Use only the sub categories from a category input

Question

I have a category input. The category group has two levels.

When accessing the category input via Twig I am trying to only grab sub categories the user selected. However when I use

{% set firstCat = entry.categoryInput.first %}
{% set cats = firstCat.getDescendants() %}

or children it grabs all the descendants from Categories > Group not just from the structure that was selected from the input.

Answer 1

You could set the level parameter according to your requirements:

{% set cats = craft.categories({
    relatedTo: {
        sourceElement: entry,
        field: 'categoryInput'
    },
    level: 2,
    limit: null
}) %}

Answer 2

@carlcs helped me stumble upon a solution. Using the .level(2) method gave the desired result.

{% set cats = entry.categoryInput.level(2) %}