How to use v.net.path algorithm on QGIS?

Question

I want to use the v.net.path (see grass documentation) from the QGIS processing toolbox. However, I do not know what the format of the input parameters is. The required parameters are:

• Input vector line layer: this is the network
• Center point layer
• Name of file containing start and end point

What exactly must the format of the center point layer be? Which fields should it have?

What exactly must the format of the file with start and end points be?

This question is similar to this unanswered question.

Answer 1

The start/end points is a simple text file with rows for each pair of start/end points. As in the GRASS GIS documentation (that you linked to):

The syntax is as follows:
id start_point_category end_point_category
(Example: 1 1 2)

The "center points layer" refers to a "layer" in GRASS terminology. Any vector "map" in GRASS can have multiple layers, which are, in a way, database connections. This parameter allows to choose which GRASS layer in the node points to use. You can get a better explanation of "layers" in the vector intro section of the GRASS Wiki, (see the section: "Vector object categories and attribute management")

Note that the input parameters needs to be prepared first using v.net.