1,y1,z1) represent one corner of the rectangular prism about to be set. The minecraft coordinates (x2,y2,z2) represent the diagonally opposite corner. The previous example can be rewritten to use the setBlocks command. The glass is set first otherwise it would overwrite the setting of the middle block. In this example the middle block is air which is equivalent to there being no block.

nano placeglassblocks.py

import mcpi.minecraft as minecraft
import mcpi.block as block
mc=minecraft.Minecraft.create()
mc.setBlocks(-220,72,-223,-218,74,-221,block.GLASS)
mc.setBlock(-219,73,-222, block.AIR)

python3 placeglassblocks.py