Sorting 8 cuboid points in Python Grasshopper

When we want to make a simple cube using Python in Grasshopper, we can simply use Addbox function in Rhinoscriptsyntax. Just like below.

import rhinoscriptsyntax as rs

#points should be coordinates in (x,y,z) form
point_list = [p1,p2,p3,p4,p5,p6]
rs.AddBox(point_list)

The function takes 8 point lists which consist of the cube that we are going to make. However, important thing is that the point list items should be in the order of the below image to create a normal cube.

Cuboid vertices order

From the below point, the points rotate in reversed clockwise. 

 

Then how can we manage those vertices to be in order? At this point, we need some basic knowledge regarding Python, dealing with sorting lists. The first thing we are going to use is the function sorted() and the second one is the item swap.

 

(1) sorted ( )

list = [1,55,2,8,20,19,23,27,3]
print list

sorted_list = sorted(list)
print sorted_list

[1, 55, 2, 8, 20, 19, 23, 27, 3]
[1, 2, 3, 8, 19, 20, 23, 27, 55]

As you can see on the upper code, the sorted() function automatically returns the list sorted in ascending order. However, sorting points is a bit more complex question. The reason is that there are x,y,z coordinates in our list items. (It is not constructed with a single number like upper example) Then in this situation, what will be our strategy?

import rhinoscriptsyntax as rs

vertice_list = [(0,0,0),(40,0,0),(40,0,40),(0,0,40),(40,40,0),(40,40,40),(0,40,0),(0,40,40)]
a = rs.AddBox(vertice_list)

Error generating box

Using options of sorted() function, we can firstly sort points similar to our intention. 

 

import rhinoscriptsyntax as rs

vertice_list = [(0,0,0),(40,0,0),(40,0,40),(0,0,40),(40,40,0),(40,40,40),(0,40,0),(0,40,40)]
vertice_list = sorted(vertice_list, key=lambda x : x[2])
print vertice_list

a = rs.AddBox(vertice_list)

[(0, 0, 0), (40, 0, 0), (40, 40, 0), (0, 40, 0), (40, 0, 40), (0, 0, 40), (40, 40, 40), (0, 40, 40)]

Using the key option in the sorted function, we can sort a list by the reference we allocated. In the upper example, the list was sorted by z coordinates. However, we still need to sort points, especially orders of vertice_list[4] and vertice_list[5] are switched. In this case, we can use item swap function.

 

(2) item swap

Item swap is a simple and powerful tool when we have to manipulate the order of two items. The syntax is as below. 

import rhinoscriptsyntax as rs

vertice_list = [(0,0,0),(40,0,0),(40,0,40),(0,0,40),(40,40,0),(40,40,40),(0,40,0),(0,40,40)]
vertice_list = sorted(vertice_list, key=lambda x : x[2])
print vertice_list

vertice_list[4], vertice_list[5] = vertice_list[5], vertice_list[4]
print vertice_list

a = rs.AddBox(vertice_list)

[(0, 0, 0), (40, 0, 0), (40, 40, 0), (0, 40, 0), (0, 0, 40), (40, 0, 40), (40, 40, 40), (0, 40, 40)]

Finally, points are sorted as box generating order.

 

(3) Result

Now, the box will be generated with no errors.