Combine two index numbers

Question content

Background

A

3d cube has 12 sides and 8 angles.

Corner index

8 Corner point indexed 0 to 7.

7---------6
     /|        /|
    / |       / |
   4---------5  |
   |  |      |  |
   |  3------|--2
   | /       | /
   |/        |/
   0---------1

Edge Index

11 Edge has been indexed from 0 to 11.

// these are the corner pairs for the edges:
var mcpairtable = [12][2]int{
    {0, 1}, // edge 0
    {1, 2}, // edge 1
    {2, 3}, // edge 2
    {3, 0}, // edge 3
    {4, 5}, // edge 4
    {5, 6}, // edge 5
    {6, 7}, // edge 6
    {7, 4}, // edge 7
    {0, 4}, // edge 8
    {1, 5}, // edge 9
    {2, 6}, // edge 10
    {3, 7}, // edge 11
}

Combine two index numbers

I want to draw a tetrahedron inside a 3d cube. To describe a tetrahedron, I can use the indices of the sides and angles. For example, a tetrahedron would consist of angles 0, sides 0, sides 3, and sides 8.

question

My problem is the index number. I don't know how to combine the index of the side with the index of the corner. I have two index numbering options.

Option 1: String

One option is to use strings to form the tetrahedrons. For example, I use the c prefix for the corner index and the e prefix for the edge index:

var tehtrahedron = [4]string{"c0", "e0", "e3", "e8"}

But dealing with strings is not as easy as simple integer indexing.

Option 2: Move Index

Another option is to keep the index of the sides from 0 to 11, but move the index of the corners. Therefore, the corner point will be indexed from 0 12 to 7 12, i.e. from 12 to 19. Using this option, the same tetrahedron will look like this:

var tehtrahedron = [4]int{0+12, 0, 3, 8}

or:

var tehtrahedron = [4]int{12, 0, 3, 8}

But this option will mess up the rest of my code and make my code difficult to read.

Comments

1. A tetrahedron does not always consist of 1 corners and 3 sides. Combinations are arbitrary. But the total number of angles and sides is always 4.
2. The index order of the tetrahedron is important.

question

Is there a convenient way to preserve the original index numbers of edges and corners? Is it possible to represent a tetrahedron by the indices of its sides and angles at the same time?

Looking for some ideas...

Correct answer

In the end I chose mobile indexing. The edges are indexed 0 to 11 and the corners are indexed 12 to 19.

I have to do this because the combination of sides and corners is arbitrary. In addition, the order of the indexes is also critical.

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