8.3 Drawing at different scales

We saw how to draw a square, and a rectangle with different sides. Now, we return to our house example p. and we’re going to modify the code to draw this house at any chosen scale.

The objective is to send an argument to the procedure house and according to this parameter, the house will be smaller or bigger.

In real size, the procedure square was:

to square  
repeat 4 [forward 150 right 90]  
end

All the initial dimensions are multiplied by the scale. Hence, the procedure square becomes:

to square :c  
repeat 4 [forward 150*:c right 90]  
end

Therefore, when we’ll write square 2, the square will have for side length 150 × 2 = 300. Proportions are well respected! In fact, we can see that we just need to modify all procedures replacing the length according to this rule:
fd 70 becomes fd 70*:c
fd 45 becomes fd 45*:c

to carre :c  
repeat 4[forward 150*:c  right 90]  
end  
 
to tri :c  
repeat 3[forward 150*:c right 120]  
end  
 
to porte :c  
repeat 2[forward 70*:c right 90 forward 50*:c right 90]  
end  
 
to che :c  
forward 55*:c right 90 forward 20*:c right 90 forward 20*:c  
end  
 
to dep1 :c  
right 90 forward 50*:c left 90  
end  
 
to dep2 :c  
left 90 forward 50*:c right 90 forward 150*:c right 30  
end  
 
to dep3 :c  
penup right 60 forward 20*:c left 90 forward 35*:c pendown  
end  
 
to ma :c  
carre :c dep1 :c porte :c dep2 :c tri :c dep3 :c che :c  
end