out of bounds check too strict

Shouldnt the out of bounds check be inclusive of the maximum indices?

So
```
if x0 >= 0 and y0 >= 0 and z0 >= 0 and x1 <= X and y1 <= Y and z1 <= Z:
```
instead of
```
if x0 >= 0 and y0 >= 0 and z0 >= 0 and x1 < X and y1 < Y and z1 < Z
```
?